Interfacial layer for efficiency improvement of solution-processed small molecular solar cells

•The PCE of solution-processed small molecular solar cells (SMSCs) arrives to 2.68%.•The roughness of MoO3 increases the interfacial area between anode and active layer.•JscVoc, and FF of cells with MoO3 as anode interfacial layer are improved about 54.7%, 26.9%, and 23.5%.

A series of solution-processed small molecular solar cells (SMSCs) were fabricated with 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] (DIB-SQ) and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) as the active layer. The cells with MoO3 as anode interfacial layer and LiF as cathode interfacial layer have the maximum power conversion efficiency (PCE) 2.68%, with short circuit density (Jsc) of 8.2 mA/cm2, open circuit voltage (Voc) of 0.9 V and fill factor (FF) of 36.3% under 100 mW/cm2 illumination intensity. The key parameters, including JscVoc, and FF of cells with MoO3 as anode interfacial layer and LiF as cathode interfacial layer, are improved about 54.7%, 26.9%, and 23.5% compared with these of cells using PEDOT:PSS as anode interfacial layer and LiF as cathode interfacial layer. The underlying reasons are mainly attributed to the effect of MoO3 layer on charge carrier collection and morphology of active layer. The effect of illumination intensity on the performance of cells was also discussed in detailed.