Investigation of multi-donor bulk-heterojunction photovoltaic cells based on P3HT:PCBM system

(2,7-bis[5′-(9,9-dioctylfluorene-2-yl)-2,2′-dithienyl-5-yl]-9,9-dioctylfluorene) (F3Th4) was used as a secondary electron donor material in the poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) bulk-heterojunction photovoltaic cell. It is shown that the combination of F3Th4 with P3HT allows strong light absorption. The mechanism of charge transfer in the multi-donor PV cell was investigated; it shows that efficient energy transfer takes place from F3Th4 to P3HT. However, the short-circuit current (JSC) of the multi-donor bulk-heterojunction photovoltaic (PV) cell still decreased. The possible reason for the smaller photocurrent is worsening of transport property after addition of F3Th4.