17.78% efficient low-temperature carbon-based planar perovskite solar cells using Zn-doped SnO2 electron transport layer

Abstract

Organic-inorganic lead halide perovskite solar cells have garnered enormous interest in scientific communities due to comparable power conversion efficiencies and solution-processed fabrication techniques. Among them, carbon-based perovskite solar cells seem to be one of the most promising candidates for addressing the stability issue while suffering from inferior efficiency or high processing temperature. Herein, we introduce low-temperature processed Zn-doped SnO2 (below 200 °C) as an effective electron transport layer in perovskite solar cells for the first time, and demonstrate a low-temperature carbon-based device with Cu-phthalocyanine as hole transport layer. We find that Zn doping contributes to a more suitable energy level alignment and an improved conductivity for SnO2 films. As a result, the electron transfer and extraction are enhanced and the charge recombination is suppressed. In addition, devices with Zn-doped SnO2 have a wider depletion region, leading to an enhanced photovoltaic performance. An optimal efficiency of 17.78% can be obtained after 2 mM Zn doping. Furthermore, these devices, introducing highly stable and hydrophobic Cu-phthalocyanine and carbon, maintain almost 100% of their initial efficiencies over 1200 h in ambient air. Our study paves the way for developing highly efficient and flexible carbon-based perovskite solar cells.