Photoinduced absorption spectroscopy of oligotmophene/C/sub 60/ mixtures in films and solution

Summary form only given. The recent discovery of photoinduced electron transfer from /spl pi/-conjugated polymers onto C/sub 60/is extended exploring a series of well-defined /spl alpha/-oligothiophenes. Using photoinduced absorption spectroscopy we demonstrate the effective quenching of the luminescence and intersystem crossing of the singlet photoexcited state in solid oligothiophene films via a fast electron-transfer reaction. In solution, on the other hand, the primary reaction of C/sub 60/with the photoexcited oligothiophene is not an electron transfer, but an efficient transfer of energy from the triplet photoexcited oligomer to C/sub 60/ instead. Luminescence and intersystem crossing rates of oligothiophenes are not affected by C/sub 60/ in solution. The observed electron and energy transfer are employed to study polaronic and bipolaronic nonlinear excitations of oligothiophenes and the effect of the increasing conjugation length is discussed.