Interface Exciplex Anchoring the Color Stability of Solution-Processed Thermally Activated Delayed Fluorescent White Organic Light-Emitting Diodes

Spectral stability and high color rendering index (CRI) remain challenges to high-performance, solution-processed white organic light-emitting devices (WOLEDs) based on two complementary colors. The solution-processed WOLED based on two thermally activated delayed fluorescence emitters with complementary color, i.e., the orange-red 2-[4-(diphenylamino) phenyl]-10,10-dioxide-9H-thioxanthen-9-one emitter and the blue 4,4'-bis(carbazol-9-yl)-2,2'- dimethylbiphenyl: 4,6-bis(3,5-di(pyridin-4-yl) phenyl)-2-phenylpyrimidine interface exciplex, is reported here. Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)) diphenylamine)] is doped with 30 wt% cross-linkable N, N'-(4,4'-(cyclohexane-1,1-diyl) bis(4,1-phenylene)) bis(N-(4-(6-(2-ethyloxetan-2-yloxy)hexyl)phenyl)-3,4,5-trifluoroaniline) to form a smooth hole transportation layer with outstanding solvent resistance ability and efficient hole transporting/injection ability. The position of interface exciplex and exciton management in the emitting layer can be tuned, thus anchoring the color stability. The device displays a maximum external quantum efficiency of 10.02% and a high CRI of 85 with Commission Internationale de l'Eclairage (CIE) color coordinates of (0.32, 0.33) at the luminescence of 1000 cd m(-2). These results are among the best of solution-processed WOLEDs based on two complementary chromophores.