Final Report Summary - PRIMA-ERA (Promoting and Improving Azerbaijan Research Collaboration with European Research Area)
Executive Summary:
Main goal of the PRIMA-ERA project is reinforce research collaboration between the Institute of Physics, Azerbaijan National Academy of Sciences (IPA) and research centres in the European Research Area. The IPA is a leading organization on scientific research, knowledge transfer and graduate education in physics in Azerbaijan. PRIMA-ERA will facilitate the collaboration of the IPA with research centres in EU member and associate countries and reinforce its engagement in the FP7 projects in research topics covered by such thematic priorities as energy and nanotechnologies.
The primary objectives of the project are:
- to increase IPA capacities and preparedness for collaboration in the FP7 through twinning and networking, development of joint research plans and training modules and trainings;
- to increase visibility of IPA for international scientific community and other stakeholders through dissemination of scientific information and promotional activities;
- to ensure the compliance of the IPA’s research activities with socio-economic needs of the country and regionally and provide better career opportunities for young scientists through encouragement innovative approaches and development of research strategy.
The project consortium between the IPA, CNRS Institut de Recherche et Development sur l’Energie Photovoltaique, CNRS-IRDEP (France) and TUBITAK – Marmara Research Centre, TUBITAK - MAM (Turkey), has been established to effectively fulfill the project’s objectives.
The PRIMA-ERA complies with the EU strategies for an “open ERA” as mentioned in the EC Communication for International S&T Cooperation by providing mobility and access to research facilities between the centres with similar research interests. The project actions are in coherence with the concept of the “mutual interests of the EC and the ENP partner countries” as stated in the mentioned Communication.
Project Context and Objectives:
The main purpose of this project is to reinforce cooperation between Azerbaijani and European researchers and to provide successful integration of the Institute of Physics at the Azerbaijan National Academy of Sciences (IPA) into European Research Area (ERA). The project serves the EU strategies for an “open ERA” as mentioned in the EC Communication for International S&T Cooperation by making highly qualified researchers from Azerbaijan available for scientific collaboration in Framework Programmes and other European research platforms. This action is in coherence with the concept of the “mutual interests of the EC and the ENP partner countries” as stated in the mentioned Communication. In this respect, the benefit of the consortium participants from the project comes by establishing close collaboration links and combining efforts in the research fields of mutual interest.
The economy of Azerbaijan is mainly based on oil profits. However, integration of Azerbaijan into the world market persistently calls for development of non-oil sectors of the economy, particularly, science-related fields of industry. On the other hand, depletion of fossil energy sources and world energy demand facilitate exploration of renewable energy sources and development of new materials for energy supply. This is one of the vital and common challenges the world faces in the twenty first century and joining the efforts and collaboration is a prerequisite of sustainable development.
The Government of Azerbaijan has adopted a state programme for the development of renewable energy sources and is taking significant actions towards realization of this programme in the country. In the last decade a number of power stations converting hydro and wind energy into electric power have been constructed throughout the country; efforts have been made for the development of production of solar panels and biofuel. The IPA is a primary organization in Azerbaijan involved in fundamental and applied research in the field and actively collaborating with research institutions abroad. Due to its suitable geographical location, developed infrastructure and qualified human resources Azerbaijan has a great potential for realization of ambitious research and development projects in the region of Caucasus and the Caspian Sea.
The PRIMA-ERA supports and facilitates research collaboration between IPA and research centres in the EU member and associate countries. In order to achieve strong strong research collaboration between participants, a network is established with the project’s Consortium Participant institutions to provide an effective exchange of knowledge, dissemination of research results, joint research plans and preparetion for future collaboration in EU programmes. The PRIMA-ERA involves Framework Programme awareness and knowledge building as well as direct twinning and networking activities in designated research fields between the following excellent research institutions - Consortium members.
The research topics are of mutual interests and they are the following:
1. Energy;
2. Nano-sciences and nanotechnologies, Materials, and Production of new technologies (NMP).
Research topic 'Energy' is covered by the folllowing sub-topics:
Development of new materials, device structures and fabrication methods for thin film solar cells
A1. Development of nanostructured window layers for CdTe and CIGS solar cells.
A2. Development and characterization of advanced thin film solar cells.
A3. Development of new rear- earth-doped materials for up-conversion of infrared solar energy in solar cells.
Research topic 'Nano-sciences and nanotechnologies' is covered by the following sub-topics:
Mastering nano-scale complexity in materials
B1. Computational design of new materials.
B2. Growth and characterisation of materials for spintronics-photovoltaics.
B3. Preparation of protective diamond-like coatings.
PRIMA-ERA project activities are performed in accordance with the general objectives which are described below.
