Relaxation of the excited states and analysis of the photocurrent spectrum of C60 polycrystalline films

Excitation relaxation processes in C60 thin film are investigated by means of steady state photoconductivity and photoluminescence. The photocarrier generation efficiency Φ(λ) has been calculated in terms of the bimolecular recombination limited model for the bulk-generated charge carriers. The photocarrier generation efficiency is almost wavelength independent in the rang 300⪯λ⪯600nm whereas it is strongly wavelength dependent for λ⪰600nm. The electric field induced fluorescence quenching has been observed and its efficiency is dependent on the excitation wavelength. A tentative interpretation of the excitation relaxation process is proposed invoking charge transfert states.