Using non-equilibrium Green’s function density functional theory and natural bond orbitals techniques, the electrical conductance and physical description of two stilbene and TCAB molecular optical devices were investigated. The aforementioned molecules as molecular optical devices are capable to have two forms, switching between their trans and cis iso-mers, in response to heat or UV–visible light. The results of the investigation were dis-cussed by the structure of molecular configuration’s forms, adsorption types (top, bridge, and hollow), rectification ratios, transmission spectra, PDOS, hyper conjugative ener-gies, and the orbital’s contributions. As a result, resistance changed from a low to a high conductive state when the molecular optical devices were switched in terms of trans–cis isomerization. The results show, the efficiency of device, on–off ratio, in the TCAB is less than that in Stilbene. In Stilbene -CH = CH– group substituted instead of –N = N– group in azobenzene, as parent molecule of TCAB.

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