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Towards Roll-to-Roll Production of Third Generation Solar Cells

Periodic Reporting for period 1 - R2R-3G (Towards Roll-to-Roll Production of Third Generation Solar Cells)

Reporting period: 2016-06-01 to 2018-05-31

The world energetic demand keeps growing and it is expected to be 850 Quadrillion Btu in 2040. The traditional energetic technology based on fossil fuels can solve the actual demand but it cannot assure the future consumption. In addition, the use of these technologies produces harmful effects for the environment affecting the human life quality and other living beings. This energetic demand problem has especial relevance in Europe since it imports more than half of the energy it consumes making it vulnerable to external suppliers.
Europe is working to invert this situation with programs like EU Framework Programme for Research and Innovation with the challenge “Secure, Clean and Efficient Energy” in Horizon 2020 program. It is accepted that the energy solution will be a combination of technologies based on fossil fuels with a progressive increment in the use of renewable energies. The photovoltaic technology will be an important part of a multi-component solution due to the fact that the solar energy is the biggest renewable source reaching the Earth crust with a total energy amount of 23.000 TW/year. Also, this technology can be implemented in urban areas such as roofs, building surfaces or other areas as fallow land, deserts, etc. This makes photovoltaic technology suitable for the development of smart cities.
The photovoltaic technologies have achieved important advances in the efficiency-cost ratio but they still need some more effort to be competitive in the actual energetic market. The scientific community is tackling this challenge with different approaches. Current photovoltaic technologies based on Silicon wafer - also called first generation - require more effort for increasing the efficiency/cost ratio of the solar panel. The actual tendencies value different alternatives. Some of these alternatives are based on: 1) the use of thin films - also called second generation - using Earth crust abundant materials for the active layer; 2) less expensive manufacturing protocols based on Roll-to-Roll processes and/or 3) the use of new solar cell architectures such as nanowires (NWs) (also called third generation), photonic crystals, monolayers, etc. The milestone of the photovoltaic technologies should be related with a mixture of these tendencies. The overall objective of R2R-3G project is to combine two of these approaches based on the use of highly efficient NWs solar technology and vacuum Roll-to-Roll processes.
One of the most interesting discoveries originated from this project is the fabrication of NWs using a novel protocol that allows the growth of supported NWs avoiding electron beam lithography in its fabrication in any way (direct or indirect). In that work I have put the emphasis on the role of the seed nanoparticles that determine the quality of the NWs. This protocol controls the main parameters of the NWs such as their diameter, length, etc. Besides, the efficiency of the solar cells made using this method demonstrated the special relevance of the study of the electrical issues in NW solar cells. This has to be addressed by the correct passivation of the surface of the NWs.
Another important contribution of my work to the field of NW solar cells is the identification of the mechanisms that allow the growth of NWs with high aspect ratio and good homogeneity using metal organic chemical vapour deposition. In that work, I demonstrated the influence of the dopant concentration in order to increase the homogeneity of the NW array. Besides, I showed that this fabrication method for solar cells can be extended to other systems that can benefit from these results. In addition, I successfully developed a novel protocol to make NWs on cheap substrates avoiding the epitaxial growth. This preliminary work has proven to be important for the cost reduction of the fabrication of NWs devices.
Up to date, the published results derived from this project have been disseminated in the following peer-reviewed articles, meetings and conferences:
L. Francaviglia et al, 2018, 10.1021/acs.na006Eolett.7b05402
A. Dorodnyy et al, 2018, 10.1109/JSTQE.2018.2840339

- P. Romero-Gomez. LMPV Symposium June 2016. Light trapping in semitransparent organic solar cells. FOM institute Amolf, Amsterdam.
- D. Mikulik, P. Romero-Gomez, M. Ricci, G. Tutuncuoglu, F. Matteini, J. Vukajlovic, N. Vulic, M. Friedl, E. Alarcon-Llado, B. Dwir, A. Rudra, E. Kapon and A. Fontcuberta i Morral “From single NW solar cell to large scale NW array solar cell development through Conductive AFM analysis”, MRS spring, Phoenix, USA, 2017.
- D. Mikulik, M. Ricci, P. Romero-Gomez, G. Tutuncuoglu, F. Matteini, J. Vukajlovic, E. Alarcon-Llado and A. Fontcuberta i Morral “Single nanowire current‐voltage measurements by C-AFM and its effect on the output characteristics of solar cells based on nanowire ensembles” EMC17, South Bend, USA, 2017.
- A. Rudra, D. Mikulik, P. Romero Gomez, B. Dwir, A. Fontcuberta i Morral, E. Kapon “High temperature selective area metalorganic vapour phase epitaxy of GaAs nanowires using N2 as carrier gas” ORAL, EW-MOVPE17, France, 2017.
- P. Romero Gomez, D. Mikulik, G. Tutuncuoglu, H. Potts, M. Friedl, A. Fontcuberta i Morral “Large Scale Nanowire Solar Cells” Poster, Congrès Photovoltaïque National, Lausanne, Switzerland, 2017.
- P. Romero Gomez, D. Mikulik, G. Tutuncuoglu, H. Potts, M. Friedl, J. Vukajlovik-Plestina, B. Dwir, A. Rudra, E. Kapon, A. Fontcuberta i Morral “Robust nanowire arrays for new generation solar cells” Nanowire Week, Lund Sweden, 2017.
- D. Mikulik, M. Mintairov, V. Evstropov, P. Romero-Gomez, M. Shvarts, A. Fontcuberta I Morral “Intrinsic device properties of nanowire based solar cells using intensity-dependent measurements up to 1000 suns” ICPS, Montpellier, France, 2018.
- D Mikulik, Andrew C. Meng, Riad Berrazouane, P. Romero-Gomez, K. Tang, A. Fontcuberta i Morral, P. C. Mcintyre “Electrochemical Impedance Spectroscopy method to analyse interface states in semiconductor-oxide high-aspect-ratio structures” ICPS, Montpellier, France, 2018.
In general, I had the greatest chance to contribute to the advancement of the integration of roll to roll processes for the production of third generation solar cells. Overall, the results derived from this project have: i) achieved high quality of the growth NWs, ii) filled the technological gap in basic knowledge of fabrication of NWs on cheap substrates, iii) identified the materials to fabricate flexible NW solar cells devices, and iv) brought advances to the understanding of electrical issues in flexible solar cells. Thus, the results of R2R-3G project will have high impact in Europe since they help the possible integration of third generation solar cells as renewable energy in the electricity market.
Example of flexible NWSC devices in two configurations: transparent and opaque