Degradation in organic solar cells under illumination and electrical stresses in air

Abstract

The degradation phenomenon in small molecular organic solar cells with an indium tin oxide (anode)/copper phthalocyanine (donor)/fullerene (acceptor)/bathocuproine (buffer)/Ag (cathode) structure is experimentally investigated. The effect of three kinds of stress, that is, air exposure, repetitive illumination, and repetitive electrical stress, on device performance is examined. Both air exposure and repetitive illumination deteriorate the device performance appreciably. The decrease in power conversion efficiency is dominated by the decrease in the fill factor. Repetitive electrical stress does not cause substantial device degradation. The degree of degradation under a combination of stresses from repetitive illumination and air exposure is lower than that under illumination stress alone. Furthermore, there is a possibility that this combination of stresses induces some passivation against further air exposure stress.