1. Development of strategic research partnerships with European research institutions for IPA’s integration into ERA
2. Improve IPA’s regional scope and it’s responses to socio-economic needs
3. Improve IPA’s human potential
4. Increase job opportunities for young scientists in the country.
Project Results:
Thin film photovoltaic structures are of great research interest due to their attractiveness for high-efficiency low-cost solar cells. Chalcopyrite alloys of Cu (In, Ga, Al) (S, Se, Te) or CIGS have successfully been integrated into thin film solar cells over the last two decades. These materials exhibit excellent stability and their energy gaps can be tuned to 1.5 eV for photovoltaic application. Among the available thin film solar cells, CIGS solar cells display the highest efficiencies which are now approaching those of crystalline Si. However, there are still problems related to optimization of the solar cell structures and low-cost manufacturing process. CdTe cells is another class of promising solar cells with potential of improved efficiency. There are also problems to be solved related to improving of device parameters of solar cell window layers and coatings as well as exploring new materials for up-conversion photovoltraics.
Before joining to PRIMA-ERA collaboration, IRDEP (France) team has been successfully demonstrated that materials grown using wet chemistry processes for the preparation of nano-crystalline precursors can achieve the same performance as the best state-of-the art, e.g. conversion efficiencies above 11% for CuInS2. It has been revealed that due to the growth process, the active material inherits a porous morphology that has been shown to play an important role in the performance and functionality of the material. The new device morphology leads to a device operation similar to that of nanoscale organic interpenetrated solar cells or dye sensitized solar cells rather than to that of standard polycrystalline ones. IRDEP capabilities provide a broad range of technological advancement of photovoltaic materials.
At same time, IPA (Azerbaijan) team was successful in spectroscopic ellipsometry characterization of different single and polycrystalline inorganic materials, including CIGS. The advantage of the spectroscopic ellipsometry (SE) in comparison with other conventional optical techniques is that it provides accurate and precise Kramers-Kronig (KK) consistent determination of optical parameters as well as thickness for practically any single and multilayer structure. In addition, infrared ellipsometry yields important information on phonon structure and chemical composition of the layers. IPA’s state-of-the-art ellipsometric equipment provides experimental capability in the 190 – 33000 nm spectral region and 4 – 573 K temperature range.
Based on performed joint research during the implementation of the FP7 PRIMA-ERA project (2012-2014), the Institute of Physics of the Azerbaijan National Academy of Sciences (IPA) and the Institut de Recherche et Development sur l’Energie Photovoltaique (IRDEP) present obtained scientific results as follows:
A) Study on thin film solar cells and active layers
1. Preparation of CuIn1-xGaxSe2 (where x=0.29) thin films on Mo substrates by Evaporation from 4 independent sources at IRDEP for test of the buffer layer at IPA. Standard characterization (X-ray diffraction and elemental analysis, standard IRDEP process of solar cells and testing) were used to check the films were suitable for their solar cell application.
These films were then characterized by spectroscopic ellipsometry.
2. Nanostructured CdS:O films have been prepared at IPA by magnetron sputtering method and transferred at IRDEP. Spectroscopic ellipsometry (IPA), X-ray diffraction and elemental analysis (IRDEP), Atomic Force and Transmission Electron Microscopy studies (IPA) were used for the characterization of the films. We examined the nano-structure and optical properties of CdS:O films deposited by magnetron sputtering. Nano-crystals in annealed CdS:O films were observed in TEM images, with crystal diameters ranging from 5 – 20 nm. Amorphous CdS:O phases were crystallized by annealing at 300 ºC. We observed PL emission located at 3.35 eV at room temperature in CdS:O film annealed at 400 ºC. Besides, almost complete smearing of band gap spectral feature is observed for CdS:O films deposited at 5% value of O/Ar ratio, resulting in appreciable transparency of the films in a spectral range above the energy gap of CdS. An increase in transparency of the CdS:O (5%) and observed PL emission located at 3.35 eV can be caused by several factors including redistribution of the density of states in amorphous CdS, quantum size effect in nano-crystals of CdS, and contribution of amorphous CdO2.
B) Study of TCO and optical layers for thin film solar cells
1. ZnO and ZnO:Al thin films as TCO for thin film solar cells: Zinc oxide is a direct wide band gap semiconductor material with high exciton binding energy. Undoped and metal-doped ZnO are of great interest for utilization as transparent conducting layer stack in thin film solar cells (fig below). Intrinsic ZnO, when deposited as a thin layer, exhibits oxygen deficiency introducing defect states in the electronic structure of the material that may affect the overall device performance. Addition of oxygen during deposition is intended to prevent the defect formation.
Despite of bulk materials, thin films introduce additional challenges on quick and precise determation of their optical parameters, associated with size effect due to small thicknesses, surface and interface effects in complex multilayer structures, difficulty of tailoring of their properties, and others. The effect of oxygen addition on optical parameters and dielectric function of the films can be monitored by spectroscopic ellipsometry.
