Quantifying Stabilized Phase Purity in Formamidinium-Based Multiple-Cation Hybrid Perovskites

• DOI: 10.1021/acs.chemmater.0c04185
• Publication Date: 2021-04-16T14:27:58Z
• Authors: Lena Merten; Alexander Hinderh...; Thomas Baumeler; Neha Arora; Jan Hagenlocher; Shaik Mohammed Za...; M. Ibrahim Dar; Michael Grätzel; Frank Schreiber
• Keywords: Formamidinium; Rubidium; Caesium; Hexagonal phase

A promising approach for the production of highly efficient and stable hybrid perovskite solar cells is employing mixed-ion materials. Remarkable performances have been reached by materials comprising a stabilized mixture methylammonium (MA+) formamidinium (FA+) as monovalent cation. We compare quantify methods stabilizing FA-based perovskites involving additional blending smaller inorganic cations cesium (Cs+) rubidium (Rb+), which can lead to an improvement in phase purity black cubic modification. Even under excess iodide conditions, presence separate PbI2 well hexagonal phases, are very common formamidinium-containing perovskites, be drastically reduced or even completely prevented. In this aspect, adding both Cs+ Rb+ showed greater effectivity than only Cs+, enabling increase percentage within material from 45% double-cation FA:MA 97.8% quadruple composition. The impact admixing on crystal structure resulted enlarged homogeneous crystallite sizes less pronounced orientational order indicated also minor modifications unit cell sizes. Finally, we discuss charge-carrier recombination dynamics performance.