1,3-diphenyl-5-(9-phenanthryl)-4,5-dihydro-1H-pyrazole (DPPhP):: structure, properties, and application in organic light-emitting diodes

A novel hole-transport material, 1,3-diphenyl-5-(9-phenanthryl)-4,5-dihydro-1H-pyrazole (DPPhP), was synthesized and fully characterized. The crystal structure of DPPhP was determined by X-ray diffraction analyses. DSC and AFM analysis demonstrate that DPPhP has a high T-g of 96 degreesC and good film forming ability. The hole-transport performance of DPPhP was examined by fabricating a multilayer device with structure of ITO/DPPhP (60 nm)/AlQ (60 nm)/LiF (0.8 nm)/Al, using DPPhP as the hole-transport layer along with an emitting-material, tris-(8-hydroxyquinolino) aluminium (AlQ). Both the brightness and efficiency of the device are about 30% higher than those of the device using N,N'-di-1-naphthenyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (alpha-NPD) as the hole-transport layer.