Exploring low-temperature processed a-WOx/SnO2 hybrid electron transporting layer for perovskite solar cells with efficiency >20.5%

Interfacial engineering strategy between the perovskite absorber and the charge transport layer play a vital role in highly efficient perovskite solar cells. Here, we propose an amorphous tungsten oxides/tin dioxide hybrid electron transport layer to effectively block holes through the pinholes and cracks of tin dioxide to indium tin oxide, resulting in promoting charge extraction and hindering electron-hole recombination process at the hetero-interface. Moreover, owing to the higher mobility of amorphous tungsten oxides and formation of cascade energy level sequence between amorphous tungsten oxides and tin dioxide, better electron transport is obtained compared with the traditional electron transport layer. The PSCs based on amorphous tungsten oxides/tin dioxide hybrid electron transport layer shows a better power conversion efficiency of 20.52% than the single tin dioxide electron transport layer. This study guides design strategies of the electron transport layer to enhance the efficiency of the perovskite solar cells by interfacial engineering. Moreover, the entire devices preparation process are finished at a temperature below 150 °C, promising great potential for the practical use in monolithic tandem devices and providing an avenue for the progress of flexible device.