Influence of the hole transport layer on spectral stability in the white phosphorescent organic light emitting diode with non-doped structure

In order to decrease the fabrication process complexity and improve the color stability, a series of two complementary colors white phosphorescent organic light emitting diodes (WOLED) are fabrication. The color stability of WOLED can be realized by increasing the thickness of the second hole transport layer (HTL2), which can weaken the hole mobility rapid raising with the increase of voltage and stabilize the recombination zone. The electroluminescence characteristic and color stability can be further improved by inserting ultrathin FIrpic emitting layer in HTL2. In device B1, the color coordinate (CIE1931) is (0.335 ± 0.003, 0.442 ± 0.002) while luminance changes from 100 cd/m2 to 5000 cd/m2, the maximum values of luminance, current efficiency and power efficiency can reach 5709 cd/m2, 29.65 cd/A and 19.62 lm/W, respectively.