Red-Emission Oligofluorene Electrophosphorescent Diodes Based on Bis[2-(9,9-dihexyl-9H-fluoren-2-yl)quinolineC3,N]acetylacetonatoiridium(III) and Solvent Treatment for Interface Modification

Efficient solution-processed organic light emitting diodes based on oligofluorene doped with bis[2-(9,9-dihexyl-9H-fluoren-2-yl)quinoline-C3,N]- acetylacetonatoiridium(III) [Ir(C6flq)2(acac)] have been demonstrated. The oligofluorene and [Ir(C6flq)2(acac)] show excellent solubility and processibility, with a device performance of 7.83+/-0.52 cd A(-1) and 3.30+/-0.10 lm W(1-) at 2479+/-45 cd m(-2) brightness with Commission International de L'Eclairage coordinates (0.66, 0.33). It was discovered that the efficiency can be further enhanced by exposing the finished organic thin film to a polar solvent or solvent vapor before deposition of the cathode contact. As a result, a peak efficiency of 12.20+/-0.16 cd A(-1) and 6.35+/-0.03 lm W(1-) at 1821+/-238 cd m(-2) brightness is achieved. This efficiency enhancement can be attributed to the presence of interface dipoles between the light-emitting layer and cathode contact.