Enhanced ZnO-based ETL and nanostructured interface modification for improved perovskite solar cells efficiency

Abstract

Compared to standard silicon solar cells and other thin film cells, perovskite solar cells (PSCs) can achieve high power conversion efficiency and reduce the production costs. ZnO-based ETL in perovskite solar cells provides a lot of benefits, such as low processing temperature and high mobility. However, the reported instability of perovskite layers placed atop ZnO, resulting in poor device performance, has prevented it from being widely used in perovskite solar cells, though. In this work, an innovative way of insuring device performance and longer-term stability is proposed via the incorporation of a novel efficient process. Herein, a V-doped ZnO/Y-doped TiO2 electron transport bilayer was developed to combine the benefits of strong electron extraction and minimal interfacial recombination. This combined approach of engineering both the improved performance of VZnO as ETL and YTiO2 flower like structures at the interface ETL/Perovskite results in large improvements in the performance of the PSC. V-doped ZnO (VZnO) was introduced into the PSC structure as an ETL, due to its excellent electrical and optical properties, to improve electron extraction efficiency, with a doping amount of 4 at.% of vanadium. The latter has been optimized in our previous study. On the other hand, extrinsically doping TiO2 with an amount of 5 at.% of Yttrium (YTiO2) was utilized to enhance its physicochemical properties. The PSC based on VZnO/YTiO2 bilayer ETL possess the best PCE of 15.1%, compared to 9.4% in the pristine ZnO-based ETL solar cell, with the open-circuit voltage (Voc) of 923 mV, short-circuit photocurrent density (Jsc) of 22 mA cm−2, and fill factor (FF) of 74%. Obtained improvements are ascribed to the suppressed charge recombination via the incorporation of YTiO2 flower-like nanostructures at the interface VZnO/perovskite and the enhanced electron transporting in the resulting ETL bilayer structure.