Modulating Carrier Dynamics in Halide Perovskites through Lattice Strain Engineering of CsPb_1–<i>x</i>Cu_<i>x</i>Br₃ for Improved Photocatalytic CO₂ Reduction

Developing strategies to optimize the reaction kinetics and promote the photocatalytic efficiency of metal halide perovskites represents a critical scientific challenge. The strain engineering emerges as an innovative approach to simultaneously regulate carrier dynamics and manipulate reaction intermediates/adsorbates via precise control of lattice distortion. Here, we synthesized a series of CsPb_1-<i>x</i>Cu_<i>x</i>Br₃ quantum dots (QDs) using a controlled hot-injection method. The ionic bonding characteristics and structural flexibility of CsPbBr₃ enable precise lattice strain engineering via B-site cation substitution. This approach effectively modulates the electronic band structure through controlled distortion of [PbBr₆]^4- octahedra. The geometric phase analysis of high-resolution transmission electron microscopy images has demonstrated that Cu²⁺ incorporation induces compressive strain within the perovskite lattice. Meanwhile, density functional theory (DFT) calculations have confirmed that the d-band center shifts upward from -3.05 to -2.09 eV in the compressive-strained CsPb_0.9Cu_0.1Br₃. Additionally, the fitting results of femtosecond transient absorption spectroscopy kinetics demonstrate that the shallow trap states formed by Cu-induced lattice distortion effectively steer photogenerated carriers toward interfacial redox processes, rather than bulk recombination. Consequently, it significantly enhances the separation of photogenerated electrons and holes, thereby optimizing the adsorption and desorption of key reaction intermediates during the CO₂ photocatalytic reduction process. This research reveals the impact of strain engineering on photocatalytic CO₂ reduction and provides theoretical guidance for designing high-performance photocatalytic materials.