Alloying Engineering toward Tunable White Light-Emitting Perovskites

Recently, two-dimensional (2D) halide perovskites achieved impressive performance as broadband white-light emitters, which originate from exciton self-trapping in the distorted lattice. So far, it is still a challenge to modulate the exciton self-trapping process as well as tune the white light-emitting properties of 2D perovskites. Here we develop molecular alloying engineering to modulate the exciton self-trapping rate and depth in halide perovskites. We present a series of 2D perovskite alloys by incorporating molecules A with small steric hindrance and A_i with large steric hindrance, which determine the structural distortion of the perovskite. The higher proportion of A_i induces larger structural distortion of the perovskite and leads to a higher rate of exciton self-trapping and deeper exciton self-trapping depth. The designed perovskite alloys exhibit tunable broadband emission, covering from cool- to warm-white light. Our findings achieve exciton modulation and provide a general method for tailoring the optical properties of perovskites.