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

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 CsPbIBr 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 into the CsPbIBr 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 Pb and PEG to passivate the defects in the CsPbIBr perovskite, which leads to large suppression of noise current. Both specific detectivity and linear dynamic range improved from 4.1 × 10 Jones and 73 dB to 2.2 × 10 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.