ZnO films studied were deposited by means of magnetron sputtering onto 2 mm thick soda–lime–glass (SLG) substrates. Oxygen was introduced during sputtering and its concentration defined as Ar/O2 pressure ratio in the deposition chamber was 0.5 1, 2, 4 and 8%. Deposition time for all the samples was kept constant that resulted in thicknesses of the films as 69, 60, 45, 40 and 30 nm from the lowest to the highest oxygen concentration, respectively. The thicknesses were measured after the deposition by grazing angle X-ray diffraction technique (GAXRD). Further details on growth conditions can be found elsewhere. The films were confirmed by XRD to have optical axis perpendicular to the surface that made suitable utilization of standard ellipsometric measurements without consideration of anisotropic effects. The XRD measurements revealed improved crystallinity of the films with addition of oxygen into deposition chamber. The ellipsometric measurements in 220–1700 nm and 2–25 μm spectral ranges were performed using Woollam M2000 and IR-VASE rotating compensator instruments, respectively. Incident light angles were varied between 50 and 60° with 5° step. Infrared measurements were performed with 2 cm−1 resolution. WVASE32 computer program was used for the ellipsometric data fitting procedure. Experimental data were fitted (employing the Levenberg–Marquardt algorithm) to optical model using parameterized model dielectric functions simultaneously for all the data points measured in UV/VIS/NIR and mid-IR spectral ranges. Surface roughness/ZnO/SLG three-phase model was used for fitting the data. Surface roughness has been modelled using Bruggeman effective medium approximation with 50% voids. The free substrate was measured and fitted separately to obtain its optical parameters for inclusion into the model. Further data from both UV/ VIS/NIR and mid-IR measurements were fitted at the same time. This approach allows indirectly to relate the experimental data to electronic and structural properties of the samples.
An oscillator model has been used for simulation of the ZnO dielectric function. For the UV/VIS/NIR region we use Gaussian and parameterized semiconductor oscillator (P semi oscillator available in the WVASE32) functions to model high energy and band edge region, respectively, and another Gaussian for the NIR part of the dielectric function. The figure below represents the UV/VIS/NIR experimental data along with model fit for sample prepared with 2% oxygen in the deposition chamber. Thickness and oscillator parameters are used as the fitting parameters.
Evolution of the dielectric function line shape in the band edge region with increasing oxygen concentration from 0.5 to 8% has been found. Addition of up to 2% oxygen during deposition compensates for oxygen deficiency and leads to formation of less defective films. Further increase of oxygen concentration, however, leads to instability of optical parameters of the samples. The results suggest near 2% oxygen concentration as optimal for preparation of optically stable ZnO thin films. Infrared dielectric function of the film prepared with 2% oxygen has also been found. All these parameters were very important to improve the solar cells TCO layer.
2. Preparation of Y2O3 films for upconversion solar cells application to utilize solar energy from IR spectral range.
Preparation technology of Y2O3 films with rare earth incorporated was prepared using appropriate composition of yttrium erbium and ytterbium nitrates (3 mg) (99.9%, Alfa Aesar), that were mixed and dissolved deionized water (Solution A). Alternatively, Citric acid, with a molar ratio of 1:1 with the metal nitrates, were dissolved separately in 9 ml of water (Solution B). After the total dissolution, solution B was added in drops to solution and kept stirred 2 h more after the end of mixing to obtain a transparent solution. The as-prepared solution was then aged at least 24 h at room temperature without stirring. This initial solution was filtered through 0.2 μm filter syringes and deposited on silicon substrates by spin coating.
The as-deposited films were dried at 100°C, fired at 600°C for one hour to remove organics and this procedure was repeated 10 times before final annealing at 800°C during 2 hours.. The concentrations of dopants were 1% Er, 1% Er - 3% Yb, and 10% Er - 3% Yb and the film thicknesses measured with a Dektak profilometer were around 240 nm. To check up on homogeneity of the films designed for spectroscopic ellipsometry study, a preliminary examination of their surfaces and observation of the photoluminescence induced by rare earth dopants were made using a Nanofinder 30 confocal laser microscopy system (Tokyo Instruments Inc., Japan). The obtained thin films were homogeneous for the most part but turned out to have some parts which were optically different from the rest of the film. The reasons leading to the formation of the above distinct regions were clarified using confocal spectroscopic microscopy of the obtained rare earth doped Y2O3 films.
As can be concluded from the figure below the totally polarized light of the probe beam transforms into partially polarized light after reflection from the film surface. Similar but not the same depolarization spectra are registered from the other samples studied in this work. Generally, the depolarization effect in the studied samples takes place in a spectral range below 600 nm and is represented by a number of rather narrow peaks separated by pretty wide regions that are free of depolarization. All samples are non-depolarizing starting from at least 600 nm into the near IR region (up to 1680 nm). Note that the above mentioned peculiarities of the depolarization effect in the studied rare earth doped Y2O3 films are very important for elaborating an optical model for these films. The point is that, strictly speaking, depolarizing samples can hardly be modeled in terms of a layered system consisting of the effective medium layers with plane parallel interfaces. For example, the presence of scattering, including multiple scattering that is commonly responsible for the depolarization, results in ellipsometric Psi and Delta which are no longer unique and unambiguously connected with optical constants of the material even in the case of isotropic media. Therefore depolarization free spectral regions are very helpful for elaboration of the reasonable optical models. In our case these regions are quite wide, allowing for the meaningful effective medium modelling.
