Efficient AgBiS2 Nanocrystal Solar Cells enabled by Cation Disorder Engineering
Yongjie Wang a, Sean Kavanagh b c, Ignasi Burgués-Ceballos a, Aron Walsh c d, David Scanlon b, Gerasimos Konstantatos a e
a ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
b Thomas Young Centre and Department of Chemistry, University College London, London, United Kingdom.
c Thomas Young Centre and Department of Materials, Imperial College London, London, United Kingdom.
d Department of Materials Science and Engineering, Yonsei University, Seoul, Korea (the Republic of).
e ICREA-Institució Catalana de Recerca i Estudia Avançats, Lluis Companys 23, Barcelona, Spain.
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Yongjie Wang, presentation 119
DOI: https://doi.org/10.29363/nanoge.hopv.2022.119
Publication date: 20th April 2022

Strong optical absorption of a semiconductor is a highly desirable property for a material to be considered in optoelectronic and photovoltaic applications. Strong light absorbers can enable ultrathin solar cells and photodetectors that in turn lead to significant reductions in cost, weight and manufacturing throughput as well as improve quantum efficiency and performance. The optimal thickness of a semiconductor absorber is primarily determined by its absorption coefficient. To date, this parameter has been considered as a fundamental material property and efforts to realize thinner photovoltaics have relied on light-trapping structures that add complexity and cost. Here, we demonstrate that by engineering cation disorder homogeneity in a ternary chalcogenide semiconductor leads to significant absorption increase due to enhancement of the optical transition matrix elements. We show that cation disorder engineered AgBiS2 colloidal nanocrystals offer an absorption coefficient that is higher than any other photovoltaic material used to date, enabling highly efficient extremely thin absorber (ETA) photovoltaic devices. Leveraging this high absorption and by further optimization of the electron and hole blocking layers we report solution-processed, environmentally-friendly, 30nm thick ETA solar cells with short circuit current density of 27 mA/cm2, a record power conversion efficiency of 9.17% (8.85% certified) and high stability under ambient conditions. Our work not only establishes the extraordinary potential of ultrathin AgBiS2 NC solar cells, which are solutionprocessable and RoHS-compliant, but also demonstrates the importance and power of atomic configuration engineering in multinary systems.

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