INTRODUCTIONOrganic light emitting diodes (OLEDs) have been discovered by Tang and Van Slyke [1,2]. Since then, they have been the center of studies around the globe because of their important applications in full-colour displays and lighting sources. Nowadays organic light emitting diodes (OLED) applications cover wide range of displays such as mobile phones, TV, notebooks, tablets, digital cameras and automotives. Organic lightemitting diodes have the advantage to make full colour largeflat-panel displays on low-cost flexible substrates [3]. OLED device can be made of organic hole-and electron-transporting layer sandwiches between two metal electrodes. Comparing with hole-transporting materials, a few good electron-transporting materials (ETMs) were reported. ETMs have outstanding electron transporting properties that are required to improve the efficiency of OLED devices [4]. Benzimidazole derivatives as electron transporting materials with highly efficient OLED device were reported [5]. Benzimidazole and its derivatives showed different fluorescence efficiencies, based on their molecular structures. Therefore, designing of new materials based on changing the molecular structure is the suitable way for the invention of Asian Journal of Chemistry; Vol. 29, No. 10 (2017), 2259-2270 novel efficient materials [6]. Recently, several studies have been reported on the influence of changing the linking modes in the chemical structure of the benzimidazole compounds and their effect on the thermal, photophysical, electrochemical and charge transport properties [7]. The purpose of this article is to use the computational calculations based on density functional theory (DFT) to study the effect of the substituents on 2-(5,6-dihydrobenzimidazo[1,2-c]quinazolin-6-yl)-5-substituted phenol and to investigate their properties as charge transporting materials to improve design and performance of OLED devices.COMPUTATIONAL METHODS Molecular electronic structure calculations were performed using the density functional theory (DFT) and time dependentdensity functional theory (TD-DFT). The DFT calculations were done by Becke's three-parameter exchange functional with Lee-Yang-Parr (LYP) correlation functional. Gaussian 09 software [8] were used to performed full geometry optimizations of substituted phenol; L-H, L-Br, L-OCH3 at the B3LYP level of theory using an 6-31++G(d,p) basis set. The optimization was confirmed with absence of negative frequency. The optimized geometries were then employed to calculate UV-visible