Unusual temperature dependences of the photoconductivity and recombination luminescence of amorphous molecular semiconductors doped with ionic dyes

A nonexponential increase in photoconductivity with increasing temperature is discovered for poly(N-epoxypropylcarbazole) (PEPK) films doped with polymethine dyes. It is postulated that traps for nonequilibrium charge carriers form in these films during irradiation and are destroyed as the temperature is raised. Such traps are manifested by broadening of the high-temperature shoulder on the thermally stimulated luminescence (TSL) curves following the preliminary irradiation of PEPK films doped with polymethine and xanthene ionic dyes in the visible or UV range at 250-320 K and by the appearance of a new narrow TSL maximum near the preliminary irradiation temperature. These TSL features disappear after prolonged storage of the films in the dark or heating to higher temperatures. (C) 1999 American Institute of Physics. [S1063-7834(99)00502-X].