Final Report Summary - IBPOWER (Intermediate band materials and solar cells for photovoltaics with high efficiency and reduced cost) Executive summary: Our proposal investigated the practical implementation of the intermediate band solar cells (IBSCs) pursuing strategies of high efficiency and low cost. An IBSC consists of an 'intermediate band material' sandwiched between two conventional semiconductors of p and n type. The 'intermediate band material', that gives the name to the solar cell, is characterised by the existence of a collection of energy levels (intermediate band, IB) located between the conduction and valence bands (CB and VB). This IB divides the semiconductor bandgap EG into two bandgaps EL and EH. The potential of this cell is equivalent to a three-junction solar cell but without the requirement for tunnel junctions. Its practical implementation requires: 1. an IB material, to which it is possible to manufacture appropriate contacts (the p and n emitters) 2. the absorption of two sub-bandgap photons in the sense of one photon pumping an electron from the VB to the IB and a second photon pumping an electron from IB to the CB. It is this two photon absorption process (which it is not a simultaneous three particle collision process) that allows the extraction of a higher current when compared to the operation of single gap solar cells 3. carrier relaxation between bands has to occur at a much lower rate than carrier relaxation within bands. This is normal in conventional semiconductors and in the IBSC allows for the existence of three distinguishable quasi-Fermi levels associated with each of the bands (EFC, EFI and EFV for the CB, IB and VB respectively). Since the output voltage of the cell is related to the difference between electron and hole quasi-Fermi levels and this difference is set by the emitters, the output voltage of the cell is still limited by the largest of the bandgaps EG. This allows for the extraction of the higher current arising from the additional two photon generation process without voltage degradation. Project context and objectives: Using energy levels inside the bandgap to increase the efficiency of solar cells was first analysed by Wolf (M. Wolf, Proc. IRE ; Vol/Issue: 48:7, pages: 1247 (1960)) in 1960, before Shockley and Queisser published (W. Shockley, and H. J. Queisser, J. Appl. Phys. 32, 510 (1961)) their detailed balance analysis of the efficiency of solar cells. After his analysis, the possibility of using these levels to increase the efficiency of solar cells was rejected. It is perhaps worthwhile pointing out that the possibility of using tandem solar cells, proposed by Jackson (E. D. Jackson, Trans. Conf. on the Use of Solar Energy, Tucson, 1955, University of Arizona Press, Tucson 5, 122 (1958)) was also rejected at that time since the use of tunnel junctions for connecting the cells was not yet realised. In 1997 (A. Luque, and A. Martí, Physical Review Letters 78, 5014 (1997)) researchers now in the IBPOWER consortium, used detailed balance arguments to recalculate the efficiency limit of a system with energy levels inside the bandgap assuming recombination to and from this intermediate level was radiative. They concluded that the efficiency limit of the concept was 63.2 % at maximum light concentration. This maximum was achieved for bandgaps EG=1.95 eV, EL=0.71 eV and EH=1.24 eV (see Fig 1a for notation). They also pointed out the need for an intermediate 'band' rather than a collection of intermediate 'levels' to suppress the non-radiative recombination generally introduced by energy levels located inside the gap, and the need of emitters to isolate the IB ir order to make possible the split of quasi-Fermi levels and hence the production of an output voltage (A. Luque, and A. Martí, Progress in Photovoltaics: Res. Appl. 9, 73 (2001)) not limited by EL nor EH. In order to enable the IB to accommodate electrons from the VB as well as supply electrons to the CB, the IB should be partially filled with electrons. Nevertheless, something had to be done about this intermediate level or levels to approach the radiative limit since these traditionally behave as non-radiative recombination centres that degrade the cell efficiency and must be avoided. In this respect, it was hypothesised that in order to have potential to perform radiatively, the collection of energy levels inside the bandgap, when implemented in bulk material, should constitute a 'band' (A. Luque, and A. Martí, Progress in Photovoltaics: Res. Appl. 9, 73 (2001)) and therefore the name, 'intermediate band'. Forming a 'band' versus a 'level' means that the electronic properties of the electrons in this IB should be similar to the ones they have in the conduction or valence band. If recombination radiatively limited is possible between conduction and valence band why should it not be possible between the conduction band and the valence band if in the latest the electrons have the same properties than in a conventional valence band, for example. In this respect, it was postulated that the path for inhibiting non-radiative recombination through deep centres was through the achievement of the delocalisation of the electron wavefunction when at the intermediate levels. It was postulated that this could be achieved by increasing the impurity concentration to the point where impurities became to 'see' each other (A. Luque et al., Physica B 382, 320 (2006)). Implementing the IB from deep levels acting as precursors was not the only approach proposed to take the IB approach to practice. In 2000 (A. Martí, L. Cuadra, and A. Luque, Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference, 2000, 940) it was proposed that the IB could be implemented in practice using quantum dots. When using quantum dots the IB would arise for the energy levels corresponding to the electrons confined in the dots. Quantum 'dots' and not 'wells' were preferred to implement the IBSC because, on the one hand, quantum wells do not provide a true null density of states between the IB and the conduction band but it is actually a continuum (C. Weisbuch, and B. Vinter, Quantum Semiconductor Structures, Academic Press, San Diego, 1991). On the other hand, what it would be the absorption of light from the IB to the CB is forbidden in a quantum well for front illumination (J. P. Loehr, and M. O. Manasreh, Semiconductor quantum wells and superlattices for long-wavelength infrared detectors (Artech House, Boston, 1993)). Building on these ideas IBPOWER proposed the development of IBSCs following four approaches: 1. Quantum dots. Quantum dots were actually the first experimental systems where the IB was implemented that lead to an actual solar cell (A. Luque et al., J. Appl. Phys. 96, 903 (2004)). These quantum dot systems (based on InAs/GaAs) allowed also the demonstration of some of the principles of operation of the IB concept, as for example, the absorption of two below bandgap energy photons to produce one electron-hole pair (A. Martí et al., Physical Review Letters 97, 247701 (2006)). University of Glasgow leaded this approach. 2. Thin films. It was postulated (A. Martí, D. F. Marrón, and A. Luque, J. Appl. Phys. 103, 073706 (2008)) that the insertion of Fe or Ti into CuIn1-xGaxS2 could lead to the formation of an IB at an appropriate position inside the bandgap with the potential to produce a high efficiency solar cell. IBPOWER proposed to investigate this possibility in practice. This approach, therefore, pursues the implementation of the IBSC as a low cost photovoltaic (PV) solution. Helmholtz Zentrum Berlin leaded this approach. 