C) Studies on advanced III-V devices for high efficiency solar energy application
I. Goals of measurements
1. On InP-based diode, the main goal was to characterize electrical properties of two samples. A side goal was to know the etching base roughness.
2. On bulk InP with and without polyphosphazen film, the possible change on optical properties due to the presence of polyphosphazen was of interest.
3. On PMMA-based samples, the goal was to measure n and k, with and without dye.
II. What has been done
1. AFM measurements were performed on the two nano-diode samples. Current-voltage measurements by conductive probe AFM (AFMCP) were not feasible in Baku. The samples stayed in Baku in order to bring them somewhere else to be able to do these measurements.
Nevertheless, KPF has been done, in two different configurations : dark and light conditions.
In addition, the side-goal mentionned in I.1.has been reached and the etching based roughness was found to be less than 10 nm.
2. Visible ellipsometric measurements were performed on all my samples with different angles every 5°. It was not enough to be able to detect the Brewster angle.
3. Visible ellipsometric measurements were performed in order to highlight changes on n and k with the dye. n values were slightly above 1.5 but k values were almost similar with and without dye.
Potential Impact:
Republic of Azerbaijan is the largest country in the South Caucasus region of Eurasia. Known for its wealth of crude oil and natural gas reserves, Azerbaijan is bounded by the Caspian Sea to the east, Russia to the north, Georgia to the northwest, Armenia to the west, and Iran to the south.
Labour markets in Azerbaijan have been through a turbulent transition, with periods of low economic activity, high unemployment and underemployment, and frequent job changes for individuals. These changes, however, have been essential to the economic transformation process, leading to productivity increases and consequently better wages for employees.
Oil and gas, machinery, cotton, foodstuffs are in the top of listed exporting goods from country. Main export partners of Azerbaijan Republic are Italy (26.8%), United States (8.4%), Germany (7.1%), France (6.7%), Czech Republic (4.9%) and Russia (4.4%). Machinery and equipment, foodstuffs, metals, chemicals are main import goods to the country. Main import partners of Azerbaijan Republic are Turkey (17.7%), Russia (14.5%), Germany (9.9%), China (9.6%), United Kingdom (7.2%) and Ukraine (7.0%).
Institute of Physics was established in 1945 as a research unit within the Azerbaijan National Academy of Sciences. It is the leading research organization in physical sciences in Azerbaijan. Up to date IPA industry relationships are not satisfactory. This problem is partly related to overall difficult economic conditions in the country in the recent past and partly to low level of experimental works at the Institute due to outdated experimental equipment. However, recent renovation of experimental capabilities provides good basis for market orientation of the IPA.
Action plan of the project and planned activities will allow IPA to find its place in ERA. During project execution, IPA organised three Open Days, which was completely new approach for research institutes of Azerbaijan. Various society members of the republic received opportunity to get detailed iformation about activities of IPA and its staff.
Also, evaluation of current research activities at IPA and foresight analysis in view of their adequacy to socio-economic needs in the near-term outlook was performed aiming to start short- and long-term reforms in IPA structure, which will lead to its integration with ERA. Final version of the report of evaluation of current research activities at IPA and foresight analysis in view of their adequacy to socio-economic needs in the near-term outlook was submitted to different ministeries and research related NGOs of the country.
IPA and IRDEP performed successful joint experiments and their results have been published in two international journals:
1. Mammadov, E., N. Naghavi, Z. Jehl, G. Renou, T. Tiwald, N. Mamedov, D. Lincot, et J.-F. Guillemoles. « Dielectric Function of Zinc Oxide Thin Films in a Broad Spectral Range ». Thin Solid Films 571 (novembre 2014): 593 96. doi:10.1016/j.tsf.2014.02.004.
2. Gasimov, Naghi, Eldar Mammadov, Anne L. Joudrier, Sardar Babayev, Irada Mamedova, Christian Andriamiadamanana, Nazim Mamedov, Negar Naghavi, et Jean F. Guillemoles. « Depolarization Effect in Rare-Earth Doped Y2O3 Films in Blue and UV Spectral Range ». Physica Status Solidi (c), 7 avril 2015, n/a n/a. doi:10.1002/pssc.201400301.
Additional to mentioned above activities, number of research and training based staff exchanges successfully performed between three participating institutes. Also, TUBITAK (Turkey) organized traoning seminar for Azerbaijani researchers with main goal on their awareness on forthcoming H2020 calls relevant to research topics of PRIMA-ERA and trained them on good proposal writing and formation of successfull collaborations for H2020.
