Geminate pair dissociation in random organic systems

The temperature dependences of (i) intrinsic photogeneration, (ii) photoinjection of holes from an indium tin oxide (ITO) electrode via excited state dissociation at the interface and (iii) dark injection from an ITO anode have been studied for a variety of random organic systems. They approach activated behavior in the high-temperature limit while at lower temperature, typically T < 200 K, the yield becomes temperature-independent and, concomitantly, exceeds the yield expected for energetically ordered systems. The effect is in accord with recent simulation work on geminate pair dissociation in energetically disordered hopping systems.