Excited state dynamics in cross-linked covalent hybrids of graphene and diketopyrrolopyrrole oligomers revealed via ultrafast pump-probe and 2D spectroscopy

Cross-linked covalent hybrids of graphene and diketopyrrolopyrrole (TDPP) oligomers were studied via ultrafast pump-probe and 2D electronic spectroscopy with sub 30 femtosecond time resolution. Comparisons between polymerizing (c-EXG-TDPP) and non-polymerizing (EXG-TDPP) hybrids show that charge/energy transfer occurs faster than 50 ps in EXG-TDPP, while the c-EXG-TDPP system quenches within 18 ps. The transient response of c-EXG-TDPP is completely quenched (>99%); full quenching occurs in EXG-TDPP after 1.39 ns. Photocurrent studies of c-EXG-TDPP films show IPCE > 2%, indicating ultrafast charge transfer between the TDPP moeity and graphene.