One-Center and Two-Center Self-Trapped Excitons in Zero-Dimensional Hybrid Copper Halides: Tricolor Luminescence with High Quantum Yields
Xiaoyu Liu, Yuanyuan Li, Tianyuan Liang, Wenjie Liu, Jiyang Fan
Abstract
The organic–inorganic hybrid copper halides exhibit intriguing and complex photophysical properties, and the underlying mechanisms are far from clear. Here, we study the photodynamics of six novel types of low-dimensional hybrid copper halides, which have a maximum quantum yield of 98.6%. They exhibit two origins of photon emission with distinct temperature dependence and quantum transition rates. The experiments in junction with first-principles calculations indicate that they stem from two kinds of self-trapped excitons (STEs): one-center a-STE (localized on Cu+ monomer) and two-center m-STE (localized on Cu22+ dimer). There is phase transition between a-STE and m-STE when enough thermal energy is acquired for crossing the potential barrier between them. The degree of softness of the compositional organic cations of the copper halide plays a key role in determining the self-trapping type of the STEs.