We demonstrate four and two-terminal perovskite-perovskite tandem solar cells with ideally matched bandgaps. We develop an infrared absorbing 1.2eV bandgap perovskite, FA0.75Cs0.25Sn0.5Pb0.5I3, that can deliver 14.8 % efficiency. By combining this material with a wider bandgap FA0.83Cs0.17Pb(I0.5Br0.5)3 material, we reach monolithic two terminal tandem efficiencies of 17.0 % with over 1.65 volts open-circuit voltage. We also make mechanically stacked four terminal tandem cells and obtain 20.3 % efficiency. Crucially, we find that our infrared absorbing perovskite cells exhibit excellent thermal and atmospheric stability, unprecedented for Sn based perovskites. This device architecture and materials set will enable 'all perovskite' thin film solar cells to reach the highest efficiencies in the long term at the lowest costs.
@article{arxiv.1608.03920,
title = {Perovskite-perovskite tandem photovoltaics with optimized bandgaps},
author = {Giles E. Eperon and Tomas Leijtens and Kevin A. Bush and Rohit Prasanna and Thomas Green and Jacob Tse-Wei Wang and David P. McMeekin and George Volonakis and Rebecca L. Milot and Richard May and Axel Palmstrom and Daniel J. Slotcavage and Rebecca A. Belisle and Jay B. Patel and Elizabeth S. Parrott and Rebecca J. Sutton and Wen Ma and Farhad Moghadam and Bert Conings and Aslihan Babayigit and Hans-Gerd Boyen and Stacey Bent and Feliciano Giustino and Laura M. Herz and Michael B. Johnston and Michael D. McGehee and Henry J. Snaith},
journal= {arXiv preprint arXiv:1608.03920},
year = {2017}
}