Revealing ultrafast relaxation dynamics in six-thiophene thin film and single crystal

•Ultrafast relaxation dynamics of six-thiophene film/crystal after excitation to lower and upper excited states was studied.•The first direct singlet fission in six-thiophene system with subsequent triplet-triplet annihilation in film was approved.•Enhanced lifetime of photocarriers (polarons) was obtained in 1 ms for crystal compared with 130–3700 ns for film.•Efficient polarons formation was approved (four times larger) upon excitation to upper excited singlet state (4.96 eV).