Degradation behavior of planar heterojunction CH3NH3PbI3 perovskite solar cells

The stability and degradation process of low-temperature, solution-processed planar heterojunction perovskite solar cells (PHJ-PSCs) with a structure of ITO/PEDOT:PSS/CH3NH3PbI3/PCBM/Al were studied in both nitrogen-filled glovebox and ambient environment (humidity similar to 45%). The results suggested that PHJ-PSCs stored in glovebox without encapsulation showed good stability, and the power conversion efficiency (PCE) could be kept over 70% of original value even after 30 days. As compared, PHJ-PSCs stored in ambient environment without encapsulation showed an obvious degradation, and the PCE was about 35% of original value just after 1 h exposure in air. However, PHJ-PSCs fabricated with CH3NH3PbI3 thin films stored in ambient environment for the different times didn't show obvious degradation and have the similar performance parameters, suggesting that the degradation of PHJ-PSCs mainly resulted from the interface issues rather than the attenuation of perovskite thin film itself. Furthermore, electrochemical impedance spectroscopy (EIS) characterization indicated that the degradation of photovoltaic performance parameters was prevailingly attributed to the interface degradation. The research provides good understanding to the stability and degradation process of low-temperature, solution-processed PHJ-PSCs, which would facilitate the stability improvement of PHJ-PSCs. (C) 2017 Elsevier B.V. All rights reserved.