Novel Combination of Efficient Perovskite Solar Cells with Low Temperature Processed Compact TiO₂ Layer via Anodic Oxidation

Abstract

In this work, a facile and low temperature processed anodic oxidation approach is proposed for fabricating compact and homogeneous titanium dioxide film (AO-TiO₂). In order to realize morphology and thickness control of AO-TiO₂, the theory concerning anodic oxidation (AO) is unveiled and the influence of relevant parameters during the process of AO such as electrolyte ingredient and oxidation voltage on AO-TiO₂ formation is observed as well. Meanwhile, we demonstrate that the planar perovskite solar cells (p-PSCs) fabricated in ambient air and utilizing optimized AO-TiO₂ as electron transport layer (ETL) can deliver repeatable power conversion efficiency (PCE) over 13%, which possess superior open-circuit voltage (Voc) and higher fill factor (FF) compared to its counterpart utilizing conventional high temperature processed compact TiO₂ (c-TiO₂) as ETL. Through a further comparative study, it is indicated that the improvement of device performance should be attributed to more effective electron collection from perovskite layer to AO-TiO₂ and the decrease of device series resistance. Furthermore, hysteresis effect about current density–voltage (<i>J</i>–<i>V</i>) curves in TiO₂-based p-PSCs is also unveiled