Bond order effects on the optoelectronic properties of oxygen/sulfur functionalized adamantanes

The objective of this work, is to study adamantanes and to tune their bandgap, since pure adamantane is considered as an insulator due to its high bandgap energy. For this, we doped adamantane with oxygen and sulfur atoms, thus obtaining 730 different structures with double bonds and 730 different structures with single bonds, for a total of 1460 structures, and compared their properties. Among all, 31 molecules were selected that best represented the reduced bandgap behavior. The calculations with greater precision in its results were made using the Local Density Approximation (LDA), in the Density-Functional Theory (DFT) formalism, with PWC functional and TNP basis set. The electronic and optical properties were analyzed, by calculating the energy gap and absorption spectrum. Importantly, we observed that molecules doped with sulfur atoms (double bonds) had their energy gap reduced significantly compared to molecules doped with sulfur and/or oxygen atom with single bonds and pristine adamantane. It was found that in the absorption spectrum, the sulfur-doped structures had their spectrum shifted to the visible region, a fact that becomes relevant for potential dyes and optoelectronic applications. From the seven selected functionalized adamantanes (ADD-04, ADD-05, ADD-07, ADD-19, ADD-20, ADD-41, and ADD-48), any of these could be used as a dye. However, the ADD-20 molecule in particular, which presented optical absorption near (RGB) primary colors, could indicate a potential quantum dot material for application in developing screens of various electronic devices.