Stability and reliability of P3HT:PC61BM inverted organic solar cells

Improving the stability and reliability of organic photovoltaic (OPV) devices is an area of intense research as it is the major barrier in the commercialization of these devices. We study the stability of inverted structured OPV devices in the present work. A large number of these were fabricated and their shelf life times were recorded. P3HT devices show an average T80 (time in which cell efficiency falls to 80% of its initial value) of 34 days. Some of the devices were tested in actual working conditions outdoors in sunlight. A very low T80 value of 12 h was observed during the outdoor testing. Thermal degradation study was performed on the devices at 65 °C in dark and an average T80 of 200 h was obtained. Signatures of trap formation were observed by analysing and comparing the dark current-voltage characteristics of the pristine and degraded devices. The solar cells degrade due to trap formation in the active layer and formation of charge extraction barriers at the contacts.