上海科技大学知识管理系统

We study the ultrafast photoexcitation dynamics in PBDTTT-C-T (P51, poly(4,8-bis(5-(2-ethylhexyl)-thiophene-2-yl)-benzo[1,2-b:4,5-b ']dithiophene-alt-alkylcarbonyl-thieno[3,4-b]thiophene)) film (similar to 100 nm thickness) and PBDTTT-C-T:PC71BM (P51:PC71BM, phenyl-C-71-butyric-acid-methyl ester) nanostructured blend (similar to 100 nm thickness) with/without DIO(1,8-diiodooctane) additives with sub-10 fs transient absorption (TA). It is revealed that hot-exciton dissociation and vibrational relaxation could occur in P51 with a lifetime of similar to 160 fs and was hardly affected by DIO. However, the introduction of DIO in P51 brings a longer lifetime of polaron pairs, which could make a contribution to photocarrier generation. In P51:PC71BM nanostructured blends, DIO could promote the Charge Transfer (CT) excitons and free charges generation with a similar to 5% increasement in similar to 100 fs. Moreover, the dissociation of CT excitons is faster with DIO, showing a similar to 5% growth within 1 ps. The promotion of CT excitons and free charge generation by DIO additive is closely related with active layer nanomorphology, accounting for J(sc) enhancement. These results reveal the effect of DIO on carrier generation and separation, providing an effective route to improve the efficiency of nanoscale polymer solar cells.