Significance Statement
In the recent years, thin film solar cell manufacturers have suffered from the abrupt decrease of silicon module price. Irrespective of the current efficiency of Cu(In, Ga) Se2 thin film solar cells being very near to the already established silicon-based photovoltaic technology, the low availability of gallium and indium in the Earth’s crust will result in their high cost, and this will definitely limit their future role in terawatt range photovoltaic applications. Therefore, researchers have shifted their attention to low cost materials based on earth abundant elements.
Fortunately, there is an attractive alternative for the preparation of indium and gallium free terawatt-scale chalcogenides. These alternatives depend on I2-II-IV-VI4 species, which include copper zin tin sulfide, copper zinc tin selenide and the related sulphur-selenium alloy. Copper manganese tin sulfide, a p-type semiconductor based fully on earth abundant as well as low cost elements, is another member of this group of materials . In view of the fact that manganese is cheaper than zinc, copper manganese tin sulfide can provide Wp cost lower as compared to copper zinc tin sulfide.
Copper manganese tin sulfide that crystalizes into a stannite structure exhibits direct band gap and high absorption coefficient all of which are necessary for photovoltaic applications. Several studies on copper manganese tin sulfide have been mainly based on single crystals and nanocrystals. However, recent studies have been reported on copper manganese tin sulfide thin films for photovoltaic applications.
Alessia Le Donne, Maurizio Acciarri and Simona Binetti at University of Milano-Bicocca in collaboration with Stefano Marchionna and Federico Cernuschi at RSE SpA grew copper manganese tin sulfide thin films through a two-step vacuum process. They grew metal precursor stacks through thermal evaporation and then heat treated them in elemental sulfur vapors. Their research work is published in Solar Energy.
The authors settled for Cu-poor/Mn-rich copper manganese tin sulfide films with Mn/Sn ratio of 1 in a bid to avoid the development of insulating and highly conductive secondary phases. The researchers tested the proposed copper manganese tin sulfide thin films by photoluminescence, Raman, Scanning Electron Microscopy and Energy Dispersive Spectroscopy.
The research team were able to obtain Cu-poor/Mn-rich copper manganese tin sulfide specimens with an acceptable homogeneity of the metal compositional ratios through a stringent control of the manganese evaporation rate. Solar cells manufactured from the films indicated good performance as opposed to a previous study. In view of the advantages of low temperature post-deposition annealing in inert and air atmosphere reported in the literature, the authors investigated the impact of thermal treatments they did between 200 and 275 °C on the copper manganese tin sulfide solar cell efficiency. The analysis encompassed both modification of material attributes and electrical performance.
The best annealing at 225 °C in air for about 40 minutes allowed for significant enhancement of their performance, open circuit voltage 354 mV, short circuit current density 5.8 mA/cm2, 40% fill factor and efficiency of 0.83%. This therefore increased the efficiency of this promising material.
About The Author
Alessia Le Donne got a M.S. degree in Materials Science from the University of Milano-Bicocca in 2001 and in 2004 a Ph.D. in Materials Science from the same Institution. Since 2005 she got several postdoctoral fellowships at the University of Milano-Bicocca and a research fellowship at CNISM (National Interuniversity Consortium for the Physical Sciences of Matter).
She co-authored 63 peer-reviewed papers, 1 book chapter and more than 80 contributions at national or international scientific conferences. Since 2001 she has been involved in several European and national Projects. She regularly serves as peer-reviewer for high impact factor international scientific journals. She is associated editor of the international journals ‘Reviews in Advanced Sciences and Engineering’ and ‘Materials Focus’ and member of the editorial board of ‘Conference Papers in Energy’ and ‘Indian Journal of Materials Science’.
About The Author
Stefano Marchionna got a M.S. degree with honours in Materials Science from the University of Milano-Bicocca in 2003 and a Ph.D. in Materials Science from the same University in 2006. He co-authored 20 peer-reviewed papers and more than 30 communications at national or international scientific conferences. In 2007, he was process engineer at NED Silicon Company (Italy), working on the development of an innovative production line for solar grade silicon. From 2008 to 2013, he was process engineer at Voltasolar Company (Italy), working on the development of low-cost thin films solar cells based on Cu(In,Ga)Se2 (CIGS). Presently, his research activity at RSE SpA (Italy) is focused on the development of new and alternative materials based on Earth abundant elements both for photovoltaic and energy storage applications.
About The Author
Maurizio Acciarri is Associate Professor in Physics at the Department of Materials Science of the University of Milano-Bicocca. His research activity is mainly addressed to the study of electrical properties of semiconductors for photovoltaic applications. His research in the field of thin films for photovoltaic applications led to an international patent and to the technological transfer of the related Cu(In, Ga)Se2 growth process to a pilot line. He is co-author of 4 patents. From 2017 he is Director of the Management Committee of the Microscopy Platform of the University of Milano-Bicocca.
Since 2011 he is member of the scientific committee of the Milano-Bicocca Solar Energy Research Center (MIBSOLAR) and since 2013 he is co-director of the center. Since 2014 he is member of the scientific committee and teacher of the Green Energy Management Summer School. Since 2017 he is member of the scientific committee and teacher for the PhD school in Sustainable Human Development. Since 2017 he is member of the editorial board of the international journal ‛Solar Energy’.
About The Author
Federico Cernuschi is the head of the Materials for Energy Research Group at RSE SpA. After completing his studies in physics at the University of Milan, since 1990 he worked on the development and application of advanced non-destructive techniques for the integrity assessment of power plant components and for the physical, thermophysical characterization and wear resistance of coatings and materials for energy applications. He has been responsible for several EU funded research projects. He has published more than 60 papers in international scientific journals. He sits on national and international standards committees focusing on wear and NDE&T and advanced ceramics.
About The Author
Simona Binetti is Associated Professor of Physical Chemistry at University of Milano-Bicocca, vice director of Milano-Bicocca Solar Energy Research Center (MIBSOLAR), representing UNIMIB in the Joint Program on Photovoltaics of European Energy Research Alliance. Qualified Full Professor in Physical Chemistry. Graduated in Physics, Master in Materials Science and PhD in Chemistry.
Recognized expert in effect of defects on optoelectronic properties of silicon based semiconductors. Involved in 10 European Projects, 9 national about PV, some of them as leader, collaborating in research for private owned companies. She is currently leading 3 projects. Co-author of 120 peer-reviewed publications, 4 book chapters, 4 patents.
Reference
A. Le Donne, S. Marchionna, M. Acciarri, F. Cernuschi, S. Binetti. Relevant efficiency enhancement of emerging Cu2MnSnS4 thin film solar cells by low temperature annealing. Solar Energy, volume 149 (2017), pages 125–131.
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