Enhanced efficiency and stability of perovskite solar cells with ultra-thin Al2O3 contact interlayer via low temperature atomic layer deposition

Abstract

Long-term stability of organic-inorganic metal halide perovskite solar cells (PSCs) is a prerequisite for their successful commercialization. Electrode failure is one of the most critical reasons for the degradation of perovskite solar cells during aging test. The electrode failure is dominantly due to corrosion of metal contacts by the iodine ion migrated from the perovskite active layer. To conquer the instability of PSCs, we inserted a compact ultra-thin Al₂O₃interlayer between electron transfer layer and metal contact by atomic layer deposition (ALD) processed at 65℃. Experimental results show that 8 deposition cycle ALD Al₂O₃ thin film (~2 nm) improve the efficiency as well as the stability of the PSCs. It is found that the Al₂O₃ layer plays an important role of blocking iodide ion migration, preventing moisture and oxygen penetration and improving the efficiency of electron extraction. Statistically, the perovskite solar cells achieve a power conversion efficiency (PCE) of 19.50% (V_ocof 1.061 V, and J_scof 23.03 mA/cm²), and remain 80% of its initial performance after 1200 hours of storage in ambient air condition, also remained 97.4％ of its initial performance when heated at 85℃ for 48 hours. Compared to the devices without ALD Al₂O₃ interlayer, the PCE is improved 12%, and the stability is extended for 400 hrs. This work highlights the importance of introducing ultra-thin compact ion blocking layer to the high performance perovskite solar cell devices.