The thermally stable hole transport layer (HTL) materials, 1,4-bis[(N,N'-di(2-naphthyl)-N,N'-diphenyl) aminophenyl]triphenylene (NPAPT) and 1,4-bis[(N,N'-di(2-naphthyl)-N,N'-diphenyl) aminophenyl]-2,3-diphenyl triphenylene (NPAPPT), were synthesized and the device performances of the organic light-emitting diodes (OLEDs) with NPAPT and NPAPPT as a hole transport layer were investigated. The glass transition temperatures of NPAPT and NPAPPT could be enhanced to 153 degrees C and 157 degrees C by the introduction of a rigid triphenylene backbone in the main chain. The use of NPAPT and NPAPFT as a HTL for OLEDs lowered the driving voltage and enhanced the light-emitting efficiency. The power efficiencies of triphenylene-based devices with tris(8-hydroxyquinoline)aluminum as an emitting material could be improved by 20% compared with that of N,N'-di(naphthalene-1-yl)-N,N'-diphenyl benzidine based devices. (C) 2011 Elsevier B.V. All rights reserved.