Highly Efficient, Solution Processed Electrofluorescent Small Molecule White Organic Light-Emitting Diodes with a Hybrid Electron Injection Layer

Highly efficient, solution-processed, and all fluorescent white organic light-emitting diodes (WOLEDs) based on fluorescent small molecules have been achieved by incorporating a low-conductivity hole injection layer and an inorganic-organic hybrid electron injection layer. The light-emission layer is created by doping a fluorescent pi-conjugated blue dendrimer host (the zeroth generation dendrimer, GO) with a yellow-emitting fluorescent dopant oligo(paraphenylenevinylene) derivative CN-DPASDB with a doping ratio of 100:0.15 (GO:CN-DPASDB) by weight. To suppress excessive holes, the high-conductivity hole injection layer (PEDOT:PSS AI 4083) is replaced by the low-conductivity PEDOT:PSS CH 8000. To facilitate the electron injection, a hybrid electron injection layer is introduced by doping a methanol/water-soluble conjugated polymer poly[(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFNR2) with solution-processed cesium fluoride (CsF). The device achieves a maximum luminous efficiency of 17.0 cd A(-1) and a peak power efficiency of 15.6 lm W-1 at (0.32, 0.37) with a color rendering index of 64.