A-Site Ion Doping in Cs2AgBiBr6 Double Perovskite Films for Improved Optical and Photodetector Performance

Perovskite materials, as emerging semiconductors, have attracted significant attention for their exceptional optoelectronic properties, tunable bandgaps, ease of fabrication, and cost-effectiveness, making them promising candidates for next-generation optoelectronic devices. The all-inorganic perovskite Cs2AgBiBr6 distinguishes itself from other perovskite materials due to its remarkable optical absorption and emission properties, excellent stability, prolonged carrier recombination lifetime, and nontoxic characteristics. However, a deeper understanding of its unique luminescent properties and a further optimization of its structure and performance are still necessary. This study systematically investigates the optimization of Cs2AgBiBr6 double perovskite films through A-site Na+ doping. At an optimal Na+ doping concentration of 3.5% (Na0.07Cs1.93AgBiBr6), the film shows 1.4 times and 2.7 times enhancement in light absorption and photoluminescence intensity, compared to the undoped film. Low-temperature spectroscopy measurements indicate that Na0.07Cs1.93AgBiBr6 exhibits higher exciton binding energy and phonon energy. Based on Na0.07Cs1.93AgBiBr6, the photodetectors demonstrate significant performance improvements, with a high photocurrent response of 10−2 A, a photo-to-dark current ratio (PDCR) of 7.57 × 104, a responsivity (R) of 16.23 A/W, a detectivity (D*) of 2.92 × 1012 Jones, a linear dynamic range (LDR) of 98.75 dB, and a fast response time of 943 ms. This work provides a promising strategy for optimizing all-inorganic perovskite materials through doping and offers guidance for enhancing high-performance photodetectors.