Low temperature reactively sputtered crystalline TiO2 thin film as effective blocking layer for perovskite solar cells

A uniform and compact hole blocking layer is necessary for a high performance perovskite solar cells, as it not only serves as an electron collector but also represses the electron recombination by blocking direct contact between the transparent conducting oxide and the perovskite layer. So far, highly performing perovskite solar cells have been achieved using a blocking layer that requires sintering at high temperatures (> 450 °C). In this study, reactive magnetron sputtering was used to synthesise crystalline anatase TiO2 thin film blocking layer at a moderate temperature (150 °C). The influence of block layer thickness on the photovoltaic performance is scrutinised. A high performance of 8.7% power conversion efficiency was obtained for perovskite solar cells with a 76 nm thick TiO2 blocking layer. This low temperature synthesis method will extend the choice of substrate to cheap and flexible polymer substrates. The surface plasma treatment prior to the blocking layer deposition was also found to affect the performance of the solar cells.