3. Indium Gallium Nitride with manganese (Mn). The bandgap of In1-xGaxN can potentially be tailored from <=0.77 eV (x=0) to 3.42 eV (x=1) by changing the In composition. Mn introduces a deep centre in InGaN. Because Mn can be incorporated at high dilution factors into InGaN, it was proposed (A. Martí et al., Sol. Energy Mater. Sol. Cells 93, 641 (2009)) that this deep centre could evolve into an IB when the Mn concentration would exceed the Mott transition (6 times 1019 cm-3). IBPOWER proposed to elaborate on this idea by studying this approach experimentally. University of Nottingham leaded this approach. 4. Transition metals in III-V compounds. Transition metals introduce deep centres in III-V semiconductors and, therefore, could lead to the formation of an IB if inserted at sufficiently high densities. IBPOWER proposed to study, in particular the insertion of Ti in GaAs and attempt the manufacturing of cells based on this material. Riber SA leaded this approach. The Instituto de Energia Solar of the Universidad Politécnica de Madrid coordinated the project. Project results: During its development our proposal has deployed a large effort in disseminating its results through international journals where the reader can find discussed in more detail the results we will summarise in the next paragraphs. Some of these publications will be quoted as our description of the main science and technology (S&T) results and foregrounds progresses. The operation of an IBSC relies on two main physical principles. The first is the absorption of below bandgap energy photons; the second is that the open circuit voltage of the cell is not limited by the IB. The absorption of below bandgap energy photons in quantum dot IBSCs (QD-IBSCs) was already demonstrated before this project started (A. Martí, E. Antolin, C. R. Stanley, C. D. Farmer, N. Lopez, P. Diaz, E. Canovas, P. G. Linares, and A. Luque, 'Production of Photocurrent due to Intermediate-to-Conduction-Band Transitions: A Demonstration of a Key Operating Principle of the Intermediate-Band Solar Cell,' Physical Review Letters, vol. 97, pp. 247701-4, 2006). Once the below bandgap photon absorption was demonstrated, during this proposal we have been able to demonstrate that voltage preservation also takes place in quantum dot IBSCs. First it was demonstrated using a laser source to illuminate the cells (E. Antolín, A. Martí, P. G. Linares, I. Ramiro, E. Hernández, C. D. Farmer, C. R. Stanley, and A. Luque, 'Advances in quantum dot IBSCs,' in Photovoltaic Specialists Conference (PVSC), 2010 35th IEEE, 2010, pp. 000065-000070) and a few months later using concentrated white light (P. G. Linares, A. Martí, E. Antolín, I. Ramiro, and A. Luque, 'Voltage recovery in IBSCs operated under concentration,' Solar Energy Materials and Solar cells, vol. in press, 2011). One of the main results related to this characterisation under concentrated light compares the short-circuit current versus open-circuit voltage pairs of an InAs/GaAs QD-IBSC and a GaAs reference cell. At room temperature, the open circuit voltage (VOC) of the IBSCs is lower than that of the reference cell without QDs. However, as the temperature decreases, the VOC of both cells becomes approximately the same (the VOC of the QD cell being actually higher). Then, in this way, it is shown that the open-circuit voltage of the cell is not limited by the IB created in the cell from the electron confinement in the quantum dots. The fact we have to lower the temperature to achieve this result is well explained by the IBSC theory since it is when the temperature is lowered that the thermal escape from the IB to the CB is inhibited and voltage can be recovered. When thermal escape is dominant (A. Luque, A. Marti, E. Antolin, P. G. Linares, I. Tobias, and I. Ramiro, 'Radiative thermal escape in IBSCs,' AIP Advances, vol. 1, pp. 022125-6, 2011), the quantum dots only serve to the purpose of tailoring the bandgap (which can be useful for other solar cell approaches but it is not our goal here). Voltage recovery does not occur in all QD-IBSC. QD-IBSCs fabricated to date from InGaAs/GaAs quantum dot arrays exhibit a quantum efficiency that extends to below bandgap energies. However, the production of sub-bandgap photocurrent relies often on the thermal and/or tunneling escape of carriers from the QDs, that is, without a second external photon has had necessarly to be absorbed. In E. Antolín, A. Martí, C. D. Farmer, P. G. Linares, E. Hernández, A. M. Sánchez, T. Ben, S. I. Molina, C. R. Stanley, and A. Luque, 'Reducing carrier escape in the InAs/GaAs quantum dot IBSC,' Journal of Applied Physics, vol. 108, p. 064513, 2010 we tested the effectiveness of introducing a thick GaAs spacer in addition to an InAlGaAs strain relief layer over the QDs to reduce carrier escape. From an analysis of the QE at different temperatures it was concluded that escape via tunneling can be completely blocked under short-circuit conditions, and that carriers confined in QDs with an InAlGaAs strain relief layers exhibited a thermal escape activation energy over 100 meV larger than in the case of InAs QDs capped only with GaAs. Within the context of the QD-IBSC, it is of interest to investigate the maximum value that can be achieved for the smaller of the transitions EL, since values larger than 0.3 eV are required for improved performance. In P. G. Linares, A. Martí, E. Antolín, A.Luque C.D.Farmer S.Chakrabarti C.R.Stanley A.M.Sánchez, T.Ben and S.I.Molina Energy Procedia 2, 133-141 (2010) we provided both theoretical and experimental arguments to verify the shift of the IB position to deeper energies by using an Inx(GayAl1-y)1-xAs capping layer, fulfilling the double function of increasing the QD size and eliminating the discontinuity in the conduction band between the quaternary cap and the GaAs barrier. The presence of multiple energy levels in the IBSC was studied in A. Luque, P. G. Linares, E. Antolin, E. Canovas, C. D. Farmer, C. R. Stanley, and A. Marti, Applied Physics Letters 96, 013501-3 (2010) by detailed balance calculations under ideal conditions. Since multiple levels are often found experimentally in IB cells made with quantum dots, these act to reduce the limiting efficiency determined from detailed balance calculations. Based on a generalised model of the Shockley-Read-Hall (SRH) statistics published in A. Luque, A. Martí, N. López, E. Antolín, E. Cánovas, C. R. Stanley, C. Farmer, and P. Díaz, Journal of Applied Physics 99, 094503 (2006), the effect of the partial filling of the IB in IB solar cells and the ways of producing it were analysed in A. Luque and A. Marti, Electron Devices, IEEE Transactions on 57, 1201-1207 (2010) as is its influence on the electron-hole pair generation by subband-gap photons. The differences between cells with the conduction band and the IB thermally coupled and uncoupled were stressed. The sub bandgap photon absorption of light provided by the quantum dots is insufficient to boost the cell efficiency. To solve this problem, we have proposed several strategies during the course of the project, including the investigation of growth methods that yield to increased quantum dot densities and the investigation of the impact of the shape of the quantum dots on the absorption in order to improve our understanding of the absorption processes in QDs. In A. Luque, A. Martí, E. Antolín, P. G. Linares, I. Tobías, I. Ramiro, and E. Hernandez, 'New Hamiltonian for a better understanding of the quantum dot IBSCs,' Solar Energy Materials and Solar cells, vol. 95, pp. 2095-2101, 2011 for example, we proposed a new mathematical method to calculate the wave-functions of the electrons in the QDs. This knowledge is necessary to attempt the calculation of the absorption coefficients involved in the operation of the IBSC as we did, for example in A. Luque, A. Martí, E. Antolin, and P. Garcia-Linares, 'Intraband absorption for normal illumination in quantum dot IBSCs,' Solar Energy Materials and Solar cells, vol. 94, pp. 2032-2035, 2010. In I.Tobias A. Luque, and A.Martí, Semic. Sci. Tech 26, 014031 (2011) we reported on the development of a numerical model for the IB solar cell in one dimension and studied with this model the influence doping the IB layer has on the device performance. At this stage, the IB model was simplified and included neither transport nor multiple energy levels. Two solar cell structures were simulated. Both featured a similar short circuit current increment at low concentration due to the IB; however, the open-circuit voltage and behavior under concentration were very different. In the first structure, the sub-bandgap current was large and achieved with an empty IB because the generation was completed via a strong thermal coupling of the intermediate and conduction bands; however, this implied large recombination under forward bias. Consequently the voltage was low and the current responsivity decreased steeply with concentration. In the second structure, both sub-bandgap transitions were light-induced. This leads to much better performance, although the IB must be thicker to achieve the same current as in the previous case. During the project we have also researched on technologies to assist the absorption of light by the QDs such as the use of diffraction grids and metal nanoparticles. For example: 1. In A. Mellor, I. Tobías, A. Martí, M. J. Mendes, and A. Luque, 'Upper limits to absorption enhancement in thick solar cells using diffraction gratings,' Progress in Photovoltaics: Research and Applications, vol. 19, pp. 676-687, 2011 we studied the application of diffraction gratings to solar cells to supersede the light trapping limits of conventional Lambertian structures. In this paper a mathematical formalism was derived for calculating the absorption that could be expected in a solar cell equipped with a diffraction grating, which could be applied to any lattice geometry and grating profile. Furthermore, the formalism was used to calculate the upper limit of total absorption that can theoretically be achieved using a diffraction grating. The derived formalism and limits were valid when the solar cell thickness is greater than the coherence length of the illuminating solar spectrum. Comparison was made to the upper limit achievable using an angularly selective Rugate filter, which was also calculated. Both limits were found to be considerably higher than the Lambertian limit within the range of sunlight concentration factors practically employed in photovoltaic systems (1-1000 X). The upper limit of absorption using the diffraction grating was shown to be equal to the thermodynamic limit for all absorbances and concentration factors. The limit for the Rugate filter is generally lower, but tends to the thermodynamic limit for lower cell absorbances. 2. In M. J. Mendes, A. Luque, I. Tobias, and A. Marti, 'Plasmonic light enhancement in the near-field of metallic nanospheroids for application in IBSCs,' Applied Physics Letters, vol. 95, pp. 071105-3, 2009, in order to enhance infrared light absorption in sub-bandgap transitions in an IBSC, we studied the scattered near-field potential from uncoated and coated metallic nanoparticles (Fig. 5) with a spheroidal shape using an electrostatic model. We found that the absorption enhancement produced at the surface plasmon frequency of the nanoparticles could be of several orders of magnitude in some cases. The gap of the GaAs is not the optimum for an IBSC. Higher bandgap materials should be investigated. The fundamental theory states that this bandgap should be in the range of 2 eV while the gap of GaAs is 1.42 eV. In this respect, in P. G. Linares, A. Marti, E. Antolin, and A. Luque, 'III-V compound semiconductor screening for implementing quantum dot IBSCs,' Journal of Applied Physics, vol. 109, pp. 014313-8, 2011 we searched for optimum material QD systems to implement the IBSC in the As/AlxGa1xAs, InAs1yNy /AlAsxSb1x, and InAs1zNz /AlxGayIn1y1xP families. For the search we presented an analytical method consisting of calculation of the heterojunction band alignment taking material strain into account, calculation of the QD confined energy levels constituting the IB, and calculation of the efficiency limits in the detailed balance realm and optimisation of the QD systems in terms of QD size and material composition. The optimum QD sizes were also calculated. We have also proposed new kind of quantum dot materials for the implementation of the IBSC E. Antolín, A. Martí, and A. Luque, 'The Lead Salt Quantum Dot IBSC,' Proc. 37th IEEE PVSC, 2011. One set of new materials is formed by lead salt QDs of the family IV-VI (PbTe, PbSe or PbS) embedded in a semiconductor of the family II-VI (Cd1-xMgxTe, CdxZn1-xTe, and CdS1-xSex or ZnSe1-xTex, respectively). These QDs are not nucleated due to lattice mismatch, as it is the case of the InAs/GaAs QD material system grown by the Stranski-Krastanov (S-K) mode. In these materials, the QDs precipitate due to the difference in lattice type: the QD lead salt material crystallises in the rocksalt structure, while the II-VI host material has the zincblende structure. Therefore, it is possible to use lattice-matched QD/host combinations, avoiding all the strain-related problems found in previous QD-IBSC developments. We have studied the properties of the lead salt QD materials and proposed that they are appropriate to overcome the fundamental drawbacks of present III-V based QD-IBSC prototypes. We have also calculated the band diagram for some examples of IV-VI/II-VI QD materials. Another class of quantum dots we have explored are colloidal QDs with metal nanoparticles inserted M. Mendes, A. Martí, I. Tobías, and A. Luque, 'IBSC having solution processed colloidal quantum dots,' US patent request no. 61/547,312, 2011. The quantum dots are provided with a shell which enables the absorption of photons with energies within an extended range as 10 compared to conventional solar cells, thus increasing the efficiency of the solar cell. The metal nanoparticles are efficient optical antennas at their surface plasmon resonance, attracting the light from their surroundings and focusing it in their near-field, thereby forming a light trapping structure in the cell that increases the absorption of light in the IB and, thus, further improves the conversion efficiency of the solar cell. Regarding the thin film approach, titanium has been incorporated in CuInS2 thin films and devices by diffusion of Ti from the substrate during the CuInS2 co-evaporation growth process. The CuInS2 crystal structure resulted un affected but the grain size was reduced compared to Ti-free reference samples B. Marsen, L. Steinkopf, I. Lauermann, M. Gorgoi, H. Wilhelm, T. Unold, R. Scheer, and H. W. Schock, Solar Energy Materials and solar Cells, 1730-1733 (2010) X-ray photoelectron spectroscopy showed the presence of TiO2 at the front of the absorber layer, which appeared at the heterojunction interface of the completed CuInS2/TiO2/CdS/ZnO solar cells. Low temperature photoluminescence spectra showed no additional transitions that could be assigned to Ti-based impurity defect levels. Ti-containing cells showed conversion efficiencies higher than the Ti-free reference cells due to higher open-circuit voltage (efficiency 11 %, VOC 731 mV). No reduction in short circuit current was detected indicating that the titanium did not introduce additional bulk recombination. Temperature-dependent current-voltage measurements indicated a reduced interface recombination for cells containing Ti, which is attributed to the TiO2 interlayer detected by X-ray photoelectron spectroscopy (XPS). About 0.04 per cent titanium was incorporated in CuInS2 thin films by means of a Ti-precursor layer deposited on the molybdenum back contact. The titanium did not affect the chalcopyrite crystal structure as detected by X-ray diffraction (XRD), but it did result in slightly smaller grains compared to