Yadong Jin

Single-layer organic light-emitting diode with 2.0% external quantum efficiency prepared by spin-coating

We present a highly efficient organic light-emitting diode with a single-layer structure and air-stable Al cathode. The device consists of a spin-coated thin film of polystyrene in which rubrene and Alq3 molecules are dispersed. By optimizing the concentration of Alq3 and rubrene, a maximum external quantum efficiency of 2.0% photons/electron and a current efficiency of 8.5 cd/A at 22 V could be achieved in the device. The high electroluminescence efficiency is attributed to a combination of energy transfer from Alq3 to rubrene, and direct carrier trapping and recombination on rubrene, followed by an efficient fluorescent emission from rubrene.

Efficient blue polymer light-emitting diodes from a novel biphenyl derivative

Abstract A novel blue-emitting soluble biphenyl derivative 4,4-bis[2-(3,4,5-trimethoxyphenyl)vinyl]biphenyl (TMPVB) was synthesized. It was dispersed into poly[2-(6′-cyano-6′-methylheptyloxy)-1,4-phenylene] (CNPPP), to form a blend film as the emissive layer in organic light-emitting diodes (OLEDs). Efficient Forster energy transfer from CNPPP to TMPVB molecules is proved in this film. We find that the emission is dominantly from the TMPVB molecules during the device operation. The best performing device has a peak external quantum efficiency of 1.2%, which is comparable to the best results obtained for devices based on blue-emitting polymers. Forster energy transfer and carrier trapping are considered to be the main mechanisms for exciton formation on TMPVB molecules under electrical excitation.

Blue light emitting diodes(LED) based on alkoxy substituted biphenyl trimer as guest

A novel blue emission compound containing biphenyl and stilbene moieties is developed. An investigation of a LED based on this compound blended as guest in Poly (N-vinylcarbazole)PVK matrix is presented. Insertion of a thin LiF layer between the aluminum and active layer results in enhanced quantum efficiency (QE) and brightness. The QE reaches 0.4%, using Aluminum(Al) only as cathode, when 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) is introduced to the blend matrix.