Molecular designing and structural tuning of derivatives of 4,7-divinyl-1H-benzo[b]silole for optoelectronic properties using DFT and TD-DFT methods

4,7-divinyl-1H-benzo[b]silole (DVBS) and some of its derivatives have been designed and studied using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods to explore their optoelectronic properties. The present work examined the effects of substitution of donor–acceptor groups at the 4th and 7th positions of DVBS derivatives on their optoelectronic features, such as orbital energy gap (ΔE), NLO (nonlinear optical) properties, charge injection and transport properties, and excited state properties. Hence, the aim of the present work is to design small molecular DVBS derivatives and to examine their optoelectronic properties suitable for optoelectronic applications. Six of the seven DVBS candidates investigated appeared to be promising optoelectronic materials because of their narrower band gap (ΔE), higher hyperpolarizability (β), lower electron reorganization energy ( \({\uplambda }_{\rm{e}}\) ${\mathrm{\lambda }}_{\mathrm{e}}$ ), higher electron transport rate ( \({K}_{\rm{e}})\) $K_{\mathrm{e}})$ , longer absorption/emission maxima \(({\uplambda }_{\rm{max}}^{\rm{abs}}/{\uplambda }_{\rm{max}}^{\rm{em}})\) $({\mathrm{\lambda }}_{\max }^{\mathrm{abs}}/{\mathrm{\lambda }}_{\max }^{\mathrm{em}})$ , and higher oscillator strength (ƒ) than benzosilole designed so far, and it shows better electron transport and optoelectronic properties, suitable for optoelectronic applications. Particularly, the c2 candidates have lower ΔE (2.758 eV), larger β (1758.16 × 10^–30 esu), lower \({\uplambda }_{\rm{e}}\) ${\mathrm{\lambda }}_{\mathrm{e}}$ (0.108 eV), higher \({K}_{\rm{e}}\) $K_{\mathrm{e}}$ (6.66 × 10¹⁴ s⁻¹), lower excitation/emission energy( \({{E}}_{{\rm{abs}}}\) $E_{\mathrm{abs}}$ =2.638 eV/ \({{E}}_{\rm{em}}\) $E_{\mathrm{em}}$ =2.505 eV), longer absorption and emission maxima \(({\uplambda }_{\rm{max}}^{\rm{abs}}\) $({\mathrm{\lambda }}_{\max }^{\mathrm{abs}}$ =470 nm/ƒ = 2.3326 and \({\uplambda }_{\rm{max}}^{\rm{em}}\) ${\mathrm{\lambda }}_{\max }^{\mathrm{em}}$ =495 nm/ƒ = 3.1745). Hence, c2 has promising optoelectronic properties suitable optoelectronic applications.