Ti-free devices. The titanium content increased toward the front surface of the films, indicating significant diffusion of titanium within the CuInS2 lattice during the film growth. XPS measurements showed that the titanium is bonded to oxygen, establishing the presence of TiO2 in the region close to the front surface. Solar cells made from Ti-containing material showed an increase in open-circuit voltage and an increase in efficiency compared to the Ti-free devices. No significant increase in non-radiative recombination due to defects was detected. From temperature-dependent I-V measurements it was concluded that the increased open-circuit voltages resulted from a change in interface recombination due to an increased interface bandgap. In conjunction with the XPS results we concluded that the TiO2 surface layer, which in the device becomes a TiO2 interlayer between CuInS2 and CdS, was responsible for the reduced interface recombination. With the present methods of investigation, no evidence for Ti entering the chalcopyrite lattice, or for the emergence of new electronic states within the fundamental CuInS2 bandgap was found. Improvements in device performance were not due to IB action but reduction of interface recombination. The current findings suggested that the efficiency of (non-IB) Cu(In,Ga)S2-based heterojunction solar cells could be improved by the use of suitable functional layers at the heterojunction interface. Other synthesis methods (co-evaporation of impurity species) and material systems (CuGaS2) were suggested as avenues toward bulk IB materials. In order to progress towards thin film semiconductor hosts with larger bandgaps, the incorporation of metal impurities M (M=Ti, Fe, or Sn) into CuGaS2 films was investigated experimentally as a function of impurity concentration (B. Marsen, S. Klemz, G. Landi, L. Steinkopf, R. Scheer, S. Schorr, and H. W. Schock, Thin Solid Films (2011)). Films were synthesised by thermal co-evaporation of the elements onto glass/Mo substrates heated from 400 °C to 570 °C. The compositions of the resulting films were measured by energy-dispersive X-ray spectroscopy and the structures of the present phases are studied by X-ray diffraction. The formation of Cu-M-S ternary phases was observed in a wide range of conditions. Films of Cu-Ga-Ti-S, synthesised at 500 °C, showed the presence of a cubic modification of CuGaS2 and Cu4TiS4. Alloying of CuGaS2 and tetragonal Cu2SnS3 was observed for substrate temperatures of 450 °C. A miscibility gap opens at 500 °C and above with separate Sn-rich and Ga-rich phases. Similarly, alloys of CuFeS2 and CuGaS2 were only found in Cu-Ga-Fe-S films synthesised at lower substrate temperature (400 °C), whereas at 500 °C a miscibility gap opened leading to separate Fe-rich and Ga-rich phases. Photovoltaic devices were fabricated from CuGa1-xFexS2 thin films concurrently deposited on Mo-coated glass substrates using the standard chalcopyrite glass/Mo/absorber/CdS/ZnO device structure. The device characteristics of these solar cells were evaluated by current-voltage and quantum efficiency measurements. For Fe-containing CuGaS2 films, distinct sub-gap absorption bands at 1.2 eV and 1.9 eV were detected, which increased in prominence with increasing Fe content. On the other hand, the solar cell parameters were found to deteriorate with increasing iron content, indicating an increase in non-radiative recombination when high levels of iron are incorporated. However, for the lowest iron content (x=0.003) an increase in the sub-gap photoresponse at about 1.9 eV was observed, which is attributed to a combination of sufficient IB absorption and carrier collection at this dilution level (B. Marsen, S. Klemz, T. Unold, and H.W. Schock, Progress in Photovoltaics: Research and Applications, n/a-n/a (2012)). The electronic structure of modified CuGaS2 was also analysed from first principles within the density functional theory. The chalcopyrite matrix was modified by introducing a high concentration of atomic impurities that included transition metals and elements of group IVa at substitutional sites of the lattice host. For selected cases, an IB was theoretically predicted that potentially fulfils the requirements as stated for intermediate-band solar cell materials. Preliminary thermochemical estimations of the stability of the compounds proposed against eventual secondary phases in the form of binary chalcogenides greatly simplified the general screening. Elements of groups VIIIb and IVa were identified as interesting impurity candidates to obtain IBs within the main gap of the modified ternary host. Additionally, modified chalcopyrite compounds with potential applications as magnetic semiconductors or spintronic materials were identified. The transformation of chalcopyrite compounds as used for thin-film solar cells into intermediate-band materials could have a particular impact on the design of thin-film intermediate-band solar cells, with improved figures of energy conversion efficiency expected (C. Tablero and D. Fuertes Marrón, The Journal of Physical Chemistry C 114, 2756-2763 (2010)). In progress towards a next generation of photovoltaics, devices based on InGaN may play a significant role, due to the unique properties of the nitride-based materials. In particular, because the band gap covers the entire range from 0.64 eV for InN to 3.4 eV for GaN, devices based on InGaN are now being extensively studied for various applications. InGaN-based opto-electronic devices already form the basis for industrial applications including, blue light emitting diodes (LEDs) and blue/violet laser diodes and for electronic devices including high-power RF transistors. The same material system will form the basis for future solid state lighting, by combining efficient nitride based LEDs with appropriate phosphors to obtain the correct colour balance. In many cases, a key issue is the quality and availability of suitable substrates, since unlike other III-V compounds, no bulk substrates are available for group III-Nitride semiconductors. For photovoltaic applications, the ability to cover the whole of the spectral range in a single materials system could have significant implications for cost savings; however, there is a considerable mis-match in lattice parameter between InN and GaN, which would make conventional multi-junction solar cells difficult to produce without introducing a high defect density. In our project we have investigated an alternative approach to high-efficiency solar cells as it is the IBSC (IBSC). In C. T. Foxon, S. V. Novikov, and R. P. Campion, in Next Generation of Photovoltaics: New Concepts edited by A.B.Cristóbal, A.Martí, and A.Luque (Springer Verlag, Berlin, 2012) we discussed the growth method needed to produce suitable InGaN-based structures, in particular the use of Mn in InGaN to form the IB within an InGaN p-i -n heterojunction. It is also well known, however, that there are significant difficulties associated with p-doping for In-rich InGaN, which were also discussed. In our project we have collaborated also with University of Cadiz (F. M. Morales, D. Carvalho, T. Ben, R. García, S. I. Molina, A. Martí, A. Luque, C. R. Staddon, R. P. Campion, and C. T. Foxon, Scripta Materialia 66, 351-354 (2011)) to study the morphology of our InGaN grown by MBE (J. L. Hall, A. J. Kent, C. T. Foxon, and R. P. Campion, Journal of Crystal Growth 312, 2083-2088 (2010)) in which special attention was devoted to the control of the temperature during growth. In this respect, temperature rises during growth of nxGa1-xN on non-mounted GaAs substrates were observed. The magnitude of the rise was found to increase with increasing in content. A semi-quantitative model has been presented, which despite its limitations we believe explains the origin of the rises observed during the growth of GaN