Coupling Electronic Structure Modulation with Self-Trapped Exciton Dynamics in Dual-Doped Cs3Bi2Br9 for Efficient...

Area of Science:

• Materials Science
• Photocatalysis
• Solid-State Chemistry

Background:

• Lead-free halide perovskites offer low toxicity and tunable properties for optoelectronics.
• Challenges include poor stability and limited understanding of excited-state regulation.
• Developing stable, efficient lead-free perovskites is crucial for sustainable energy applications.

Purpose of the Study:

• To enhance the stability and photocatalytic hydrogen evolution of Cs3Bi2Br9 using a synergistic Rb+/Sb3+ codoping strategy.
• To investigate the effects of codoping on crystal structure, excited-state dynamics, and carrier utilization.
• To establish a structure-excited state-function relationship for optimizing lead-free perovskite photocatalysts.

Main Methods:

• Synthesis of Cs3Bi2Br9:x%Rb+,25%Sb3+ microcrystals with varying Rb+ concentrations.
• Structural characterization using X-ray diffraction and other techniques.
• Spectroscopic analysis, including femtosecond transient absorption (fs-TA), to study excited-state evolution and carrier dynamics.

Main Results:

• Codoping with Rb+ and Sb3+ resulted in a more stable Cs3Bi2Br9 perovskite structure.
• Sb3+ enhanced electron-phonon coupling and self-trapped exciton (STE) formation.
• Rb+ modified STE relaxation dynamics, suppressed radiative recombination, and improved carrier utilization.
• Femtosecond transient absorption revealed controlled excited-state evolution and enhanced charge transfer.
• Achieved a 5.8-fold increase in hydrogen evolution rate (144 μmol·g-1 h-1) compared to pristine Cs3Bi2Br9.
• Pt co-catalysis further boosted the rate to 393 μmol·g-1 h-1 by accelerating charge separation and proton reduction.

Conclusions:

• Synergistic Rb+/Sb3+ codoping effectively enhances the stability and photocatalytic activity of Cs3Bi2Br9.
• Exciton engineering via codoping is a viable strategy to optimize lead-free perovskites for hydrogen evolution.
• The study establishes a valuable structure-excited state-function relationship for designing advanced photocatalysts.