Photostability Study of Inverted Polymer Solar Cells Under AM 1.5G and LED Illumination via Impedance Spectroscopy

The use of polymer solar cells (PSCs) for indoor dim-light energy harvesting has attracted significant interest for low power consumption electronics such as the Internet of Things. However, the photostability study and degradation mechanism under indoor artificial light is far behind than those under full sun illumination (standard AM 1.5G), which is crucial for the successful commercialization of indoor PSCs. Herein, the operational lifetime and photodegradation mechanism of PTB7-Th:PC70BM-based inverted PSCs degraded under standard AM 1.5G and 1000 lux LED 2700K light sources were compared. A high power conversion efficiency (PCE) of up to 16.19% and a long operational lifetime (T80) of 3060 min were achieved by LED-irradiated devices, higher and more stable than that of AM 1.5G-irradiated devices with PCE of 9.98% and T80of only 260 min. Using impedance spectroscopy and three resistive-capacitive equivalent circuit model, we were able to identify the most suffered layer. Our results demonstrate that PSCs have potential practical applications as high performance and a high stable indoor power source.