and InN on GaAs. The small rise in GaN is a result of a phonon frequency difference between GaAs and GaN, while the large rise in InN is due to large numbers of free carriers present in the InN layer. The lack of a heat loss mechanism in the model currently means that it cannot yet be used for other growth scenarios. Model results were only presented for GaN and InN, as too many unknowns exist for InxGa1-xN.The rises in temperature largely occur as only a small percentage of the heater radiation is coupled into the substrate prior to growth. Different system configurations are therefore expected to yield different results, for example, substrates mounted on PBN plates should lead to much smaller temperature rises. Concerning the implementation of the IBSC on GaAs using transition metals, it is expected that the main results appear published in some journal in the next months. However, at the moment of writing these lines and given that this document is public domain, we cannot unclose yet the results. Potential impact: The research this project has undertaken is of fundamental type and therefore, its real socio-economic impact is foreseen in the long term. Related to long term targets, the IB concept pursues, by producing high efficiency solar cells at low cost, to impact in the achievement of the goals identified by the European photovoltaic technology platform for 2020 (0.1 per kWh for the typical electricity generation costs in Southern Europe; 1.5 per Wp for the typical turn-key price for a 100 kW; 0.5 years for the typical system energy payback time in southern Europe) in their roadmap to achieve the Strategic Energy Technology (SET) plan objectives to reduce carbon dioxide (CO2) emissions by 20 % by 2020, increase to 20 % by 2020 the renewable energy share of the energy mix and improve energy efficiency by 20 % by 2020. At scientific level, the scheme followed in the project to research on IBSCs is expected to impact the research with which other groups could develop the idea. Our scheme encourages accelerating the research at device level as the approach to achieve the general picture about whether a particular IBSC implementation is going to work as well as to early identify its weaknesses. For example, it might happen that very efficient IB materials are identified in the future but, although without doubt interesting from a fundamental point of view, they might become will be useless to produce efficient solar cells if we do not develop in parallel the technology for properly contacting them without losses. If these materials are too exotic, it might be that the technology for contacting them also requires substantial research effort. This is why we encourage research at complete device level. It has been motivating that other Groups worldwide have independently developed proof of concept IBSC devices based on different materials. Some examples worldwide are ZnTe:O solar cells (W. Wang, A. S. Lin, and J. D. Phillips, Applied Physics Letters 95, 011103, 2009) and GaNxAs1-x alloys (N. Lopez, L. A. Reichertz, K. M. Yu, K. Campman, and W. Walukiewicz, Physical Review Letters, vol. 106, p. 028701, 2010). The number of IB material candidates increases yearly. Not all of them will work, but this fact emphasises our idea of attempting their practical implementation as early as possible in order to learn if this is the case. The project has done a large dissemination effort mainly through international peer reviewed journals. We hope this effort is useful to other researchers, not only to learn from the things we might have done right but, most importantly, from our mistakes. The following is a selected list of publications that reflect IBPOWER's work: 1. E. Antolín, A. Martí, C. Farmer, P. G. García- Linares, E. Hernández, A. M. Sánchez, T. ben, S. I. Molina, C. Stanley, and A. Luque, 'Reducing carrier scape in the InAs/GaAs quantum dot IBSC,' Journal Applied Physics, vol. 108, p. 064513 2010 2. E. Cánovas, D. F. Marron, A. Martí, A. Luque, A. Bett, F. Dimroth, and S. Phillips, 'Photoreflectance analysis of a GaInP/GaInAs/Ge multijunction solar cell,' Appl. Phys. Lett., vol. 97, p. 203504, 2010 3. E. Canovas, A. Marti, A. Luque, and W. Walukiewicz, 'Optimum nitride concentration in multiband III-N-V alloys for high efficiency ideal solar cells,' Applied Physics Letters, vol. 93, p. 174109, Oct 27 2008 4. P. G. García- Linares and e. al., 'Inx(GayAl1-y)1-xAs quaternary alloys for quantum dot IBSCs,' Energy Procedia, vol. 2, pp. 133-141, 2010 5. J. L. Hall, A. J. Kent, C. T. Foxon, and R. P. Campion, 'Temperature effects during the growth of InxGa1-xN films through the whole compositional range by plasma-assisted molecular beam epitaxy,' Journal of Crystal Growth, vol. 312, pp. 2083-2088, Jul 2010 6. P. G. Linares, A. Martí, E. Antolin, and A. Luque, 'III-V compound semiconductor screening for implementing quantum dot IBSCs,' Journal Applied Physics, vol. 109, p. 014313, 2011 7. F. LLopis, I. Tobias, and M. Jakas, 'Light intensity enhancement inside the grooves of metallic gratings,' J. Opt. Soc. Am. B, vol. 27, p. 129233, 2010 8. A. Luque, P. García-Linares, E. Antolin, E. Cánovas, C. Farmer, C. Stanley, and A. Martí, 'Multiple levels in IBSCs,' Appl. Phys. Lett., vol. 96, pp. 013501-3, 2010 9. A. Luque and A. Marti, 'Can impurities be beneficial to photovoltaics?,' Solid State Phenomena, vol. 156-158, pp. 107-114, 2010 10. A. Luque and A. Martí, 'On the Partial Filling of the IB in IB Solar Cells,' IEEE Transactions on Electron Devices, vol. 57, pp. 1201-1207, 2010 11. A. Luque and A. Martí, 'Photovoltaics: Towards the IB,' Nature Photonics, vol. 5, pp. 137-138, 2011 12. A. Luque, A. Martí, E. Antolín, and P. G. García- Linares, 'Intraband Absorption for Normal Illumination in Quantum Dot IBSCs,' Solar Energy Materials and Solar Cells, vol., 2010 13. A. Luque, A. Marti, E. Antolín, P. García-Linares, I. Tobías, and I. Ramiro, 'Radiative thermal escape in IBSCs,' AIP Advances, vol. 1, pp. 022125-6, 2011 14. A. Luque, A. Martí, E. Antolín, P. García-Linares, I. Tobías, I. Ramiro, and E. Hernandez, 'New Hamiltonian for a better understanding of the quantum dot IBSCs,' Solar Energy Materials and Solar Cells, vol. 95, pp. 2095-2101, 2011 15. B. Marsen, S. Klemz, G. Landi, L. Steinkopf, R. Scheer, S. Schorr, and H. W. Schock, 'Evaluation of Impurity- Modified CuGaS2 as Thin Film Intermediate Band Absorber Materisl,' Thin Solid Films, vol. 2010 16. B. Marsen, S. Klemz, G. Landi, L. Steinkopf, R. Scheer, S. Schorr, and H. W. Schock, 'Phases in Copper-Gallium-Metal-Sulfide Films (Metal=Titanium, Iron, or Tin),' Thin Solid Films, vol. 519, pp. 7284-7287, 2011 17. B. Marsen, S. Klemz, T. Unold, and H. W. Schock, 'Investigation of the Sub-Bandgap Photoresponse in CuGaS2:Fe for IBSCs,' Progress in Photovoltaics: Research and Applications, 2011 18. B. Marsen, L. Steinkopf, A. Singh, H. Wilhelm, I. Lauermann, T. Unold, R. Scheer, and H. W. Schock, 'Effects of Ti- incorporation in CuInS2,' Solar Energy Materials and Solar Cells, vol. 94, pp. 1730-1733, 2010 19. B. Marsen, H. Wilhelm, L. Steinkopf, S. Klemz, T. Unold, R. Scheer, and H. W. Schock, 'Effect of copper-deficiency on multi-stage co-evaporated Cu(In,Ga)S2 absorber layers and solar cells,' Thin Solid Films, vol. 519, pp. 7224-7227 2011 20. A. Martí, C. Tablero, E. Antolín, R. P. Campion, S. V. Novikov, and C. T. Foxon, 'Potential of Mn doped In1-xGaxN for implementing IBSCs,' Solar Energy Materials and Solar Cells, vol. 93, pp. 641-644, 2009 21. A. Mellor, I. Tobias, A. Marti, and A. Luque, 'A numerical study of Bi- periodic binary diffraction granting for solar cells,' Solar Energy Materials and Solar Cells, vol. 95, pp. 3527-3535, 2011 22. A. Mellor, I. Tobías, A. Martí, M. J. Mendes, and A. Luque, 'Upper limits to absorption enhancement in thick solar cells using diffraction gratings,' Progress