Efficient co-doped white organic light-emitting diodes with high color stability and color rendering index

Efficient color-stable fluorescent white organic light-emitting diodes based on a blue fluorescent host 2-(t-butyl)-9,10-di(2-naphthyl)anthracene(TBADN) co-doped with a blue guest p-di(p-N,N-diphenyl-amino-styryl)benzene(DSA-ph) and a red guest 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran(DCJTB) were reported. The luminance mechanism was explored by analyzing the characteristics of devices with different doping concentrations. It was found that DSA-ph showed effective assistant energy transfer ability in the system. When 1.5% DSA-ph and 0.5% DCJTB were doped, the energy of the system could be most effectively utilized, achieving a maximum luminance efficiency of 14.26 cd/A at 40 mA/cm2, with a color rendering index of 80. The Commission International de L’Eclairage coordinates changed slightly from (0.3381, 0.3327) to (0.3336, 0.3203), as the applied current density increased from 20 mA/cm2 to 200 mA/cm2. The high efficiency could be attributed to effective utilization of host energy, as well as the depression of concentration quenching, and the color stability may be ascribed to the efficient energy transfer from host to both guests in direct and indirect ways and efficient exciton confinement.

► The assistant energy transfer mechanism was introduced to analyze the improvement of co-doped fluorescent WOLEDs.
► By analyzing the EL spectra of the devices, the PL and Abs spectra of the material, the assistant energy transfer mechanism was demonstrated to exist.
► The CIE coordinates was very stable, changing slightly from (0.3381, 0.3327) to (0.3336, 0.3203), as the current density increased from 20 mA/cm2 to 200 mA/cm2.
► A high current efficiency of 14.26 cd/A at 40 mA/cm2 was achieved.
► A color rendering index of 80 was achieved.