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

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 Förster 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. Förster energy transfer and carrier trapping are considered to be the main mechanisms for exciton formation on TMPVB molecules under electrical excitation.