in Photovoltaics, vol. 18, pp. 1-12, 2011 23. M. J. Mendes, A. Luque, I. Tobias, and A. Marti, 'Plasmonic light enhancement in the near-field of metallic nanospheroids for application in IBSCs,' Applied Physics Letters, vol. 95, p. 3, Aug 2009 24. M. J. Mendes, I. Tobias, A. Marti, and A. Luque, 'Light concentration in the near-field of dielectric speroidal particles with mesoscopic sises,' Optics Express, vol. 19, pp. 16207-16222, 2011 25. M. J. Mendes, I. Tobias, A. Martí, and A. Luque, 'Near-field scattering by dielectric spheroidal particles with sises on the order of the illuminating wavelength,' Journal of the Optical Society of America B-Optical Physics, vol. 27, pp. 1221-1231, 2010 26. I. Ramiro, E. Antolin, P. G. Linares, E. Hernández, A. Martí, A. Luque, C. D. Farmer, and C. Stanley, 'Application of photoluminescence and electroluminescence techniques to the characterisation of IBSCs,' Energy Procedia, vol. 10, pp. 117-121, 2011 27. C. Tablero, 'Representations of the occupation number matrix on the LDA/GGA+U method,' Journal of Physics: Condensed Matter, vol. 20, p. 325205, 2008 28. C. Tablero, 'Effects of the orbital self-interaction in both strongly and weakly correlated systems ' Journal of chemical Physics, vol. 130, p. 054903, 2009 29. C. Tablero, 'Effects of the impurity-impurity and impurity-host interactions on the charge density and the related processes,' Physica B-Condensed Matter, pp. 4023-4028, 2009 30. C. Tablero, 'Quantum dot energy levels and spectrum for different geometries,' Journal Applied Physics, p. 074306, 2009 31. C. Tablero, 'Ionisation levels of doped sulfur and selenium chalcopyrites,' Journal Applied Physics, p. 073718, 2009 32. C. Tablero, 'Static and dynamic ionisation levels of transition metal-doped zinc chalogenides,' Theoretical Chemistry Accounts pp. 23-24, 2010 33. C. Tablero, 'Acceptor and donor ionisation energy levels in O-doped ZnTe,' Computational Materials Science, vol. 49, pp. 368-371, 2010 34. C. Tablero, 'Electronic and magnetic properties of the Fe doped CuInS2,' Chem. Phys. Lett, vol. 499, pp. 75-78, 2010 35. C. Tablero, 'Effects of the impurity-host interactions on the non-radiative processes in ZnS:Cr,' Journal Applied Physics, vol. 108, p. 093114, 2010 36. C. Tablero, 'Electronic and optical properties of the group IV doped copper gallium chalcopyrites,' Thin Solid Films, vol. 19, pp. 1435-1440, 2010 37. C. Tablero and D. F. Marron, 'Analysis of the electronic structure of modified CuGaS2 with selected substitutional impurities: prospects for IB thin film solar cells based on Cu-containing chalcopyrites,' Journal of Physical Chemistry C, vol. 114, pp. 2756-2763, 2010 38. C. Tablero, A. Martí, and A. Luque, 'Ionisation Energy levels in Mn-doped InxGa(1-x) alloys,' Journal of Applied Physics, vol. 105, pp. 033704-4, 2009 39. C. Tablero, A. Martí, and A. Luque, 'Analyses of the intermediate energy levels in ZnTe:O alloys,' Applied Physics Letters, vol. 96, p. 3, 2010 40. I. Tobias, A. Luque, and A. Marti, 'Numerical modelling of IBSCs,' Semic. Sci. Tech., vol. 26, p. 014031, 2011. In addition to the publication in journals referred to in the previous section, the project has disseminated its results in several international conferences. First results were communicated in 2008 at the 23rd European Photovoltaic Solar Energy Conference, Valencia (Spain) where we presented the optical characterisation of the first quantum dot IBSCs grown within the project. The cells were developed by growing a stack of ten InAs/GaAs QDs layers between p and n doped GaAs conventional emitters. Electroluminescence (EL) photoreflectance (PR) and transmission electron microscopy (TEM) were applied to the samples in order to test and characterize them optically. The results, derived from the application of the different techniques, showed a good correlation. TEM images revealed a very good structural quality of the QDs, which seemed to evolve in shape-strain from the bottom to the top of the stack. Corresponding to the quality observed by TEM, strong signals from EL and PR resolved unambiguously the energy band diagram of the QDIBSCs. By fitting PR data we were able to identify the coexistence of bands and discrete energy levels coming from the IB material. The PR data evidenced also a strong electric field over the dots, attributed to the space charge region created between the p-n emitters sandwiching the IB material. From EL results, we identified the predominantly radiative nature of the IB material related energy transitions. We also published the first studies on the theoretical analysis of thin Film IB chalcopyrite solar cells performance and prospects for their realisation that we exhibited during the 23rd European Photovoltaic Solar Energy Conference held in Valencia (Spain). Compounds belonging to the group of I-III-VI2 chalcopyrites, used as absorbers in the leading thin-film technology, appeared as promising candidates for the realisation of IB-devices. In this work we first analysed the expected performance of such a thin-film IBSC (TF-IBSC) by considering different levels of idealisation, and secondly we discussed some issues relevant for the practical realisation of IBs in chalcopyrites and identified impurities acting as potential IB-precursors in the chalcopyrite sulphide host. In the same conference, a study of recombination properties of IBSCs, expected to be different from those traditionally attributed to deep levels, was shown by exploiting computational models based on ab-initio calculations. We also disseminated our results at the European Material Research Conference, one of the largest conferences on materials worldwide; and in the 3rd International Workshop on Modulation Spectroscopy of Semiconductor Structures presenting studies about thin film IBSCs. In 2009 we attended the IEEE Photovoltaic Specialists Conference. The IEEE PVSEC Conference registers around 1000 contributions in each conference. Here and with an oral contribution we disseminated the objectives of the project and the work that we have been done within this European research proposal. A similar work describing the impact of our research consortium was presented at the European Photovoltaic Conference (24th edition). In 2010 we presented our results on the advances in quantum dot IBSCs during the 35th IEEE Photovoltaic Specialists Conference, Honolulu, Hawaii (EEUU). In that work, we discussed the contribution of thermal and tunnelling mechanisms to IB-CB carrier escape in current QD-IBSCs. It is experimentally demonstrated that in QDIBSC prototypes where tunnel escape has been eliminated, the sub-bandgap QE is suppressed at sufficiently low temperatures, and when this occurs, the only limit for the open-circuit voltage (VOC) is the fundamental semiconductor bandgap, as stated by the IBSC theoretical model. That year we also discussed how we could raise the efficiency limit of the GaAs-based IBSC through the implementation of a monolithic tandem with an AlGaAs top cell at the 5th World Conference on Photovoltaic Energy Conversion, Valencia, Spain. We proposed the implementation of a multi-junction device consisting of an IBSC combined with a single gap cell. We calculate the efficiency limits using the detailed balance model and conclude that they are very high (higher than 60 % under maximum concentration) for any fundamental bandgap from 0.7 to 3.6 eV in the IBSC inserted in the tandem. In particular, the two-terminal tandem of a GaAs-based IBSC current matched to an optimised AlGaAs top cell has an efficiency limit as high as 64 %. We also presented the modelling and characterisation of multiple level IBSC. In the framework of the project we had manufactured InAs/GaAs QD-IBSCs in order to test the validity of the IBSC concept, although their real size and shape were far from the optimum and this caused extra electron