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 BDA 2 M I M III X 8 (BDA = 1,4-butanediamine) by substituting two Pb 2+ in BDAPbI 4 with an M I + (Na + , K + , Rb + , Cu + , Ag + , and Au + ) and M III 3+ (Bi 3+ , In 3+ , and Sb 3+ ) pair. First-principles calculations demonstrated the thermal stabilities of all the proposed BDA 2 M I M III X 8 perovskites. The electronic properties of BDA 2 M I M III X 8 depend strongly on the choice of M I + + M III 3+ 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 BDA 2 AuBiI 8 . 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.