Role of photoactive layer morphology in high fill factor all-polymer bulk heterojunction solar cells

We report on the realization of all-polymer solar cells based on blends of poly(3-hexylthiophene-2,5-diyl) (P3HT) as a donor and poly{[N,N′-bis(2- octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5, 5′-(2,2′-bithiophene)} (P(NDI2OD-T2)) as an acceptor. High fill factors are demonstrated for the first time in this class of devices suggesting high dissociation efficiency for the bounded electron-hole pairs and balanced electron and hole mobility along the thin films. The use of the high-mobility n-type P(NDI2OD-T2) polymer enables us to overcome one of the problems limiting the efficiency of all-polymer solar cells, resulting in fill factors comparable with those reported for fullerene-based devices.