Comparison of conventional and inverted structures in fullerene-free organic solar cells

A n-type small molecule DC-IDT2F, with 4,4,9,9-tetrakis(4-hexylphenyl)-indaceno[1,2-b:5,6-b']dithiophene as a central building block, furan as pi-bridges, and 1,1-dicyanomethylene-3-inclanone as end acceptor groups, was synthesized and used as an electron acceptor in solution-processed organic solar cells (OSCs). DC-IDT2F exhibited good thermal stability, broad and strong absorption in 500-850 nm, a narrow bandgap of 1.54 eV, LUMO of -3.88 eV, HOMO of -5.44 eV and an electron mobility of 6.5 x 10(-4) cm(2)/(Vs). DC-IDT2F-based OSCs with conventional and inverted structures exhibited power conversion efficiencies of 2.26 and 3.08%, respectively. The effect of vertical phase separation and morphology of the active layer on the device performance in the two structures was studied. (C) 2015 Science Press and Dalian Institute of Chemical Physics. All rights reserved.