Blue light emitting diode with 1,1,4,4-tetraphenyl-1,3-butadiene (TPB)

Blue electroluminescence (EL) devices with the structure ITO/poly(N-vinylcarbazole) (PVK):1,1,4,4-tetraphenyl-1,3-butadiene (TPB):triphenylamine (TPA)/Al have been studied. PVK doped with TPB was used for hole transport layer (HTL) and emitting layer (EML). The triphenylamine contributed to the small band width of blue emission. TPB is known as a blue-emitting material. In addition, the wavelength of blue emission observed from PVK:TPB (3 mol%) is almost 450 nm, which is the recommended blue emission wavelength. In this work, a TPA doping effect on full-width at half maximum (FWHM) observed from TPB:TPA-doped PVK devices is demonstrated. To investigate the role of TPB at the ITO/PVK:TPB:TPA layer interface, the morphology of the PVK:TPB:TPA layer on ITO was studied with atomic force microscopy (AFM).