Femtosecond transient photophysics of polyfluorene copolymers tuned by carbazole side group

► New polyfluorene-thiophene-benzothiadiazole three group polymer system studied. ► In solution, carbazole on side chain show steric hinderance and reduce interband energy transfer. ► In film, ultrafast exciton-exciton annihilation is stronger without carbazole side-chain. ► With presence of carbazole on side chain, polaron-pair decay was resolved much stronger.