Engineering of Perovskite Materials Based on Formamidinium and Cesium Hybridization for High-Efficiency Solar Cells
Daniel Prochowicz, Rashmi Runjhun, Mohammad Mahdi Tavakoli, Pankaj Yadav, Marcin Saski, Anwar Q. Alanazi, Dominik J. Kubicki, Zbigniew Kaszkur, Shaik M. Zakeeruddin, Janusz Lewinski, and Michael Grätzel
Chem. Mater. (2019) 31, 1620−1627
Engineering the chemical composition of inorganic-organic hybrid perovskite materials is an effective strategy to boost the performance and operational stability of perovskite solar cells (PSCs). Among the diverse family of ABX3 perovskites, methylammonium-free mixed A-site cation CsxFA1‐xPbI3 perovskites appear as attractive light absorber materials due to their optimum bandgap, superior optoelectronic property, and good thermal stability. Here,we develop a simple and very effective one-step solution method for the preparation of high-quality (Cs)x(FA)1-xPbI3 perovskite films upon the addition of excess CsCl to the FAPbI3 precursor solution. It is found that the addition of CsCl as a source of Cs cation instead of relevant addition of CsI to the parent perovskite solution increases effectively the grain size and film quality leading to improved charge mobility, reduced carrier recombination and long carrier life time. The resultant mesoscopic perovskite devices exhibit a maximum efficiency of 20.60% with a stabilized PCE of 19.85% and lower hysteresis compared to the reference device. This performance is among of the highest reported for PSC devices incorporating mixed cation (Cs)x(FA)1-xPbI3 perovskites.