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 Pb2+ in BDAPbI(4) with an M-I(+) (Na+, K+, Rb+, Cu+, Ag+, and Au+) and M-III(3+) (Bi3+, In3+, and Sb3+) 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.