Influence of surface groups on SnO2 nanoparticles in enhancing perovskite photodetector performance

Abstract

Tin oxide (SnO₂) has been extensively investigated as an electron-conductive material in perovskite solar cells. Over several years, various research efforts have reported different synthesis methods and modification strategies to improve power conversion efficiency (PCE). The PCE of 25.5% has been achieved by coupling Cl-bonded SnO₂ with a Cl-containing perovskite precursor. Despite numerous studies on the influence of surface groups on SnO₂, few have focused on their role in perovskite photodetectors (PPDs). In this study, we used the SnO₂ nanoparticle layer as a modification layer for indium tin oxide (ITO), achieving PPDs with low dark current and high detectivity (up to 10¹³ Jones). The devices with the SnO₂ layer annealed at different temperatures were fabricated for comparison. Characterizations such as scanning electron microscope (SEM), ultraviolet photoelectron spectroscopy (UPS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were performed to elucidate the role of surface groups in modifying the work function and inhibiting of leakage current. The results suggest that chemically absorbed H₂O or OH groups on the SnO₂ surface play a crucial role in reducing the dark current and affecting perovskite crystallization. Additionally, Sn⁴⁺ coupling with OH- or H₂O may influence the Fermi level of modified ITO.