levels to appear within the nanostructure confining potential, degrading the performance of the device. The effect of these extra levels were studied through a multiple level IBSC model based on the detailed balance, but modified so a term accounting for the non-radiative recombination (NRR) is also included. The model was completed with constant fitting parameters so the concentration JL-VOC curves (which do not incorporate series resistance effects) can be fitted. Several QD-IBSCs were manufactured, measured and fitted with this model, rendering relevant information about the recombination nature of the QD-IBSCs. In the field of characterisation and at the same conference the results of the optoelectronic characterisation of IBSCs by photoreflectance comparison to other advanced architectures were introduced. We knew that the fabrication and design of novel materials and devices for advanced photovoltaics, like the intermediate-band solar cell (IBSC), required the use of specific characterisation tools providing information about their optoelectronic properties. So we tested the suitability of photoreflectance for the characterisation of IBSC prototypes based on quantum dots and compared the results obtained with those predicted by the theory. Non idealities in operative devices were identified and detailed information obtained about the electronic structure of the materials. We demonstrated the potential of the technique. Within the strategy of increasing the absorption of quantum dots, as mentioned, the project has also considered the option of light trapping in the near and far field. Works regarding both options were exhibited at this conference. We explored an experimental procedure to embed MNPs in gallium arsenide (GaAs) and silicon (Si), which can be applied to other semiconductor host materials. The approach consisted in spin-coating colloidal MNPs dispersed in solution onto the substrate surface. Then a capping layer of the same material as the substrate is deposited on top to embed the MNPs in the semiconductor. The extinction spectra of silver (Ag) and gold (Au) MNPs embedded in GaAs and Si is modeled with Mie theory for comparison with optical measurements. This contribution constituted the initial step towards the realisation of quantum-dot IBSCs (QD-IBSC) with MNPs. On the other hand computational calculations of light trapping properties of cylindrical well diffraction gratings in solar cells (far field) were also presented conclusing that a field intensity enhancement of the order of 100 is achievable. Finally, in a plenary talk at the European PV Conference, the experimental advances in the next generation of solar cells were exposed comparing the experimental results obtained for three most reliable concepts for exceeding 50 % efficiency: the multiple exciton generation (or impact ionisation or multiple carrier generation) solar cell, the IBSC and the hot carrier solar cell. These concepts were proposed theoretically more than ten years ago. In the last years, the number of experiments supporting the theories behind and paving the way towards their practical implementation has leaped forward. We reviewed these experimental advances. It is worth highlighting that the impact of all results presented in this exhibition and congress were extremely high as that year the conference joined the 25th European Photovoltaic Solar Energy Conference and Exhibition, the 36th US IEEE Photovoltaic Specialists Conference and the 20th Asia/Pacific PV Science and Engineering Conference. On the other hand at that time prototypes based on InAs/GaAs QDs had been also manufactured in order to realize the theoretically predicted high efficiency IBSCs (IBSCs). We analysed the absorption coefficient of the IB material by developing a sample in an optical wave-guided configuration. This configuration allowed us to illuminate the QDs laterally, increasing the path length for photon absorption. Using a multi-section metal contact device design, we were able to measure an absorption coefficient of similar to 100cm(-1) around the band edge (similar to 1eV) defined by the VB to IB transition in InAs/GaAs QD-IB materials. These results were shown at the European Material Research Society Conference, a five days conference with 25 sessions running in parallel. At the same conference the potential of In-x(GayAl1-y)(1-x)As quaternary alloys for quantum dot IBSCs was proposed. Within the context of quantum dot IBSCs (QD-IBSC), it is of interest to investigate the maximum value that can be achieved for the smaller of the transitions (E-L), since values larger than 0.3 eV are required for improved performance. Our work provided both theoretical and experimental arguments to verify the shift of the IB position to deeper energies by using an In-x(GayAl1-y)(1-x)As capping layer, fulfilling the double function of increasing the QD size and eliminating the discontinuity in the conduction band between the quaternary cap and the GaAs barrier. In 2011 we participated again at the IEEE Photovoltaic Specialists Conference (37Th Edition) due to the relevance and impact of this conference. We proposed a new kind of quantum dot (QD) materials for the implementation of the IBSC (IBSC). The materials were formed by lead salt QDs of the family IV-VI (PbTe, PbSe or PbS) embedded in a semiconductor of the family II-VI (Cd1-xMgxTe, CdxZn1-xTe, and CdS1-xSex or ZnSe1-xTex, respectively). These QDs are not nucleated due to lattice mismatch, as it is the case of the InAs/GaAs QD material system grown by the Stranski-Krastanov (S-K) mode. In these materials, the QDs precipitate due to the difference in lattice type: the QD lead salt material crystallises in the rocksalt structure, while the II-VI host material has the zincblende structure. Therefore, it is possible to use lattice-matched QD/host combinations, avoiding all the strain-related problems found in previous QD-IBSC developments. We discussed the properties of the lead salt QD materials and proposed that they are appropriate to overcome the fundamental drawbacks of present III-Vbased QD-IBSC prototypes. We also calculated the band diagram for some examples of IV-VI/II-VI QD materials. Our advances on light trapping strategies were introduced in the Optical Society American meeting on Photovoltaic, in the Electromagnetics Research Symposium held in Marrakesh and in the 8th Spanish Conference on Electron Devices. In the first one we explored the near-field concentration properties of dielectric spheroidal scatterers with sises close to the wavelength, using an analytical separation-of-variables method (Mendes, M. J., I. Tobías, et al. (2011), 'Near-field light focusing by wavelength-sised dielectric spheroids for photovoltaic applications', OSA meeting on Photovoltaics. Austin, TX, 2 to 4 November). In the second one we explaining the possibility of using the rectangular-shaped grooves of a perfectly conducting diffraction grating as a light-trapping structure for producing light-confinnement in photovoltaic and optoelectronic devices (Jakas, M. M., F. Llopies, et al. (2011). Light Trapping within the Grooves of Diffraction Gratings. Progress In Electromagnetics Research Symposium Proceedings, Marrakesh, Morocco). And in the last one we evaluated the potential improvements derived from the absorption increase employing a simplified model to analyze the low-injection behaviour of a solar cell with a metallic grating backreflector (Llopis, F., M. M. Jakas, et al. (2011). Low-injection behaviour of a solar cell with a metallic grating back-reflector. 