Reduced initial degradation of bulk heterojunction organic solar cells by incorporation of stacked fullerene and lithium fluoride interlayers

Reduced initial degradation of bulk heterojunction organic solar cells (OSCs) was achieved by inclusion of stacked fullerene (C60) and lithium fluoride interlayers. By inserting a 3 nm C60 layer and a 0.5 nm LiF layer between the photoactive layer and Al cathode in an OSC, the device lifetime calculated after an initial 8 h continuous illumination period was dramatically improved, with a decrease of only 5% in the power conversion efficiency. The 3 nm C60 layer forms a unique surface pattern of microscopic domes, and the combination of this layer with a 0.5 nm LiF layer formed an Ohmic-like contact between the photoactive layer and the Al cathode, resulting in a significant reduction in the degradation of the OSC.