Lead-free germanium iodide perovskite materials for photovoltaic applications

Abstract

Computational screening based on density-functional-theory calculations reveals Ge as a candidate element for replacing Pb in halide perovskite compounds suitable for light harvesting. Experimentally, three AGeI₃ (A = Cs, CH₃NH₃ or HC(NH₂)₂) halide perovskite materials have been synthesized. These compounds are stable up to 150 °C, and have bandgaps correlated with the A-site cation size. CsGeI₃-based solar cells display higher photocurrents, of about 6 mA cm⁻², but are limited by poor film forming abilities and oxidising tendencies. The present results demonstrate the utility of combining computational screening and experimental efforts to develop lead-free halide perovskite compounds for photovoltaic applications.