GEMINATE RECOMBINATION OF LONG-LIVED ELECTRON-HOLE PAIRS IN DOPED CARBAZOLE-CONTAINING AMORPHOUS MOLECULAR SEMICONDUCTORS

This paper reports an investigation into the features of geminate reco mbination of long-lived electron-hole pairs in films of poly(N-epoxypr opylcarbazole) (PEPC) containing intramolecular charge transfer compou nds as centers of photogeneration of charge carriers carried out by me asuring the attenuation kinetics of isothermal recombination luminesce nce over a wide range of temperatures (4.2-300 K) for times t> 1 s, al ong with the kinetics of photoinduced EPR signals. A study is made of how the presence of a potential barrier to the reverse transition of c arriers to the recombination center and the initial triplet state of t he charged pairs affects the geminate recombination. It is established that the kinetics of isothermal recombintation luminescence attenuati on follow the law I(t)proportional to t(-m) for the times under study, where m takes values from 0.65 to 1.05. The first observations of a n onmonotonic change in m with temperature are reported (m passes throug h a minimum at a certain temperature), and a mechanism is proposed for recombination of charged pairs in PEPC containing intramolecular char ge-transfer compounds as an explanation for this phenomenon. (C) 1997 American Institute of Physics.