Researchers from Sungkyunkwan University recently reported the development of highly stable perovskite solar cells under extreme environments by improving passivation techniques.
The architecture of the solar cells has inverted planar devices (so-called p-i-n devices; light illumination through hole transport layers) with FTO/NiO/Perovskite/PCBM/AZO/Ag. AZO has been deposited via atmoic layer deposition method, which produces pinhole-free, uniform, and dense films. The AZO-deposited perovskite solar cells exhibited similar performances to the control solar cells due to negligible charge transporting retardation by the 3 orders of magnitude higher conductivity of AZO compared to that of PCBM. The ALD-grown AZO (ALD-AZO) layers also acted as dense, uniform, and impermeable passivation layers that prevented ingress of water into the perovskite films, egress of the volatile components of perovskite when heated, and interfacial degradation between the perovskite-PCBM heterojunction and the Ag electrode caused by unfavorable chemical reactions.
The team found that the stability of perovskite solar cells with an AZO layer is superior to the control devices. While the control solar cells degraded rapidly under light illumination at room temperature in spite of an additional passivation layer, AZO-perovskite solar cells maintained 99.5% of their initial efficiency for 500 hours. The unique role of AZO, distinguished from additional passivating layers, is to prevent moisture penetration as well as interdiffusion at the perovskite/Ag interface when illuminated.
These perovskite solar cells showed their stability in a more severe environment, exhibiting a power conversion efficiency of 18.45% and retaining 86.7% of their initial efficiency for 500 hours under continuous 1-sun illumination at 85°C in ambient air with electrical biases (at the maximum power point).