A series of oligofluorenes ranging between one and three repeating units were prepared as structurally well-defined representative models of polyfluorenes. The photophysics of the oligofluorene models were investigated both by laser flash photolysis and steady-state fluorescence. The effects of the ketone and ketylimine functional groups in the 9-position on the photophysical properties, notably the triplet quantum yield (Phi(TT)) by intersystem crossing and the absolute fluorescence quantum yields (Phi(fl)) were investigated. The singlet depletion method was used to determine both the Phi(TT) and molar absorption coefficients of the observed triplets (epsilon(TT)) Meanwhile, the absolute (Phi(fl)) were determined using an integrating sphere. It was found that both the ketone and ketylimine substituents and the degree of oligomerization contributed to quenching the oligofluorene fluorescence. For example, the Phi(fl) was quenched 5-fold with the ketylimine and ketone substituents for the bifluorenyl derivatives compared to their corresponding 9,9-dihexyl bifluorenyl counterparts. Meanwhile, the Phi(fl) quenching increased 14 times with the trifluorenyl ketone and ketylimine derivatives. Measured Phi(TT) values ranged between 22 and 43% for the difluorenyl derivatives with epsilon(TT) the order of 13 000 cm(-1) M-1. The Phi(TT) decreased to <10% concomitant with doubling of the epsilon(TT) when the degree of oligomerization was increased to 3. A new fluorescence emission at 545 nm formed at low temperatures for the ketone and ketylimine oligofluorene derivatives. The emission intensity was dependent on the temperature, and it disappeared at room temperature.