Two sets of perylenediimide-fullerene dyads PDI-C60 connected through 1,2,3-triazole units have been synthesized and characterized. The cyclic dyad PDICl4-C60 has four chlorine atoms in the 1,6,7,12-PDI positions, whereas the cyclic dyad PDIPip2-C60 has two piperidine units in the 1,7-PDI positions. On the other hand, PDICl4-C60 and PDIPip2-C60 dyads were synthesized as linear counterparts with the same substitution pattern. Also, a C60-PDICl4-C60 triad has been prepared. A small interaction between C60 and PDI moieties in the ground state was detected by UV/vis and electrochemical measurements in both PDI-C60 cyclic systems. The occurrence of photoinduced energy-transfer processes between PDI and C60 units was confirmed by time-resolved emission and transient absorption techniques. Femtosecond laser flash photolysis showed energy transfer from 1PDI* to C60 followed by intersystem crossing from 1C60* to 3C60* in the case of the PDICl4-C60 systems. The energy transfer rate for PDICl4-C60 in the cyclic dyad and the triad is one order of magnitude faster than that in PDICl4-C60 in the linear dyad. The fast energy transfer rate together with the enhanced molar absorption coefficient by perylenediimide functionalization will be highly beneficial for applications as acceptors in polymer solar cells. On the other hand, no electron transfer from the donor PDIpip2 units to the acceptor C60 moiety was detected in the case of PDIPip2-C60 dyads.
- Click chemistry
- Photoinduced energy transfer