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Quaternary chalcogenides based on stannite I-II $$_2$$ -III-VI $$_4$$ structure are the best potential candidates to overcome the current generation of solar harvesting materials. First-principles electronic structure simulations were performed on semiconducting CuZn $$_2$$ Ga(S/Se) $$_4$$ (CZGS/Se) to understand the inter-relationship of the structural properties. These structures contain a cubic close packing (ccp) array of S/Se-centered tetrahedrons, coordinated by one Cu, two Zn and one Ga atom occupying one half of the ccp tetrahedral voids. The remarkable variations in the crystal structures are explained by the influence of ionic radii of various atoms. The electronic and optical properties calculated using hybrid functional (Heyd, Scuseria and Ernzerhof, HSE06) show a suitable band gap of 1.59 eV for CZGSe with high optical absorption. The current density and maximum upper limit of theoretical energy conversion efficiency (P(%)) of CZGSe is enhanced when compared to that of CZGS. Our results suggest that the stannite CZGSe structure could be a promising candidate for efficient earth-abundant thin-film solar cell applications.

van der Waals (vdW) interaction-based heterostructures are known for enhanced photon absorption. However, the origin of these phenomena is not yet completely understood. In this work, using first-principles calculations, we provide a comprehensive study to show the effect of vdW interactions on the optical and electrical characteristics of the device and its origin. Herein, MoS2/2D (where 2D varies as graphene, black and blue phosphorene, and InSe) vdW heterojunctions are considered as model structures. The change in the band gap of the heterostructures is because of hybridisation and the non-linearity of the exchange-correlation functional. Hybridisation is correlated with strain and the difference in interstitial potential between layers of the heterostructure and the vacuum level. Significantly, the estimated values of energy conversion efficiency are high in the case of MoS2/InSe and MoS2/BlackP vdW heterostructures as compared to MoS2/GR and MoS2/BlueP, suggesting their potential application in efficient and atomically thick excitonic solar cell devices.

Carbon allotropes are known to be promising materials as chemical gas sensors. Proper modification in the electronic structure is required using suitable heteroatom doping to acquire better sensing property. We present the homonuclear B2 (B B) and B3 (B B B) doped carbon allotropes for the detection of toxic gases such as NO2, CO2, NH3, H2S and CO using the density functional theory. The sensitivity and selectivity of pure and boron doped C60 surfaces towards toxic gas molecules are estimated. With a new perception, the gas sensitivity has been correlated with π electron occupancy of the host materials. The adsorption behaviour of toxic gases on the host surface during the presence of H2O, O2 and O molecule/atom is estimated. The concept of homonuclear B sites is extended to 585 divacancy graphene and 585 divacancy carbon nanotube (CNT) system and verified that the phenomena are general for sp2 hybridized carbon allotrope. We also tested the CO oxidation and CO2 hydrogenation on B2 and B3 doped: C60 cage, 585 DV graphene and 585 DV CNT. The CO oxidation occurs via Langmuir–Hinshelwood (LH) mechanism. Overall we have found that the presence of homonuclear bond can change the inert carbon allotropes into highly active sensor material.

van der Waals (vdW) interaction-based heterostructures are known for enhanced photon absorption. However, the origin of these phenomena is not yet completely understood. In this work, using first-principles calculations, we provide a comprehensive study to show the effect of vdW interactions on the optical and electrical characteristics of the device and its origin. Herein, MoS

The earth abundant and non-toxic solar absorber material kesterite Cu2ZnSn(S/Se)4 has been studied to achieve high power conversion efficiency beyond various limitations, such as secondary phases, antisite defects, band gap adjustment and microstructure. To alleviate these hurdles, we employed screening based approach to find suitable cationic dopant that can promote the current density and the theoretical maximum upper limit of the energy conversion efficiency (P(%)) of CZTS/Se solar devices. For this task, the hybrid functional (Heyd, Scuseria and Ernzerhof, HSE06) were used to study the electronic and optical properties of cation (Al, Sb, Ga, Ba) doped CZTS/Se. Our in-depth investigation reveals that the Sb atom is suitable dopant of CZTS/CZTSe and also it has comparable bulk modulus as of pure material. The optical absorption coefficient of Sb doped CZTS/Se is considerably larger than the pure materials because of easy formation of visible range exciton due to the presence of defect state below the Fermi level, which leads to an increase in the current density and P(%). Our results demonstrate that the lower formation energy, preferable energy gap and excellent optical absorption of the Sb doped CZTS/Se make it potential component for relatively high efficient solar cells.