8th Spanish Conference on Electron Devices, CDE'2011, Palma de Mallorca, Spain). Finally we participated in the 2011 edition of the European Material Research Society Congress, where we explained that luminescence spectra render valuable information for the analysis of IBSCs, as they reveal the dynamics of carrier relaxation between the different bands. In that work the temperature dependence of the PL and EL spectra of two InAs/GaAs QD-IBSCs was studied. The EL spectra at room temperature were not in agreement with the IBSC model and they can be explained by a too fast carrier relaxation between CB and IB. However, at low temperatures that relaxation was slowed down and the results were consistent with a QFL split between those two bands as predicted by the IBSC model. PL spectra appeared to be less useful for this kind of analysis than EL spectra since the luminescence of the emitter of the cell cannot be distinguished from that of the IB material (Ramiro, I., E. Antolín, et al. (2011), Application of photoluminiscence and electroluminiscence techniques to the characterisation of IBSCs, European Materials Research Society Conference, (EMRS), Symposium of Advanced Inorganic Materials and concepts for photovoltaics, Nice). An important effort has also been done to disseminate our knowledge in a more comprehensive and detailed way through the following chapters of books: 1. C. T. Foxon, S. V. Novikov, and R. P. Campion, in Next Generation of Photovoltaics: New Concepts, edited by A. B. Cristobal, A. Marti, and A. Luque (Springer Verlag., 2012), pp. 277 2. P. G. Linares, in Advanced Solar Cell Materials, Technology, Modeling, and Simulation, edited by R. a. M. Y. T. T. I. Laurentiu Fara (Polytechnic University of Bucharest, Japan) (IGI Global Dissemination of Knowledge, 2012) 3. A. Martí, and A. Luque, in Next Generation of Photovoltaics: New Concepts, edited by A. B. Cristobal, A. Marti, and A. Luque (Springer Verlag., 2012), pp. 209 4. Stanley et al., in Next Generation of Photovoltaics: New Concepts, edited by A. B. Cristobal, A. Marti, and A. Luque (Springer Verlag., 2012), pp. 251 5. E. Antolín, A. Martí, A. Luque, 'The IBSC' in Comprehensive Renewable Energies, Eds. Ali Sayigh, Elsevier. We also would like to mention that the project have been also working for increasing the awareness of researchers of cross-cutting areas, policy makers and general public by giving explanatory talks on renewable energies, photovoltaics and novel concepts. For example: 1. Display stand at University of Glasgow Industry Days (2010) 2. Invited talk From Semiconductor to New Energy - the PV Value added Chain, European - American Energy Conference 2011, Nice 3. Invited talk: Photovoltaics: Large Scale Power-Providing Semiconductor Industry, 2011 4. Invited talk: Nanostructured and bulk materials in IBSCs. MRS Spring Meeting 5. Invited talk: Progress in IBSCs. Bayer innovative. Schloss Erlangen, Alemania, 2011 6. Invited talk: IBSCs. OECC 2009. Hong-Kong, 2009 7. Invited presentation at 1st Annual SU2P Symposium, University of Strathclyde. 2010 8. Presentation to Sasol Technology (UK), St Andrews, Scotland 2010 9. Invited talk 'Examples of partcipation in FP7, IBPOWER' at CDTI, Spain, 2009 10. Invited presentation at 'Third Generation Photovoltaics' Workshop, Heriot-Watt University, Edinburgh 2010 11. Talk 'The IBSC: theory and praxis'at the workshop NANOfutures: A cross-ETP Coordination Initiative on nanotechnology, 2011 12. Invited talk in PV Trends 2008 Bucharest, 2008 13. Invited talk 'Empirical methods in quantum dot IBSC research' at the Workshop on Empiral methods on Solid StatePhysics, Manchester, 2010 14. Invited talk 'On the temperature rise model for InGaN on GaAs' at ETSI Telecomunicación, Universidad Politécnica de Madrid, 2009 15. Invited talk 'On the temperature rise model for InGaN on GaAs' at UK Nitride Consortium Conference at Sheffield University, 2009 16. Talk 'Chalcopyrite-based nanostructures: new prospects for highly efficient photovoltaic devices' in Trends in NanoApplications - Energy. Imaginenano 2011, Bilbao, 2011 17. Invited Seminar at the University of Cambridge (Department of Physics, 2010 18. Talk 'The AME technique' at the UK Nitride consortium meeting at the University of Bath, 2011 19. Presentation 'Growth of III nitrides using the AME process' at the International Nitrides (ICNS9) conference, Glasgow, 2011 20. Talk 'The AME technique' at the UK MBE Workshop Sheffield (UK), 2011 21. Invited talk 'Advances in IB Cell Research' at the Nature Photonics Technology ConferenceTokio, Japan, 2010 22. Invited talk 'Nanotechnology for more efficient photovoltaics: the quantum dot IBSC' at CASP 2011 Annual Meeting Los Alamos National Laboratory, Nuevo Mejico, EEUU, 2011 23. Invited talk 'IBSC' at Rusnano Forum: IV Nanotechnology International ForumRussia, 2011 24. Classes at the School on Nanotechnology and New Materials for Environmental Challenges (First Bilateral Japan-Spain Meeting on Nanotechnology and New Materials for Environmental Challenges) Toledo, Spain, 2011 25. Invited talk ImagineNano 2011 'Nanotechnology for more efficient photovoltaics: the quantum dot IBSC - Bringing together Nanoscience and Nanotechnology, Bilbao, 2011 26. Invited talk 'Novel Photovoltaic Devices: the IBSC' at NANOMAT 2008, Ankara, Turkey, 2008 27. Invited talk 'IBSCs' to 17th International Conference on Photochemical Conversion and Storage of Solar Energy Conference Sydney, Australia, 2008 28. Invited talk 'Energía Solar Fotovoltica' by Telefónica S.A. Madrid, Spain, 2008 29. Invited talk by Workshop 'Progress Towards a Next Generation in Photovoltaics, Cercedilla, 2008 30. Invited talk 'Células de 3ª generación. Novel Concepts in Photovoltaics' at two Cumbre de Concentración Fotovoltaica Toledo, España, 2009 31. Invited talk 'A quick guide to IBSC research' at the heriot Watt University 2010 32. Invited Talk 'IBSCs' at CIMTEC 2010, 2010 33. Invited talk 'Intermediate-band gap solar cells' at the 24th Nordic Semiconductor MeetingFuglsøcentret, Denmark, 2011. Some other activities as tours, news and press-releases related to the IBSC have been also generated: 1. Photon Internacional 'IB cells are on their way' February 2012 2. NCPV Hotline 'Intermediate-band solar cells' February 2012 3. La Vanguardia. 'Reserachers of the UPM invents the IBSC' February 2012 4. Energías Renovables 'The IBSC conquists Nature Photonics' February 2012 5. GENERA Renoweble Energy Fair. B2B meetings 2010 6. Madrid Week of Science 'Photovoltaics', 2009, 2010 and 2012, guided visits to IBLAB, the IBSC Laboratory. List of websites: The website of the project is located at http://www.ies.upm.es/ibpower The partners in IBPOWER , with their corresponding contact details are: 1. The Instituto de Energía Solar of the Universidad Politécnica de Madrid, that coordinates the project (see http://www.ies.upm.es online). Contact persons are Profs. Antonio Martí (amarti@etsit.upm.es via e-mal) and Antonio Luque (a.luque@upm.es via e-mail) 2. The University of Glasgow, that implements the technology based on quantum dots (see http://www.gla.ac.uk/departments/electronicsandelectricalengineering/ online). Contact person is Prof. C. R. Stanley (c.Stanley@elec.gla.ac.uk via e-mail). 3. The Helmholtz Zentrum Berlin (see http://www.helmholtz-berlin.de online) that implements the technology based on the thin film approach. Contact persons are Prof. H. W. Schock (hans-werner.schock@helmholtz-berlin.de via e-mail) and Dr Thomas Unold (unold@helmholtz-berlin.de via e-mail) 4. The University of Nottingham (see http://www.nottingham.ac.uk online) that implements the technology based on InGaN. Contact persons are Profs. C.T.Foxon (C.Thomas.Foxon@nottingham.ac.uk via e-mail) and R. Campion (Richard.Campion@nottingham.ac.uk via e-mail) 5. Riber SA (see http://www.riber.com e-mail) that implements the technology dealing with the implementation of transition elements on III-V compounds. Contact person is Dr C. Chaix (cchaix@riber.fr via e-mail). Documents connexes Final Report - IBPOWER (Intermediate band materials and solar cells for photovoltaics with high efficiency and reduced cost)
