Mn²⁺-Doped CsPbBr₂I Quantum Dots Photosensitive Films for High-Performance Photodetectors

The variable bandgap and high absorption coefficient of all-inorganic halide perovskite quantum dots (QDs), particularly CsPbBr₂I make them highly promising for photodetector applications. However, their high defect density and poor stability limit their performance. To overcome these problems, Mn²⁺-doped CsPbBr₂I QDs with varying concentrations were synthesized via the one-pot method in this work. By replacing Pb²⁺ ions, moderate Mn²⁺ doping caused lattice contraction and improved crystallinity. At the same time, Mn²⁺-doping effectively passivated surface defects, reducing the defect density by 33%, and suppressed non-radiative recombination, thereby improving photoluminescence (PL) intensity and carrier mobility. The optimized Mn:CsPbBr₂I QDs-based photodetector exhibited superior performance, with a dark current of 1.19 × 10^-10 A, a photocurrent of 1.29 × 10^-5 A, a responsivity (R) of 0.83 A/W, a specific detectivity (D*) of 3.91 × 10¹² Jones, an on/off ratio up to 10⁵, and the response time reduced to less than 10 ms, all outperforming undoped CsPbBr₂I QDs devices. Stability tests demonstrated enhanced durability, retaining 80% of the initial photocurrent after 200 s of cycling (compared to 50% for undoped devices) and stable operation over 20 days. This work offers a workable strategy for rational doping and structural optimization in the construction of high-performance perovskite optoelectronic devices.