Improvement of FWHM and luminance of blue organic light-emitting diodes with double hole-blocking structure

A blue organic light-emitting diode (OLED) with a double hole-blocking structure (DHB) has been developed. The device, ITO/m-MTDATA/NPB/(BCP/NPB/BCP)/Alq3/LiF/Al, consists of a hole-injection layer, a hole-transporting layer, a DHB structure layer and an electron-transporting layer. The NPB functions as the hole-transporting emitter layer, while the BCP/NPB/BCP structure is the hole-blocking emitter layer. This BCP/NPB/BCP (DHB) structure has successfully improved the color purity by a 20% reduction in the full-width at half-maximum (FWHM) for the 25 °C EL spectra, and nearly doubled the luminance (1025 cd/m2) of the device at 170 mA/cm2.