Tuning the optical absorption and emission of vacancy-ordered double perovskites

Abstract

Vacancy-ordered double perovskites of the formula A2MX6 (where A is a +1 cation, M is a +4 metal, and X is a halide ion) offer improved ambient stability over other AMX3 perovskites and reduced toxicity compared to those containing lead. Furthermore, their broad, highly Stokes-shifted emission makes them particularly well-suited for single-component white light generation. However, the mechanism behind this emission is poorly understood. To address this gap, we have synthesized a series of perovskites with both inorganic and organic A-site cations of varying sizes to demonstrate how the cation identity impacts the Stokes shift, quantum yield, and emission lifetime. We have also investigated the effect that the metal halide precursor and solvent system have on the optical absorption and defect density in these systems, dramatically affecting their emission lifetimes. Overall, our work highlights how structural changes in both composition and defect density can impact optical properties such as absorption edge, quantum yield, and emission lifetime, and sheds light on how the optical properties of these semiconductors can be controlled for light-emitting applications.