In-situ passivation of TiO₂ mesoporous scaffold with nano-sized heteropolyacid for boosting the efficiency of the perovskite solar cells

TiO₂ is a widely used electron transport layer for high efficiency perovskite solar cells. However, many intrinsic shortcomings seriously deteriorate the devices performance. Herein, we demonstrate a facile and effective approach to improve the photovoltaic performance by passivating the TiO₂ mesoporous layer with a nanoscale dispersed 12-tungstophosphoric heteropolyacid (H₃PW₁₂O₄₀·nH₂O). Due to the strong interaction between H₃PW₁₂O₄₀·nH₂O and TiO₂, the passivated TiO₂ mesoporous electron transport layer (hereafter denoted as PW₁₂/TiO₂) with an optimal weight ratio shows a more uniform coverage on the underlying substrate in comparison with the bare TiO₂. Furthermore, the resulted PW₁₂/TiO₂ also shows an obviously improved conductivity and significantly increased photoluminescence quenching for the perovskite emission. Thereby, this strategy leads to an apparently improved photovoltaic performance of perovskite solar cells with power conversion efficiency enhancement from 15.05% to 18.20%. In conclusion, our present study provides an effective approach for further improving the performance of perovskite solar cells by passivating the mesoporous electron transport layer with the well-known heteropolyacids.