Influence of an electrode self-protective architecture on the stability of inverted polymer solar cells based on P3HT:PCBM with an active area of 2 cm2

In this paper, we study the performance and stability of solution-processed inverted organic solar cells based on photoactive blends composed by the conjugated regioregular poly-(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), using an active area of 2 cm(2). These inverted organic solar cells are fabricated with a novel top electrode design in which the silver electrode is deposited over the whole substrate to completely cover the photoactive layer, allowing an effective protection of the entire device. Consequently, initial power conversion efficiencies of 3.2% are maintained at 90% after 15 h under standard illumination conditions in ambient atmosphere. Light beam induced photo-voltage (LBIV) maps have been recorded to monitor the uniformity of the photo-response on the whole active area, and revealed the effectiveness of our design to prevent lateral moisture and oxygen diffusion. The dependency of short-circuit current density on incident light intensity, combined with LBIV data, indicates that the degradation of performance arises from dark spots which reduce the active layer area, rather than from an intrinsic aging of the active layer. Taking into account these observations, we rationalize the time evolution of device efficiency upon degradation for both non-encapsulated and encapsulated devices. (C) 2015 Elsevier B.V. All rights reserved.