| 초록 |
We fabricated devices with 2,2',2''-(pyrimidine-2,4,6-triyl)tris(N,N-diphenylaniline) (TPA-Pyr) and 2,2',2''-(1,3,5-triazine-2,4,6-triyl)tris(N,N-diphenylaniline) (TPA-Trz) for green phosphorescent organic light emitting diodes (PHOLEDs). These host materials have different donating and accepting moieties that is lead to bipolar character. TPA-Pyr has similar charge transport ability with TPA-Trz but the device with TPA-Pyr host has broad recombination zone, which can cause low efficiency roll-off. The TPA-Pyr device has 58.8 cd/A maximum current efficiency and 57.9 cd/A at 1000 cd/m2 but TPA-Trz device has 67.6 cd/A maximum current efficiency and only 48.4 cd/A at 1000 cd/m2. Even under the condition of 10000 cd/m2, current efficiency of TPA-Pyr decreased only 34.8% of maximum value but TPA-Trz decreased 65.8%. Low efficiency roll-off is resulted from broad recombination zone, which is identified by spectra of red sensing test. |
