Giant Band-Gap Renormalization and Morphology-Tunable Defect-Assisted Carrier Recombination in CsPbBr3 Microstructures

Inorganic halide perovskite microstructures have presented intriguing potential for the development of high-performance optoelectronic devices. To advance the application of inorganic halide perovskite microstructures, it is crucial to understand the correlation between their morphologies and the dynamic properties of carriers. In this work, we investigated the carrier dynamics in CsPbBr3 microrods and microplates primarily by using femtosecond transient absorption spectroscopy. Our results reveal a giant band-gap renormalization (BGR) effect originated from Coulombic enhancement, resulting in transient band-gap shrinkages as large as 480 and 336 meV for CsPbBr3 microrods and microplates, respectively. The photoexcited carriers in both microstructures undergo four dynamic processes: thermalization and cooling, BGR, defect-assisted recombination, and Auger recombination. A proposed phenomenological model can be used to well analyze the dynamics and identify different time constants. The time constants for BGR are strongly dependent on pump fluence and probe wavelength, whereas the defect-assisted recombination time shows opposite fluence dependences in CsPbBr3 microplates and microrods, respectively, due to the difference in defect densities between the two CsPbBr3 microstructures. These findings provide new insights into the morphology-related carrier dynamics, particularly the many-body interactions in CsPbBr3 microstructures, which offer potential applications in optoelectronic and photonic devices that benefit from their microstructure dimensions.