Defect Passivation via Additive Engineering to Improve Photodetection Performance in CsPbI₂Br Perovskite...

Solution-processable all-inorganic lead halide perovskites are under intensive attention due to their potential applications in low-cost high-performance optoelectronic devices such as photodetectors. However, solution processing usually generates structural and chemical defects which are detrimental to the photodetection performance of photodetectors. Here, a polymer additive of polyethylene glycol (PEG) was employed to passivate the localized defects in CsPbI₂Br films through the Lewis acid-base interaction. The interfacial defects were passivated efficiently by introducing a trace amount of a PEG additive with a concentration of 0.4 mg mL^-1 into the CsPbI₂Br precursor solution, as suggested by the significantly reduced trap density of state, which was revealed using thermal admittance spectroscopy. Fourier transform infrared spectrum characterization showed that rather than Cs⁺ or I^-, a Lewis acid-base interaction was established between Pb²⁺ and PEG to passivate the defects in the CsPbI₂Br perovskite, which leads to large suppression of noise current. Both specific detectivity and linear dynamic range improved from 4.1 × 10⁹ Jones and 73 dB to 2.2 × 10¹¹ Jones and 116 dB, respectively. Our work demonstrates the feasibility of employing an environmentally stable polymeric additive PEG to passivate defects for high photodetection performance in all-inorganic perovskite photodetectors.