Effect of triplet multiple quantum well structures on the performance of blue phosphorescent organic light-emitting diodes
- Equal contributors
1 Department of Information Display, Hongik University, Seoul, 121-791, South Korea
2 Department of Chemistry, Sungkyunkwan University, Suwon, 440-746, South Korea
3 School of Display Engineering, Hoseo University, Asan, 336-795, South Korea
Nanoscale Research Letters 2012, 7:23 doi:10.1186/1556-276X-7-23Published: 5 January 2012
We investigate multiple quantum well [MQW] structures with charge control layers [CCLs] to produce highly efficient blue phosphorescent organic light-emitting diodes [PHOLEDs]. Four types of devices from one to four quantum wells are fabricated following the number of CCLs which are mixed p- and n-type materials, maintaining the thickness of the emitting layer [EML]. Remarkably, such PHOLED with an optimized triplet MQW structure achieves maximum luminous and external quantum efficiency values of 19.95 cd/A and 10.05%, respectively. We attribute this improvement to the efficient triplet exciton confinement effect and the suppression of triplet-triplet annihilation which occurs within each EML. It also shows a reduction in the turn-on voltage from 3.5 V (reference device) to 2.5 V by the bipolar property of the CCLs.