||Recently, bipolar hosts have aroused considerable interests in the phosphorescent organic light-emitting diodes (ph-OLEDs). The ph-OLEDs utilizing bipolar hosts usually exhibit better device performance benefiting by the balance of electron and hole fluxes. The simplified structure also reduces production cost efficiently.|
In this thesis, we reported a series of pyrrole derivatives for bipolar host materials, which exhibit bipolar carrier transport properties as host materials for ph-OLEDs.
Both green and red-emitting ph-OLEDs were demonstrated in the thesis. In the study of green-emitting ph-OLEDs, the device configuration with the best performance was ITO/α-NPB (35nm)/ppn:16% ir(ppy)3( 30nm)/Bphen (44nm)/ LiF(0.5nm)/Al(130nm).
The maximum brightness, current efficiency, and power efficiency of the device was 13419cd/m2, 3.16 cd/A, and 1.34 lm/W, respectively.
In the study of red-emitting phOLEDs, the device configuration with the best performance was ITO/TAPC(35nm)/ppn:2%ir(pq)2acac(30nm)/Bphen(44nm)/LiF(0.5nm)/Al(130nm).The maximum brightness, current efficiency, and power efficiency of the device was 42648 cd/m2,12.4 cd/A, and 10.2 lm/W, respectively.
Such high power efficiency in the simplified device structure shows great potential of the bipolar host, ppn, in the application of deep-red ph-OLEDs.
Finally, white OLEDs with the configuration of ITO/TAPC (35nm)/ mcp:7% firpic (10nm)/ppn:2% ir(pq)2acac(10nm)/ mcp:7% firpic(10nm)/Bphen(44nm) /LiF(0.5nm)
/Al(130nm) was demonstrated. The current efficiency and CIE 1931 color coordinates of the device was 7.80 cd/A and (0.37,0.37) , respectively .The results indicate that the device is suitable for display or lighting applications.