Room-Temperature Atomic-Layer-Deposited Al2O3 Improves the Efficiency of Perovskite Solar Cells over Time

Electrical characterisation of perovskite solar cells consisting of room-temperature atomic-layer-deposited aluminium oxide (RT-ALD-Al2O3) film on top of a methyl ammonium lead triiodide (CH3NH3PbI3) absorber showed excellent stability of the power conversion efficiency (PCE) over a long time. Under the same environmental conditions (for 355d), the average PCE of solar cells without the ALD layer decreased from 13.6 to 9.6%, whereas that of solar cells containing 9 ALD cycles of depositing RT-ALD-Al2O3 on top of CH3NH3PbI3 increased from 9.4 to 10.8%. Spectromicroscopic investigations of the ALD/perovskite interface revealed that the maximum PCE with the ALD layer is obtained when the so-called perovskite cleaning process induced by ALD precursors is complete. The PCE enhancement over time is probably related to a self-healing process induced by the RT-ALD-Al2O3 film. This work may provide a new direction for further improving the long-term stability and performance of perovskite solar cells.