The Effect of Al2O3 on the Performance of Perovskite Solar Cells.

Improving the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs) remain the two most important goals of perovskite research. Herein, the effects of Al2O3 interlayer on the performance of formamidinium‐cesiums and "triple cation" PSCs by depositing a thin Al2O3 layer via atomic layer deposition on different interfaces are analyzed. It is found that it can efficiently serve as a passivation layer of perovskite absorber, as a seed layer for the compact growth of the subsequent SnO2 layer, or as a capping layer to the whole cell in the superstrate configuration to prevent moisture ingress. The optimized devices utilizing Al2O3 have on average more than 1% absolute higher PCE, with reduced penetration of moisture inside the device. Especially, the capping layer has shown the greatest benefit, extending the stability of the devices by more than two times and allowing long‐term operation without encapsulation. In the best case, a T80 time of almost 900 h under day/night‐cycling illumination is obtained. The observed trends are based on data from a large number of devices (more than 300 devices were tested in the maximum power point), which give statistical relevance to the promising results. [ABSTRACT FROM AUTHOR]