Abstract

Optical absorption in organic semiconductors creates tightly bound electron-hole pairs, known as excitons. Generation of charge carriers occurs when the excitons break into positive and negative polarons;¹ this process is relevant to the performance of photovoltaic devices. Exciton dissociation can be affected by an external electric field and limits the electroluminescence efficiency in organic light-emitting diodes (LEDs), being a nonradiative decay channel. Transient measurements of field-induced photoluminescence quenching in poly-(para-phenylene) films have shown that the primary step of charge generation occurs in the picosecond time domain.² Such experiments are indirect probes and cannot monitor the state produced by the exciton dissociation, the nature of which is currently under debate.^2-3

© 1998 Optical Society of America