Modulating the Photocarrier Dynamics in CsPbBr3 Quantum Dots via Cu2+ Doping for Enhanced Photoelectrochemical Performance

Abstract Lead halide perovskite quantum dots (PQDs) have emerged as promising materials for next-generation optoelectronic and photoelectrochemical devices owing to their high absorption coefficients, tunable bandgaps, and solution processability. Among them, CsPbBr3 exhibits superior structural stability and optoelectronic performance; however, its practical implementation in photovoltaic and photoelectrochemical systems is fundamentally bottlenecked by sluggish charge carrier kinetics. Here, we overcome this limitation by engineering the electronic landscape of CsPbBr3 PQDs through strategic Cu2+ cation doping. Structural analysis via X-ray diffraction confirms a systematic lattice contraction, evidenced by a progressive shift of diffraction peaks toward higher 2θ values, resulting from the incorporation of the smaller Cu2+ radius. This structural modulation induces a hypsochromic shift in both absorption and emission profiles, signifying a dopant-dependent widening of the optical bandgap. Notably, we observe a significant quenching of photoluminescence intensity, which coupled with a marked reduction in charge-transfer resistance in Nyquist plots, identifying a transition from radiative recombination to improved charge separation. Most importantly, transient photocurrent measurements demonstrate a two-fold enhancement in photocurrent density compared to pristine CsPbBr3 PQDs. We attribute this improvement to lattice contraction, potentially associated with Jahn–Teller effects of Cu2+, which facilitates charge carrier mobility and interfacial charge extraction. These findings establish Cu2+ doping as an effective strategy to engineer the electronic structure and charge transport properties of CsPbBr3 PQDs, advancing their potential for high-performance, solution-processed photoelectrochemical and photovoltaic applications.