Dissociation of excitons in organic dye layers of perylene derivatives

The dissociation processes of excited states in vapor-deposited thin films of N,N'-dimethylperylene-3,4,9,10-dicarboximide (Me-PTCDI) and 3,4,9,10-per ylenetetracarboxylic dianhydride (PTCDA) are investigated in detail by mean s of electric field induced fluorescence quenching and photoresponse. The d ecay mechanisms of the two materials are quite different: Time resolved fie ld induced fluorescence quenching on Me-PTCDI shows rate type quenching. Tw o spectral ranges with different field dependencies and decay times were ob served. An efficient dissociation requires external fields of up to 2 x 10( 6) V/cm. In PTCDA films, the quenching is of both rate and amplitude type. For this material, two spectral ranges with different field dependencies ar e recorded. A field induced luminescence enhancement is measured in the ran ge between 520 and 600 nm. The combination of the fluorescence quenching me asurement with the relative photoresponse and absolute luminescence quantum yield of Me-PTCDI allows to estimate the decay rate constants of the visib le states of Me-PTCDI. (C) 2000 Elsevier Science S.A. All rights reserved.