Charge injection and transport in a green emitting polyfluorene

摘要

Experimental studies of charge injection and transport of holes and electrons in LUMATION™ Green 1300 Series light-Emitting Polymer (LEP) by dark injection space-charge-limited technique are performed. It is found that hole mobility is lower than electron mobility and the former exhibits steeper electric field dependence thus reducing the disbalance between charge mobilities at higher device operating voltages. Electron current is affected by trapping, mainly due to deep traps prevailing at low electric fields and with an estimated concentration of 10~(16) cm~(-3). Hole current is affected both by trapping and injection limitation, with the trapping being approximately independent of electric field and injection efficiency increasing with increasing electric field. Electron trapping is found to be significantly reduced in dual carrier devices, which is believed to be the effect of faster exciton formation and recombination rates, compared to electron trapping processes.