Effect of addition of a diblock copolymer on blend morphology and performance of poly(3-hexylthiophene):perylene diimide solar cells

Effect of addition of a diblock copolymer on blend morphology and performance of poly(3-hexylthiophene):perylene diimide solar cells was studied. A combination of regioregular P3HT for the thiophene component of the diblock copolymer and a comb polymer was considered an ideal target for the compatibilizer studies. Reversible addition-fragmentation chain transfer (RAFT) was chosen for this purpose because of the relatively mild reaction conditions and exceptional control over molecular weight distribution. AFM studies showed the formation of micrometer sized perylene crystals on the surface of thin films cast from CHCl ₃ solutions of P3HT and perylene tetracarboxydiimide (PDI). After optimization of various device parameters including annealing conditions, composition of the active layer, and the choice of solvent for spin-casting, the devices with a VOC of 0.56 V, J _SC of 1.85 mA cm ^-2, and a fill factor of 0.51 was obtained when perylene was used. The device with compatibilizer shows a maximum EQE of 19%, compared to less than 16% for the control.