Ligand-Dependent Performance Optimization of CsPbX3/N-Si Schottky Photodiodes for Broadband Photodetection

Abstract

All-inorganic cesium lead halide perovskite nanoparticles (CsPbX3, X = Cl, Br) are promising candidates for optoelectronic devices due to their high absorption coefficients, narrow emission linewidths, and superior thermal stability compared to hybrid perovskites. In this work, Schottky photodiodes were fabricated on n-type Si substrates using CsPbBr3 and CsPbCl3 nanoparticle interlayers, both with native oleylamine/oleic acid ligands and after pyridine-based ligand exchange. Structural and morphological analyses via AFM revealed that pyridine treatment improved surface uniformity for CsPbBr3 films but induced aggregation in CsPbCl3 films. Electrical characterization using thermionic emission theory, Cheung's method, and Norde's method showed composition- and ligand-dependent variations in barrier height, series resistance, and ideality factors. Under varying illumination intensities, pyridine-treated CsPbBr3 devices (D2) exhibited over tenfold improvements in responsivity and detectivity compared to their untreated counterparts (D1), while pyridine-treated CsPbCl3 devices (D4) demonstrated high performance at low light intensities and maintained strong broadband detection from 351-1600 nm. CsPbCl3 devices with native ligands (D3) displayed unstable performance, excelling only in the long-wavelength infrared region (> 1400 nm). These results highlight the critical role of surface chemistry in tailoring perovskite-silicon photodiodes for broadband photodetection applications.