Enhancing the performance of all vapor-deposited electron-conductor-free CsPbBr3 photodetectors via interface engineering for their applications in image sensing

Abstract

CsPbBr₃ photodetectors (PDs) are attracting tremendous attention for their superior properties, such as ultrafast light response and high chemical stability. However, the widely-used spin-coating technique involved in the preparation process of CsPbBr₃ PDs restricts the construction of large-scale PD arrays, making it challenging for their applications in high-resolution image sensing. Here, we demonstrate fully vapor-deposited CsPbBr₃ PDs with all the functional layers deposited through an evaporation route. The employment of an inexpensive copper(II) phthalocyanine (CuPc) hole conductor and the abandonment of the electron conductor can significantly decrease the whole production costs. An ultrathin MoO₃ buffer layer is further introduced to passivate the defect densities of the CsPbBr₃ perovskite and tailor the band alignment of the whole device. The reduced interface energy barrier and non-radiative recombination loss of the MoO₃-modified devices are revealed by both experimental characterization and theoretical density functional theory (DFT) analysis. The best-performing MoO₃-modified CsPbBr₃ PD achieves an ultrafast response time of 0.96 μs, an ultrahigh on/off ratio of 1.17 × 10⁶ and a detectivity of 5.22 × 10¹² Jones at 0 V bias voltage. This performance is one of the best among all the self-powered electron/hole-conductor-free perovskite PDs. A large-area (57.8 cm²) image sensor comprising 25 × 25 CsPbBr₃ PD arrays is further fabricated. Owing to the intrinsic advantages of the evaporation technique in depositing large-area and uniform films, the as-designed 625-pixel sensor exhibits a salient imaging capability. Our work opens up new avenues for the mass production of cost-effective, large-area and high-performing CsPbBr₃ PD arrays for applications in image sensing.