Driving characteristics of poly(N-vinylcarbazole) and 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3-4-oxadiazole-based polymer light emitting diodes

초록

We studied the driving characteristics of Poly(N-vinylcarbazole) (PVK)-based polymer light emitting diodes (PLEDs) by incorporating various 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3-4-oxadiazole (PBD) concentrations. PVK (M-n=25,000 similar to 50,000 g/mol) and tris(2-(4-tolyl)phenylpyridine)iridium (Ir(mppy)(3)) were used as the host and dopant materials, respectively. The transient electroluminescence (EL) of the PLED measurement was used to analyze the characteristics of the carrier transport by synchronizing the DC-pulse generator (10 V, 70 Hz) and photodiode. Among the fabricated PLEDs including those with different PBD concentrations from 0% to 60%, the devices with 60% PBD concentration showed the highest efficiency (15.5 cd/A) at 1000 cd/m(2). By increasing the PBD concentration, a shorter rising time of the PLEDs was achieved possibly due to improved transport behavior of the electrons by the PBD incorporation. This result is well agreement with the increased device efficiency by increasing the PBD concentration, which shows that the transient EL measurement can be a good method for analyzing PLED performance and charge balancing.

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