Non-doped white organic light-emitting diodes using an ultrathin yellow-emitting layer of rubrene (5,6,11,12-tetraphenylnaphtacene) inserted on either side of the interface between a hole-transporting NPB (4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl) layer and a blue-emitting DPVBi (4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl) layer are described. Both the thickness and the position of the rubrene layer allow fine chromaticity tuning from deep-blue to pure-yellow via bright-white with CIE coordinates (x= 0.33, y= 0.32), a external quantum efficiency of 1.9%, and a color rendering index of 70. Such a structure also provides an accurate sensing tool to measure the exciton diffusion length in both DPVBi and NPB (8.7 and 4.9 nm respectively).
@article{arxiv.physics/0609238,
title = {White Organic Light-Emitting Diodes with fine chromaticity tuning via ultrathin layer position shifting},
author = {Hakim Choukri and Alexis Fischer and Sebastien Forget and Sebastien Chenais and Marie-Claude Castex and Dominique Ades and Alain Siove and Bernard Geffroy},
journal= {arXiv preprint arXiv:physics/0609238},
year = {2009}
}