Ultrafast Dynamics Across Pressure‐Induced Electronic State Transitions, Fluorescence Quenching, and Bandgap Evolution in CsPbBr₃ Quantum Dots

Abstract

This work investigates the impact of pressure on the structural, optical properties, and electronic structure of CsPbBr3 quantum dots (QDs) using steady‐state photoluminescence, steady‐state absorption, and femtosecond transient absorption spectroscopy, reaching a maximum pressure of 3.38 GPa. The experimental results indicate that CsPbBr3 QDs undergo electronic state (ES) transitions from ES‐I to ES‐II and ES‐II to ES‐III at 0.38 and 1.08 GPa, respectively. Intriguingly, a mixed state of ES‐II and ES‐III is observed within the pressure range of 1.08–1.68 GPa. The pressure‐induced fluorescence quenching in ES‐II is attributed to enhanced defect trapping and reduced radiative recombination. Above 1.68 GPa, fluorescence vanishes entirely, attributed to the complete phase transformation from ES‐II to ES‐III in which radiative recombination becomes non‐existent. Notably, owing to stronger quantum confinement effects, CsPbBr3 QDs exhibit an impressive bandgap tuning range of 0.497 eV from 0 to 2.08 GPa, outperforming nanocrystals by 1.4 times and bulk counterparts by 11.3 times. Furthermore, this work analyzes various carrier dynamics processes in the pressure‐induced bandgap evolution and electron state transitions, and systematically studies the microphysical mechanisms of optical properties in CsPbBr3 QDs under pressure, offering insights for optimizing optical properties and designing novel materials.

Pressure-Induced Changes in the Phase Distribution and Carrier Dynamics of Quasi-Two-Dimensional Ruddlesden–Popper Perovskites

“…From Figure S12a, τ 1 increases as the pressure increases from 1 atm to 0.49 GPa. This is because the Pb–Br bond lengths decrease under pressure, and the resulting repulsive force causes the lattice hardening, , making it difficult for hot charge carriers to cool through interaction with the lattice. In the pressure range of 0.49–4.06 GPa, the τ 1 lifetime decreases continuously with an increase in pressure.…”