Vitamin C for Photo-Stable Non-fullerene-acceptor-Based Organic Solar Cells

Abstract

The recent advent of the new class of organic molecules,the so-callednon-fullerene acceptors, has resulted in skyrocketing power conversionefficiencies of organic solar cells. However, rapid degradation occursunder illumination, particularly when photocatalytic metal oxide electrontransport layers are used in these devices. We introduced vitaminC (ascorbic acid) into the organic solar cells as a photostabilizerand systematically studied its photostabilizing effect on invertedPBDB-T:IT-4F devices. The presence of vitamin C as an antioxidantlayer between the ZnO electron transport layer and the photoactivelayer strongly suppressed the photocatalytic effect of ZnO that inducesNFA photodegradation. Upon 96 h of exposure to AM 1.5G 1 Sun irradiation,the reference devices lost 64% of their initial efficiency, whilethose containing vitamin C lost only 38%. The UV-visible absorption,impedance spectroscopy, and light-dependent voltage and current measurementsreveal that vitamin C reduces the photobleaching of NFA moleculesand suppresses the charge recombination. This simple approach usinga low-cost, naturally occurring antioxidant, provides an efficientstrategy for improving photostability of organic semiconductor-baseddevices.