Role of Molecular Orbital Energy Levels in OLED Performance

Abstract Abundant molecules enable countless combinations of device architecture that might achieve the desirable high efficiency from organic light-emitting diodes (OLEDs). Due to the relatively high cost of OLED materials and facilities, simulation approaches have become a must in further advancing the field faster and saver. We have demonstrated here the use of state-of-art simulation approaches to investigate the effect of molecular orbital energy levels on the recombination of excitons in OLED devices. The devices studied are composed of 1,1-bis(di-4-tolylamino)phenylcyclohexane (TAPC) as hole transporting material (HTM), 4,4′-Bis(9-carbazolyl)-1,1′-biphenyl (CBP) as host, 2,2',2”-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) or bathophenanthroline (Bphen) as electron transporting materials. The outcomes reveal that exciton recombination highly sensitive to the energy-level alignment, injection barriers, and charge mobilities. A low energy-barrier (10 6 times greater than that in the TPBi based device. The high carrier mobility of Bphen whose electron mobility is 5.2 × 10 −4 cm 2 V −1 s −1 may lead to low charge accumulation and hence high exciton dynamics. The current study has successfully projected an in-depth analysis on the suitable energy-level alignments, which would further help to streamline future endeavours in developing efficient organic compounds and designing devices with superior performance.