Effect of dopant concentration on charge transport in crosslinkable polymers



Crosslinkable polymer hole-only structures have been characterized by current–voltage, and admittance spectroscopy. Our hole transport layer (HTL) consists of a triphenylene-diamine derivative (QUPD) crosslinked after deposition with a photoinitiator. The crosslinking leads inadvertently to doping of the HTL depending on the initiator concentration. We study the influence of doping on charge transport in the HTL. We show that the increase of low-frequency capacitance with increasing voltage and dopant concentration, as well as the low-voltage region in the (JV) characteristics are injection limited. At higher voltages, the transport is space-charge limited (SCL) with a field-dependent mobility. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)