List of Websites:
www.prima-era.gov.az
Dr. Elchin Jafarov
Institute of Physics
Azerbaijan National Academy of Sciences
Javid av. 33, AZ-1143
Baku, Azerbaijan
e-mail: ejafarov@physics.ab.az
Main goal of the PRIMA-ERA project is reinforce research collaboration between the Institute of Physics, Azerbaijan National Academy of Sciences (IPA) and research centres in the European Research Area. The IPA is a leading organization on scientific research, knowledge transfer and graduate education in physics in Azerbaijan. PRIMA-ERA will facilitate the collaboration of the IPA with research centres in EU member and associate countries and reinforce its engagement in the FP7 projects in research topics covered by such thematic priorities as energy and nanotechnologies.
The primary objectives of the project are:
- to increase IPA capacities and preparedness for collaboration in the FP7 through twinning and networking, development of joint research plans and training modules and trainings;
- to increase visibility of IPA for international scientific community and other stakeholders through dissemination of scientific information and promotional activities;
- to ensure the compliance of the IPA’s research activities with socio-economic needs of the country and regionally and provide better career opportunities for young scientists through encouragement innovative approaches and development of research strategy.
The project consortium between the IPA, CNRS Institut de Recherche et Development sur l’Energie Photovoltaique, CNRS-IRDEP (France) and TUBITAK – Marmara Research Centre, TUBITAK - MAM (Turkey), has been established to effectively fulfill the project’s objectives.
The PRIMA-ERA complies with the EU strategies for an “open ERA” as mentioned in the EC Communication for International S&T Cooperation by providing mobility and access to research facilities between the centres with similar research interests. The project actions are in coherence with the concept of the “mutual interests of the EC and the ENP partner countries” as stated in the mentioned Communication.
Project Context and Objectives:
The main purpose of this project is to reinforce cooperation between Azerbaijani and European researchers and to provide successful integration of the Institute of Physics at the Azerbaijan National Academy of Sciences (IPA) into European Research Area (ERA). The project serves the EU strategies for an “open ERA” as mentioned in the EC Communication for International S&T Cooperation by making highly qualified researchers from Azerbaijan available for scientific collaboration in Framework Programmes and other European research platforms. This action is in coherence with the concept of the “mutual interests of the EC and the ENP partner countries” as stated in the mentioned Communication. In this respect, the benefit of the consortium participants from the project comes by establishing close collaboration links and combining efforts in the research fields of mutual interest.
The economy of Azerbaijan is mainly based on oil profits. However, integration of Azerbaijan into the world market persistently calls for development of non-oil sectors of the economy, particularly, science-related fields of industry. On the other hand, depletion of fossil energy sources and world energy demand facilitate exploration of renewable energy sources and development of new materials for energy supply. This is one of the vital and common challenges the world faces in the twenty first century and joining the efforts and collaboration is a prerequisite of sustainable development.
The Government of Azerbaijan has adopted a state programme for the development of renewable energy sources and is taking significant actions towards realization of this programme in the country. In the last decade a number of power stations converting hydro and wind energy into electric power have been constructed throughout the country; efforts have been made for the development of production of solar panels and biofuel. The IPA is a primary organization in Azerbaijan involved in fundamental and applied research in the field and actively collaborating with research institutions abroad. Due to its suitable geographical location, developed infrastructure and qualified human resources Azerbaijan has a great potential for realization of ambitious research and development projects in the region of Caucasus and the Caspian Sea.
The PRIMA-ERA supports and facilitates research collaboration between IPA and research centres in the EU member and associate countries. In order to achieve strong strong research collaboration between participants, a network is established with the project’s Consortium Participant institutions to provide an effective exchange of knowledge, dissemination of research results, joint research plans and preparetion for future collaboration in EU programmes. The PRIMA-ERA involves Framework Programme awareness and knowledge building as well as direct twinning and networking activities in designated research fields between the following excellent research institutions - Consortium members.
The research topics are of mutual interests and they are the following:
1. Energy;
2. Nano-sciences and nanotechnologies, Materials, and Production of new technologies (NMP).
Research topic 'Energy' is covered by the folllowing sub-topics:
Development of new materials, device structures and fabrication methods for thin film solar cells
A1. Development of nanostructured window layers for CdTe and CIGS solar cells.
A2. Development and characterization of advanced thin film solar cells.
A3. Development of new rear- earth-doped materials for up-conversion of infrared solar energy in solar cells.
Research topic 'Nano-sciences and nanotechnologies' is covered by the following sub-topics:
Mastering nano-scale complexity in materials
B1. Computational design of new materials.
B2. Growth and characterisation of materials for spintronics-photovoltaics.
B3. Preparation of protective diamond-like coatings.
PRIMA-ERA project activities are performed in accordance with the general objectives which are described below.
