Emission Mechanism of Self-Trapped Excitons in Sb-Doped All-Inorganic Metal-Halide Perovskites.

Sb doping confers highly efficient and color-diverse broadband light emission to all-inorganic metal-halide perovskites. However, the emission mechanism is still under debate. Herein, a trace amount of Sb ions (<0.1% atomic percentage) doping in the typical all-inorganic perovskites CsNaInCl, RbInCl, and CsInCl·HO allows universal observation of the fine structure in the photoluminescence excitation spectrum of the electron. A lifetime mapping method was utilized to reveal the origin of broadband emission triggered by Sb doping, by which various fluorescence components can be differentiated. In particular, free-exciton emission was identified at the high-energy end of the broadband emission for all three doped systems. The excitation-energy- and temperature-dependent fluorescence decay further indicates the existence and origin of self-trapped states. The observed structural and vibrational symmetry-dependent emission behaviors suggest dipole interactions can dramatically alter Stokes-shift energy and modulate the light-emitting wavelength.