Progress of Pb‐Sn Mixed Perovskites for Photovoltaics: A Review
R. M. I. Bandara, Shashini M. Silva, Cameron C. L. Underwood, K. D. G. Imalka Jayawardena, Radu A. Sporea, S. Ravi P. Silva
Abstract
Pb‐Sn mixed perovskites are becoming increasingly popular as narrow‐bandgap (1.2–1.3 eV) light absorbers in single‐junction perovskite solar cells (PSCs) and as bottom cells for all‐perovskite tandem solar cells, for high‐efficiency, low‐cost, lightweight, roll‐to‐roll printable photovoltaic (PV) applications. From the first report of planar Pb:Sn mixed PSCs in 2014, the power conversion efficiencies (PCE) have increased from 10% to 21% by the end of 2020 with an exponential growth in research conducted in this field. Despite much effort, the performance and stability of Pb‐Sn mixed PSCs are still limited, which constrains their long‐term use in all‐perovskite tandem devices. This review highlights the avenues explored in improving different aspects of Pb‐Sn mixed PSCs and provides a comprehensive discussion of the interdependent factors affecting the device performance. This includes compositional engineering of the perovskite crystal, absorber layer fabrication and crystallization methods, bandgap tuning, Sn 4+ reduction, and surface passivation of the absorber layer, as well as the selection of interlayers and electrodes of the final PSC.