A-Site Cation Engineering of CsPbBr3 Nanocrystals: Correlating Lattice Microstrain, Optical Properties, and Photodetector Performance

Abstract All-inorganic cesium lead bromide (CsPbBr3) nanocrystals (NCs) have recently attracted extensive attention due to their high photoluminescence quantum yield (PLQY), tunable bandgap, and promising applications in photodetectors. However, the stability of photodetector devices is still limited by the defect states, lattice microstrain, and phase instability. In this work, we investigate the effects of A-site cation doping (K+, Rb+, and FA+) on the structural, optical, and photodetection properties of CsPbBr3 NCs, leading to stable photodetectors. By combining the Williamson–Hall method and DFT calculations, it has been confirmed that moderate A-site doping can preserve the cubic perovskite phase while inducing slight lattice contraction, reducing dislocation density, and enhancing crystallinity. As a result, the microstrain of 5% Rb+-doped (nominal precursor concentrations) CsPbBr3 lattice is stable around 0.0028, while its PLQY increases to 98.7% (solution) and the slow-decay lifetime extends to 81.65 ns. The photodetector devices based on doped CsPbBr3 NCs exhibit enhanced responsivity around 6.99 A/W at a high incident power of 28.1 mW, and the detectivity is stabilized around 4.9 × 1010 Jones at the light intensity from 5.6 to 22.5 mW. These findings provide clear evidence that rational A-site cation engineering is an effective strategy to optimize the optoelectronic performance of CsPbBr3 NCs for high-performance photodetectors.