Enhancing the efficiency of perovskite solar cells using mesoscopic zinc-doped TiO2 as the electron extraction layer through band alignment

Abstract

Lead halide perovskite-structured solar cells (PSCs) have drawn great attention due to a rapid improvement in their photoelectric conversion efficiency in recent years. In this study, we have enhanced photovoltaic performance by using mesoscopic zinc-doped TiO₂ (meso-Zn:TiO₂) as the electron extraction layer. Zn:TiO₂ nanoparticles (Zn:TiO₂ NPs) with various zinc doping levels were synthesized by combining sol–gel and hydrothermal methods. The synthesized Zn:TiO₂ NPs were used to fabricate electron extraction layers by a screen-printing method. We systematically investigated the surface morphology, crystal structure, contact angle, charge carrier dynamics, electron mobility, and electrical conductivity of various meso-Zn:TiO₂. Furthermore, photo-assisted Kelvin probe force microscopy (KPFM) was used to analyze the surface potential of perovskite films coated with various meso-Zn:TiO₂ to understand the electron extraction behavior under the illumination of light at various wavelengths. Moreover, the energy levels of various meso-Zn:TiO₂ were estimated by ultraviolet photoelectron spectroscopy (UPS) and UV-vis absorption spectroscopy. We discovered that the 5.0 mol% meso-Zn:TiO₂ exhibited the optimal band alignment with perovskite. Finally, the average power conversion efficiency (PCE) of PSCs with meso-Zn:TiO₂ was enhanced from 13.1 to 16.8%, and such fabricated PSC yielded a champion PCE of 18.3%.