Improving Lattice Rigidity and Charge Carrier Lifetime by Engineering Spacer Cation of Ruddlesden-Popper Perovskites: A Time-Domain Ab Initio Study.

First-principles quantum dynamics calculations show that charge carrier lifetimes, charge transport, and lattice stability are notably improved when BA (CH 3 (CH 2 ) 3 NH 3 + ) in BA 2 PbI 4 is replaced with MTEA (CH 3 (CH 2 ) 2 SNH 3 + ). By suppressing atomic fluctuations, MTEA enhances the lattice stiffness and inhibits loss of coherence due to the S-S interaction. By delocalizing hole wave functions on the MTEA, particularly on the S atoms, while maintaining the electron wave functions largely unchanged compared to the BA 2 PbI 4 , MTEA serves to enhance charge transport and NA coupling while narrowing the bandgap by 0.18 eV. Overall, MTEA decreases NA coupling due to slow atomic motions against a large overlap of electron-hole wave functions, which suppresses nonradiative electron-hole recombination and prolongs carrier lifetime twice longer compared with BA 2 PbI 4 . This simulation presents a rational route to make high performance two-dimensional perovskite solar cells.