Complex compositional engineering of mixed halides/mixed cations perovskites has recently fostered a rapid progress in perovskite solar cell technol. Here we demonstrate that when 10% of formamidinium (FA+) is simply added into methylammonium lead iodide (MAPbI3) a highly cryst. and compositionally uniform perovskite is formed, self-organizing into a stable "quasi-cubic" phase at room temp. We reached power conversion efficiency of over 20.2%, the highest value reported to date for FAxMA1-xPbI3 perovskite.
Mohammad Khaja Nazeeruddin, Sanghyun Paek, Yonghui Lee, Kyung Taek Cho