Optoelectronic properties of naphtho[2, 1-b:6, 5-b′]difuran derivatives for photovoltaic application: a computational study

Some important optoelectronic properties of naphtho[2,1-b:6,5-b′]difuran (DPNDF) and its two derivatives have been limelighted by applying the density functional theory (DFT). Due to their low cost, high stability and earth abundance, the DPNDF and its derivatives are considered as potential organic semiconductor materials for their optoelectronics applications. Highly proficient derivatives are obtained systematically by attaching –CN (cyanide) to DPNDF at various sites. Our calculations indicate that DPNDF has a wide and direct band gap with an energy gap of 3.157 eV. Whereas the band gaps of its derivatives are found to be decreased by 88 meV for derivative “a” and 300 meV for derivative “b” as a consequence of p orbitals present in C and N atoms in derivative structures. The narrowing of the energy gap and density of states for the derivatives of DPNDF in the present investigation suggest that energy gap can be engineered for desirable optoelectronic applications via derivatives designing. Furthermore, their obtained results for optical parameters such as the dielectric and conductivity functions, reflectivity, refractive index, and the extinction coefficients endorses their aptness for optoelectronic applications.

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Graphical Abstract Real part of dielectric function for derivative “b”

     

Structural and electronic properties of 4H-cyclopenta[2,1-b,3;4-b′]dithiophene S-oxide (BTO) derivatives with an S, S=O, O, SiH2, or BH2 bridge: semi-empirical and DFT study

In this paper, we theoretically studied the geometries, stabilities, and the electronic and thermodynamic properties of 4H-cyclopenta[2,1-b,3;4-b']dithiopene S-oxide derivatives (BTO-X, with X = BH(2), SiH(2), S, S=O, or O) using semi-empirical methods, ab initio methods, and density functional theory. The geometries and thermodynamic parameters calculated by PM3 were in good agreement with those calculated with B3LYP/6-31 G*. The band gap calculated using B3LYP/6-31 G* ranged from 3.94 eV (BTO-O) to 3.16 eV (BTO-B). The absorption λ(max) calculated using B3LYP/6-31 G* was shifted to longer wavelengths when X = BH(2), SiH(2), or S=O (due to their electron-withdrawing effects) and to shorter wavelengths for BTO-S and BTO-O as compared to the λ(max) for the thiophene S-oxide (2TO) dimer. The changes in ΔH°, ΔS°, and ΔG° calculated using both semi-empirical and DFT methods were quite similar.