Organic Light-Emitting Diodes(OLEDs)

Organic light emitting diodes (OLEDs) are solid state light emitting devices where the emissive material is a thin film of organic semiconductor. OLED holds the fabrication advantage with flexible and stretchable substrates which cannot be achieved using inorganic emitters.  The organic emitters have classified according to their molecular weight, namely small molecule OLED or polymer LEDs. Since, the demonstration of first hetero-junction organic LED by Tang et al. in 1987, the efficiency of OLEDs now reached similar to nitride based LEDs. The conjugated π-electron conductivity and strong exciton confinement are some of the fruitful properties of organic emitters for realizing efficient light emission. By cultivating both singlet and triplet excitons in organics, it is possible to achieve 100% internal quantum efficiency. However, the maximum external quantum efficiency demonstrated in state of the art devices are 30-40% only. Significantly, the OLED performances are critically depends the on the charge balance and exciton confinement capabilities within the device architecture. In our research, we significantly focused  on the charge balance, exciton confinement and interface band alignment in OLEDs through different strategies.

References: 

1) P. Justin Jesuraj, Hassan Hafeez, Dong Hyun Kim, Jong Chan, Won Ho Lee, Dae Kuen Choi, Chul Hoon Kim, Myungkwan Song, Chang Su Kim and Seung Yoon Ryu, "Recombination Zone Control without Sensing Layer and the Exciton Confinement in Green Phosphorescent OLEDs by excluding Interface Energy Transfer", Journal of Physical Chemistry C,  Vol. 122 (2018) 2951−2958.

2) Sang Ho Rhee, Sung Hyun Kim, Hwang Sik Kim, Jun Young Shin, Jeeban Bastola and Seung Yoon Ryu, "Heavily Doped, Charge-Balanced Fluorescent Organic Light-Emitting Diodes from Direct Charge Trapping of Dopants in Emission Layer", ACS Applied Materials & Interfaces,  7 (2015) 16750−16759.

Display Convergence, Division of Display and Semiconductor Physics, College of Science and Technology,  Korea University Sejong Campus

2511 Sejong-ro, Sejong City, 339-770, Republic of Korea