1. Development of strategic research partnerships with European research institutions for IPA’s integration into ERA
2. Improve IPA’s regional scope and it’s responses to socio-economic needs
3. Improve IPA’s human potential
4. Increase job opportunities for young scientists in the country.
Project Results:
Thin film photovoltaic structures are of great research interest due to their attractiveness for high-efficiency low-cost solar cells. Chalcopyrite alloys of Cu (In, Ga, Al) (S, Se, Te) or CIGS have successfully been integrated into thin film solar cells over the last two decades. These materials exhibit excellent stability and their energy gaps can be tuned to 1.5 eV for photovoltaic application. Among the available thin film solar cells, CIGS solar cells display the highest efficiencies which are now approaching those of crystalline Si. However, there are still problems related to optimization of the solar cell structures and low-cost manufacturing process. CdTe cells is another class of promising solar cells with potential of improved efficiency. There are also problems to be solved related to improving of device parameters of solar cell window layers and coatings as well as exploring new materials for up-conversion photovoltraics.
Before joining to PRIMA-ERA collaboration, IRDEP (France) team has been successfully demonstrated that materials grown using wet chemistry processes for the preparation of nano-crystalline precursors can achieve the same performance as the best state-of-the art, e.g. conversion efficiencies above 11% for CuInS2. It has been revealed that due to the growth process, the active material inherits a porous morphology that has been shown to play an important role in the performance and functionality of the material. The new device morphology leads to a device operation similar to that of nanoscale organic interpenetrated solar cells or dye sensitized solar cells rather than to that of standard polycrystalline ones. IRDEP capabilities provide a broad range of technological advancement of photovoltaic materials.
At same time, IPA (Azerbaijan) team was successful in spectroscopic ellipsometry characterization of different single and polycrystalline inorganic materials, including CIGS. The advantage of the spectroscopic ellipsometry (SE) in comparison with other conventional optical techniques is that it provides accurate and precise Kramers-Kronig (KK) consistent determination of optical parameters as well as thickness for practically any single and multilayer structure. In addition, infrared ellipsometry yields important information on phonon structure and chemical composition of the layers. IPA’s state-of-the-art ellipsometric equipment provides experimental capability in the 190 – 33000 nm spectral region and 4 – 573 K temperature range.
Based on performed joint research during the implementation of the FP7 PRIMA-ERA project (2012-2014), the Institute of Physics of the Azerbaijan National Academy of Sciences (IPA) and the Institut de Recherche et Development sur l’Energie Photovoltaique (IRDEP) present obtained scientific results as follows:
A) Study on thin film solar cells and active layers
1. Preparation of CuIn1-xGaxSe2 (where x=0.29) thin films on Mo substrates by Evaporation from 4 independent sources at IRDEP for test of the buffer layer at IPA. Standard characterization (X-ray diffraction and elemental analysis, standard IRDEP process of solar cells and testing) were used to check the films were suitable for their solar cell application.
These films were then characterized by spectroscopic ellipsometry.
2. Nanostructured CdS:O films have been prepared at IPA by magnetron sputtering method and transferred at IRDEP. Spectroscopic ellipsometry (IPA), X-ray diffraction and elemental analysis (IRDEP), Atomic Force and Transmission Electron Microscopy studies (IPA) were used for the characterization of the films. We examined the nano-structure and optical properties of CdS:O films deposited by magnetron sputtering. Nano-crystals in annealed CdS:O films were observed in TEM images, with crystal diameters ranging from 5 – 20 nm. Amorphous CdS:O phases were crystallized by annealing at 300 ºC. We observed PL emission located at 3.35 eV at room temperature in CdS:O film annealed at 400 ºC. Besides, almost complete smearing of band gap spectral feature is observed for CdS:O films deposited at 5% value of O/Ar ratio, resulting in appreciable transparency of the films in a spectral range above the energy gap of CdS. An increase in transparency of the CdS:O (5%) and observed PL emission located at 3.35 eV can be caused by several factors including redistribution of the density of states in amorphous CdS, quantum size effect in nano-crystals of CdS, and contribution of amorphous CdO2.
B) Study of TCO and optical layers for thin film solar cells
1. ZnO and ZnO:Al thin films as TCO for thin film solar cells: Zinc oxide is a direct wide band gap semiconductor material with high exciton binding energy. Undoped and metal-doped ZnO are of great interest for utilization as transparent conducting layer stack in thin film solar cells (fig below). Intrinsic ZnO, when deposited as a thin layer, exhibits oxygen deficiency introducing defect states in the electronic structure of the material that may affect the overall device performance. Addition of oxygen during deposition is intended to prevent the defect formation.
Despite of bulk materials, thin films introduce additional challenges on quick and precise determation of their optical parameters, associated with size effect due to small thicknesses, surface and interface effects in complex multilayer structures, difficulty of tailoring of their properties, and others. The effect of oxygen addition on optical parameters and dielectric function of the films can be monitored by spectroscopic ellipsometry.
