High Efficiency Organic/Inorganic Hybrid Planar MAPbI3 Based Perovskite Solar Cells via Zwitterion Additives

Abstract

Organic-inorganic hybrid perovskite solar cells are one of the most prominent photovoltaic technologies. Among perovskite materials, methylammonium lead iodide perovskite, as CH3NH3PbI3 is the most studied one. However, there is still challenging issues related to efficiency, stability, and scalability of perovskite solar cell. In our research, we have demonstrated a concept of the amino acid derivative as an additive for fabricating air-stable perovskite solar cells that exhibits exceptional solar-to-electric power conversion efficiencies by simple treatment. The amino acid is a material with amine and carboxylic acid functional groups. These functional groups can be changed primary ammonium ion (cation) and carboxylate (anion) depending on pH. The carboxylate acting as a Lewis base served to reduce the trap site of CH3NH3PbI3 and also to increase the grain size. The primary ammonium salt has an effect of increasing stability by their own hygroscopic properties and inhibition of ion-migration in perovskite material. In this work, we used alanine, which is a kind of amino acid and zwitterion in the neutral condition, and achieve highly efficient (20%) and air-stable (2500h) planar type perovskite solar cells.