Optimisation of diketopyrrolopyrrole:fullerene solar cell performance through control of polymer molecular weight and thermal annealing - Huang, Z; Fregoso, EC; Dimitrov, S; Tuladhar, PS; Soon, YW; Bronstein, H; Meager, I; Zhang, W; McCulloch, I; Durrant, JR (JOURNAL OF MATERIALS CHEMISTRY A, 2014)