ZnO films studied were deposited by means of magnetron sputtering onto 2 mm thick soda–lime–glass (SLG) substrates. Oxygen was introduced during sputtering and its concentration defined as Ar/O2 pressure ratio in the deposition chamber was 0.5 1, 2, 4 and 8%. Deposition time for all the samples was kept constant that resulted in thicknesses of the films as 69, 60, 45, 40 and 30 nm from the lowest to the highest oxygen concentration, respectively. The thicknesses were measured after the deposition by grazing angle X-ray diffraction technique (GAXRD). Further details on growth conditions can be found elsewhere. The films were confirmed by XRD to have optical axis perpendicular to the surface that made suitable utilization of standard ellipsometric measurements without consideration of anisotropic effects. The XRD measurements revealed improved crystallinity of the films with addition of oxygen into deposition chamber. The ellipsometric measurements in 220–1700 nm and 2–25 μm spectral ranges were performed using Woollam M2000 and IR-VASE rotating compensator instruments, respectively. Incident light angles were varied between 50 and 60° with 5° step. Infrared measurements were performed with 2 cm−1 resolution. WVASE32 computer program was used for the ellipsometric data fitting procedure. Experimental data were fitted (employing the Levenberg–Marquardt algorithm) to optical model using parameterized model dielectric functions simultaneously for all the data points measured in UV/VIS/NIR and mid-IR spectral ranges. Surface roughness/ZnO/SLG three-phase model was used for fitting the data. Surface roughness has been modelled using Bruggeman effective medium approximation with 50% voids. The free substrate was measured and fitted separately to obtain its optical parameters for inclusion into the model. Further data from both UV/ VIS/NIR and mid-IR measurements were fitted at the same time. This approach allows indirectly to relate the experimental data to electronic and structural properties of the samples.
An oscillator model has been used for simulation of the ZnO dielectric function. For the UV/VIS/NIR region we use Gaussian and parameterized semiconductor oscillator (P semi oscillator available in the WVASE32) functions to model high energy and band edge region, respectively, and another Gaussian for the NIR part of the dielectric function. The figure below represents the UV/VIS/NIR experimental data along with model fit for sample prepared with 2% oxygen in the deposition chamber. Thickness and oscillator parameters are used as the fitting parameters.
Evolution of the dielectric function line shape in the band edge region with increasing oxygen concentration from 0.5 to 8% has been found. Addition of up to 2% oxygen during deposition compensates for oxygen deficiency and leads to formation of less defective films. Further increase of oxygen concentration, however, leads to instability of optical parameters of the samples. The results suggest near 2% oxygen concentration as optimal for preparation of optically stable ZnO thin films. Infrared dielectric function of the film prepared with 2% oxygen has also been found. All these parameters were very important to improve the solar cells TCO layer.
2. Preparation of Y2O3 films for upconversion solar cells application to utilize solar energy from IR spectral range.
Preparation technology of Y2O3 films with rare earth incorporated was prepared using appropriate composition of yttrium erbium and ytterbium nitrates (3 mg) (99.9%, Alfa Aesar), that were mixed and dissolved deionized water (Solution A). Alternatively, Citric acid, with a molar ratio of 1:1 with the metal nitrates, were dissolved separately in 9 ml of water (Solution B). After the total dissolution, solution B was added in drops to solution and kept stirred 2 h more after the end of mixing to obtain a transparent solution. The as-prepared solution was then aged at least 24 h at room temperature without stirring. This initial solution was filtered through 0.2 μm filter syringes and deposited on silicon substrates by spin coating.
The as-deposited films were dried at 100°C, fired at 600°C for one hour to remove organics and this procedure was repeated 10 times before final annealing at 800°C during 2 hours.. The concentrations of dopants were 1% Er, 1% Er - 3% Yb, and 10% Er - 3% Yb and the film thicknesses measured with a Dektak profilometer were around 240 nm. To check up on homogeneity of the films designed for spectroscopic ellipsometry study, a preliminary examination of their surfaces and observation of the photoluminescence induced by rare earth dopants were made using a Nanofinder 30 confocal laser microscopy system (Tokyo Instruments Inc., Japan). The obtained thin films were homogeneous for the most part but turned out to have some parts which were optically different from the rest of the film. The reasons leading to the formation of the above distinct regions were clarified using confocal spectroscopic microscopy of the obtained rare earth doped Y2O3 films.
As can be concluded from the figure below the totally polarized light of the probe beam transforms into partially polarized light after reflection from the film surface. Similar but not the same depolarization spectra are registered from the other samples studied in this work. Generally, the depolarization effect in the studied samples takes place in a spectral range below 600 nm and is represented by a number of rather narrow peaks separated by pretty wide regions that are free of depolarization. All samples are non-depolarizing starting from at least 600 nm into the near IR region (up to 1680 nm). Note that the above mentioned peculiarities of the depolarization effect in the studied rare earth doped Y2O3 films are very important for elaborating an optical model for these films. The point is that, strictly speaking, depolarizing samples can hardly be modeled in terms of a layered system consisting of the effective medium layers with plane parallel interfaces. For example, the presence of scattering, including multiple scattering that is commonly responsible for the depolarization, results in ellipsometric Psi and Delta which are no longer unique and unambiguously connected with optical constants of the material even in the case of isotropic media. Therefore depolarization free spectral regions are very helpful for elaboration of the reasonable optical models. In our case these regions are quite wide, allowing for the meaningful effective medium modelling.
