Charge photogeneration effect on the exciplex emission from thin organic films

The photoexcited singlet and triplet exciplex emission of thin photocondcuctive films containing an amine derivative N,N-'-diphenyl-N,N-'-bis(3-methylphenyl)-1,1(')-biphenyl-4,4(')diamine (TPD) electron donor and the bathophenathroline (BPT) electron acceptor drops largely with electric fields, falling down to about 20% of its zero-field value at high fields. This strong electric-field-induced exciplex emission quenching is interpreted in terms of the charge-imposed decay of singlet molecular excitons of TPD acting as precursors of the exciplexes and charge photogenerated on the TPD:BPT contacting sites. The favorable interrelation between the ionization potential of the donor and electron affinity of the acceptor leads there to an efficient field-enhanced exciton dissociation. The electrons trapped on acceptor molecules act in turn as charged exciton quenching centers. (c) 2006 American Institute of Physics.