Electroluminescence of fluorescent–phosphorescent organic light-emitting diodes with regular, inverted, and symmetrical structures

• The emission of device with an inverted-EML was color-stable.
• A color-tunable white OLED was obtained when a compensated-EML was prepared.
• Device with a symmetrical-EML achieved an improvement in EL efficiency.

The influence of the device structure on the electroluminescence (EL) properties of fluorescent–phosphorescent organic light emitting diodes (OLEDs) was demonstrated. Four devices with regular-, inverted-, compensated- and symmetrical-emission layers (EMLs) were prepared. In regular-EML device, DCJTB emission increased when the phosphorescent sensitized EML was thickened. In inverted-EML device, low electron energy barrier at the Bphen/BCzVB interface resulted in weakened blue emission. The compensated-EML device, prepared with a red color-compensated layer, showed a color-tunable broadband white emission. Conversely, device with a quantum-like symmetrical-EML showed a narrow color-temperature range. Stable EL efficiency was obtained from regular, compensated, and symmetrical-EML devices. In contrast, EL efficiency of inverted-EML device rolled off significantly, though it had the highest EL efficiency of 11.4 cd/A.