C) Studies on advanced III-V devices for high efficiency solar energy application
I. Goals of measurements
1. On InP-based diode, the main goal was to characterize electrical properties of two samples. A side goal was to know the etching base roughness.
2. On bulk InP with and without polyphosphazen film, the possible change on optical properties due to the presence of polyphosphazen was of interest.
3. On PMMA-based samples, the goal was to measure n and k, with and without dye.
II. What has been done
1. AFM measurements were performed on the two nano-diode samples. Current-voltage measurements by conductive probe AFM (AFMCP) were not feasible in Baku. The samples stayed in Baku in order to bring them somewhere else to be able to do these measurements.
Nevertheless, KPF has been done, in two different configurations : dark and light conditions.
In addition, the side-goal mentionned in I.1.has been reached and the etching based roughness was found to be less than 10 nm.
2. Visible ellipsometric measurements were performed on all my samples with different angles every 5°. It was not enough to be able to detect the Brewster angle.
3. Visible ellipsometric measurements were performed in order to highlight changes on n and k with the dye. n values were slightly above 1.5 but k values were almost similar with and without dye.
Potential Impact:
Republic of Azerbaijan is the largest country in the South Caucasus region of Eurasia. Known for its wealth of crude oil and natural gas reserves, Azerbaijan is bounded by the Caspian Sea to the east, Russia to the north, Georgia to the northwest, Armenia to the west, and Iran to the south.
Labour markets in Azerbaijan have been through a turbulent transition, with periods of low economic activity, high unemployment and underemployment, and frequent job changes for individuals. These changes, however, have been essential to the economic transformation process, leading to productivity increases and consequently better wages for employees.
Oil and gas, machinery, cotton, foodstuffs are in the top of listed exporting goods from country. Main export partners of Azerbaijan Republic are Italy (26.8%), United States (8.4%), Germany (7.1%), France (6.7%), Czech Republic (4.9%) and Russia (4.4%). Machinery and equipment, foodstuffs, metals, chemicals are main import goods to the country. Main import partners of Azerbaijan Republic are Turkey (17.7%), Russia (14.5%), Germany (9.9%), China (9.6%), United Kingdom (7.2%) and Ukraine (7.0%).
Institute of Physics was established in 1945 as a research unit within the Azerbaijan National Academy of Sciences. It is the leading research organization in physical sciences in Azerbaijan. Up to date IPA industry relationships are not satisfactory. This problem is partly related to overall difficult economic conditions in the country in the recent past and partly to low level of experimental works at the Institute due to outdated experimental equipment. However, recent renovation of experimental capabilities provides good basis for market orientation of the IPA.
Action plan of the project and planned activities will allow IPA to find its place in ERA. During project execution, IPA organised three Open Days, which was completely new approach for research institutes of Azerbaijan. Various society members of the republic received opportunity to get detailed iformation about activities of IPA and its staff.
Also, evaluation of current research activities at IPA and foresight analysis in view of their adequacy to socio-economic needs in the near-term outlook was performed aiming to start short- and long-term reforms in IPA structure, which will lead to its integration with ERA. Final version of the report of evaluation of current research activities at IPA and foresight analysis in view of their adequacy to socio-economic needs in the near-term outlook was submitted to different ministeries and research related NGOs of the country.
IPA and IRDEP performed successful joint experiments and their results have been published in two international journals:
1. Mammadov, E., N. Naghavi, Z. Jehl, G. Renou, T. Tiwald, N. Mamedov, D. Lincot, et J.-F. Guillemoles. « Dielectric Function of Zinc Oxide Thin Films in a Broad Spectral Range ». Thin Solid Films 571 (novembre 2014): 593 96. doi:10.1016/j.tsf.2014.02.004.
2. Gasimov, Naghi, Eldar Mammadov, Anne L. Joudrier, Sardar Babayev, Irada Mamedova, Christian Andriamiadamanana, Nazim Mamedov, Negar Naghavi, et Jean F. Guillemoles. « Depolarization Effect in Rare-Earth Doped Y2O3 Films in Blue and UV Spectral Range ». Physica Status Solidi (c), 7 avril 2015, n/a n/a. doi:10.1002/pssc.201400301.
Additional to mentioned above activities, number of research and training based staff exchanges successfully performed between three participating institutes. Also, TUBITAK (Turkey) organized traoning seminar for Azerbaijani researchers with main goal on their awareness on forthcoming H2020 calls relevant to research topics of PRIMA-ERA and trained them on good proposal writing and formation of successfull collaborations for H2020.
List of Websites:
www.prima-era.gov.az
Dr. Elchin Jafarov
Institute of Physics
Azerbaijan National Academy of Sciences
Javid av. 33, AZ-1143
Baku, Azerbaijan
e-mail: ejafarov@physics.ab.az