Polymer light-emitting diodes with doped hole-transport layers

Abstract

We demonstrate a solution processed bi-layer PLED based on poly(p-phenylene vinylene) derivatives using orthogonal solvents. To lower the voltage drop the hole transport layer (HTL) based on poly[2,5-bis(2'-ethylhexyloxy)-co-2,5-bis(butoxy)-1,4-phenylenevinylene] (BEH/BB-PPV (1: 3)) is doped with tetracyano-tetrafluoro-quinodimethane (F4TCNQ). The conductivity of BEH/BB-PPV (1: 3) was observed to increase by two orders of magnitude upon doping with F4TCNQ. The doped HTL was observed to lower the operating voltage of a double layer PLED, but suffers from additional quenching by the dopant at higher voltages due to the lack of an electron blocking functionality. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim