Discovering Layered Lead-Free Perovskite Solar Absorbers Via Cation Transmutation

For the exploration of stable lead-free perovskites for solar cell applications, we propose a series of Dion-Jacobson (DJ) double perovskites with the formula BDA2MIMIIIX8 (BDA = 1,4-butanediamine) by substituting two Pb2+ in BDAPbI4 with an MI+ (Na+, K+, Rb+, Cu+, Ag+, and Au+) and MIII3+ (Bi3+, In3+, and Sb3+) pair. First-principles calculations demonstrated the thermal stabilities of all the proposed BDA2MIMIIIX8 perovskites. The electronic properties of BDA2MIMIIIX8 depend strongly on the choice of MI+ + MIII3+ and the structural archetype, and three out of 54 candidates with suitable solar band gaps and superior optoelectronic properties were selected for photovoltaic application. A highest theoretical maximal efficiency of over 31.6% is predicted for BDA2AuBiI8. The DJ-structure-induced interlayer interaction of apical I-I atoms is found to play a crucial role in promoting the optoelectronic performance of the selected candidates. This study provides a new concept for designing lead-free perovskites for efficient solar cells.