Anima Ghosh

Bandgap tuning in highly c-axis oriented Zn1−xMgxO thin films

We propose Mg doping in zinc oxide (ZnO) films for realizing wider optical bandgap in highly c-axis oriented Zn1−xMgxO (0 ≤ x ≤ 0.3) thin films. A remarkable enhancement of 25% in the bandgap by 30% Mg doping was achieved. The bandgap was tuned between 3.25 eV (ZnO) and 4.06 eV (Zn0.7Mg0.3O), which was further confirmed by density functional theory based wien2k simulation employing a combined generalized gradient approximation with scissor corrections. The change of stress and crystallite size in these films were found to be the causes for the observed blueshift in the bandgap.

Solution-processed Cu2XSnS4 (X = Fe, Co, Ni) photo-electrochemical and thin film solar cells on vertically grown ZnO nanorod arrays

This article presents the photo-electrochemical and photovoltaic performances of solution processed Cu2XSnS4 (X = Fe, Co, Ni) thin films on ZnS coated vertically aligned ZnO nanorod (NR) arrays for the first time. The optical, structural and electrical properties of all the synthesized structures were investigated using various characterization techniques. The electrocatalytic activities of the superstrate structures were characterized by taking cyclic voltammetry (CV) measurements and performing electrochemical impedance spectroscopy (EIS) analyses. Furthermore, the photovoltaic performances of the devices with architecture ITO/ZnO-NRs/ZnS/Cu2XSnS4/Au were investigated under AM 1.5 illumination condition. The thin film solar cells with Cu2FeSnS4 (CFTS), Cu2CoSnS4 (CCTS) and Cu2NiSnS4 (CNTS) photoactive layers exhibited power conversion efficiency (PCE) values of 2.73%, 3.23% and 2.71% respectively. All the devices exhibit good electrochemical as well as photovoltaic performance under illuminations and have shown potential to fabricate nontoxic solution processed high efficient devices.

Chemical synthesis, characterization and theoretical investigations of stannite phase CuZn2AlS4 nanocrystals

Stannite phase CuZn2AlS4 (CZAS) nanocrystals have been grown for the first time using hot injection and hydrothermal processes. As-synthesized nanocrystals in the shape of nanowires (from a hot injection process) and nanoplates (from a hydrothermal process) show band gaps of 1.64 eV and 1.69 eV, respectively, which is attractive for use as solar cell absorber materials. From first principles study, we find that CZAS exhibits direct band characteristics with a high absorption coefficient of >104 cm−1. Based on energy considerations the stannite structure is found to be more stable than the kesterite, wurtzite, orthorhombic and zinc blende type structures. The total and partial density of states (DOSs) indicate that hybridization between Zn-s and S-p like bands occurs near the Fermi level.

Photo-electrochemical properties and electronic band structure of kesterite copper chalcogenide Cu2–II–Sn–S4 (II = Fe, Co, Ni) thin films

Herein, we report a spin coating route for the deposition of multifunctional quaternary copper chalcogenide Cu2–II–Sn–S4 (II = Fe, Co and Ni) thin films on ITO glass substrates. The surface morphology of the thin films is a uniform porous like structure with an average film thickness of 1.5 μm. The formation of single phase Cu2FeSnS4 (CFTS), Cu2CoSnS4 (CCTS) and Cu2NiSnS4 (CNTS) thin films was confirmed by Raman spectroscopy, which reveals two principal Raman peaks of the A1 phonon mode. Due to the presence of the d6, d7 and d8 electronic configurations within Fe2+, Co2+ and Ni2+ ions, respectively, all the materials show a spin magnetic moment per ion of 3.33 μB, 2.45 μB and 1.31 μB for CFTS, CCTS and CNTS, respectively, as described by the electronic band structure calculation (WIEN2k code). All the thin films have estimated band gap values of 1.87 eV, 1.57 eV and 1.74 eV, respectively, with enhanced photocurrent properties and electrocatalytic activity. Significantly improved charge transfer properties of the thin films were observed from electrochemical impedance spectroscopy analysis under dark and visible light illumination conditions. These thin films are promising for use in photoelectrochemical and solar cell applications.

Correction to: Theoretical investigations on enhancement of photovoltaic efficiency of nanostructured CZTS/ZnS/ZnO based solar cell device

The original version of this article was published with the following errors. This has been corrected with this erratum.