Abstract
In the thesis, we used PPyP, PTP, TPyP, TTP as host materials doped with BCzVBi, TSTA, DPASP, and DMASP repectively, for the blue fluorescent emitters. With the suitable transporting materials and device layers, we have developed the deep-blue OLEDs with highly electrolu-minescence efficiency and long operation lifetime. Because the quantum yields of PPyP, PTP and TTP film doped with BCzVBi are above 90 % and TPyP film is also almost 90 %, energy transfer between host and dopant is efficient. Extraordinary external quantum efficiency (E.Q.E.) above 10 % is achieved in the device hosted by PTP, especially the DPASP-doped device 1T, showing the maximum E.Q.E. of 11.4 %, the current efficiency of 17.5 cd/A and the power efficie-ncy of 12.8 lm/W, the maximum luminescence of 91058 cd/m2, with the CIE coordinates of (0.14, 0.19). From the transient EL spectrum, we found that PTP-based devices showed the microsecond-scale delayed fluor-escence. Two triplet excitons formed a singlet exciton via triplet-triplet annihilation among excited PTP molecules, and singlet excitons were transfer to dopant for efficient delayed fluorescent. However, this is not the crucial reason why the E.Q.E. of device 1I、1P-1R exceeded the limited efficiency of fluorescent OLEDs. From the angle dependent p-polaried PL spectrum, the measurement reveals the transition dipole moments of the host materials doped with 5 % BCzVBi emitter is almost horizontal with a horiaontal factor ? of above 0.85, resulting in the increa-seing of the light-outcoupling factor, and the enhancement of the E.Q.E. exceeding the limited efficiency of fluorescent OLEDs. By using PPyP doped with 5 % DMASP as emission layer, HAT-CN doped with 5 % MoO3 as the p-typed HIL, Bebq2:Liq = 3:7 as the n-typed ETL, the device 2T structure increased of the device stability, resulting in the longer lifetime of 13515 hours (L0 = 500 nits) with the CIE coordinates of (0.15, 0.21), and the device showed the maximum E.Q.E. of 6.7 %, the current efficiency of 19.6 cd/A and the power efficiency of 11.7 lm/W. The TSTA-doped device 2U also had the lifetime of 12586 hours (L0= 500 nits) with the deeper blue CIE coordinates of (0.14, 0.18), and the device showed the maximum E.Q.E. of 7.8 %, the current efficiency of 15.0 cd/A and the power efficiency of 12.1 lm/W.