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 Ai with large steric hindrance, which determine the structural distortion of the perovskite. The higher proportion of Ai 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.