Chromatic-stability white organic light emitting diodes based on phosphorescence doped electron transport layer

• Color-stability OLED was fabricated with Ir complex-doped electron transport layer.
• Ir(ppy)3-doped organic layer utilize excess holes to promote carrier balance.
• Ir(ppy)3-doped organic layer reduce electron-transport ability to promote carrier balance.
• The highest current efficiency is 37.4 cd/A.
• Efficiency roll-up arises instead of traditional roll-off phenomenon.

The influence of fac-tris(2-phenylpyridine)iridium [Ir(ppy)3] doped into electron transport layer was investigated by a series of electron-only devices, and the mechanism of the reduced field-dependent electron-transporting properties was also discussed. Utilizing the method of optimized doping concentration, a hybrid white organic light emitting diode with high efficiency, low efficiency roll-off and stable spectra was fabricated. Organic layer doped Ir(ppy)3 serves two functions: emit supernumerary green light with excess holes when the applied bias are low; weaken electron-transport ability when the bias increase. Both the two functions can improve the carrier balance and confine the exciton recombination region. For Device B, the maximum current efficiency and power efficiency reach 37.4 cd/A and 28.6 lm/W, respectively. The Commision Internationale de l’Éclairage (CIE) coordinates vary slightly from (0.48, 0.43) at 1.1 cd/m2 to (0.46, 0.43) at 18,600 cd/m2.