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This paper presents a device proposal based on a junction between an absorbing semiconductor nanorod structure and another window semiconductor layer for solar cell application. The possibility of band gap tuning by varying the diameter of the nanorods along the length, higher absorption coefficient at nanodimensions, the presence of a strong electrical field at the nanorod-window semiconductor nanojunctions and the carrier confinement in lateral direction are expected to result in enhanced absorption and collection efficiency in the proposed device. Process steps, feasibility, technological tasks needed for the realization of the proposed structure and the novelty of the present structure in comparison to the already reported nanostructured solar cells are also discussed. [Copyright &y& Elsevier]

This work reports the fabrication of zirconia thin films by e-beam deposition, followed by thermal annealing in air at different temperatures to optimize the cubic phase without using any dopants or chemical stabiliser. The X-ray diffraction (XRD) and Raman spectra of zirconia films annealed at 500 °C reveal the formation of stable cubic phase with a crystallite size of 10.7 ± 0.8 nm at room temperature. Optical transparency of the zirconia film annealed at 500 °C is high, approaching 80% in the visible range. Increasing annealing temperature improves crystallinity, hydrophilicity and reduces nonradiative associated defects. The mechanical properties of zirconia films examined using static and dynamic nanoindentation demonstrate that hardness increases from 7.60 ± 0.26 GPa to 11.08 ± 0.90 GPa and elastic modulus increases from 170.74 ± 4.98 GPa to 210.13 ± 5.56 GPa when annealing temperature increases. The post-annealing temperature influences provide a method for tuning the optical, wetting and mechanical characteristics of zirconia thin film. [ABSTRACT FROM AUTHOR]

The deposition of reduced graphene oxide over layer on the SnS thin films had been shown to be an effective tool to improve its photoelectrochemical response. Pure phase SnS thin films were prepared using simple and inexpensive thermal evaporation method on ITO glass substrate followed by the deposition of reduced graphene oxide (rGO) layer by drop cast method. Samples were characterized using X-ray diffraction, Raman, scanning electron microscopy, UV–Visible absorption spectroscopy and their photoelectrochemical activity has been investigated. The results show the formation of pure phase SnS having orthorhombic crystal structure with optical band gap of 2.0 eV, rGO layer enhances the absorption in visible region. Maximum photocurrent density exhibited by SnS/0.1 wt% rGO was observed to be 1.1 mA/cm2 as compared to pristine SnS (0.3 mA/cm2) at 0.95V Ag/AgCl with enhanced photostability up to 1 h. Graphene oxide over layer acts as protecting layer for SnS in the electrolyte and plays a promising role in enhancing the charge carriers separation at the interface on account of being an electron reservoir to accept the photoexcited electrons. This work highlights the role of rGO and SnS interface on the photoelectrochemical water splitting. • Phase pure SnS thin films were prepared by using a simple and cost effective thermal evaporation method. • Variation of rGO concentration played a significant role in PEC response. • Improved charge separation & enhanced PEC response was achieved in SnS/rGO samples in acidic medium. • SnS/0.1 wt % rGO sample exhibited the best PEC response in acidic medium. [ABSTRACT FROM AUTHOR]

Abstract Pulsed laser deposited thin films of Cu 2 SnS 3 (CTS) are characterized for the structural, electronic and optical properties using X-ray diffraction, Raman, UV–Vis-NIR spectroscopy, scanning electron microscopic techniques, and density functional theory. It is observed that thin-film samples annealed at low temperature have a metastable tetragonal structure, whereas the films annealed at 450 °C have a predominant stable monoclinic phase. A direct band gap of 1.1 eV, measured from the transmittance spectra, in close agreement with the theoretical band gap value of 0.89 eV obtained from density functional theory calculations. Optical properties reveal that CTS has a large absorption coefficient ~0.5 × 104 cm−1 at 1.5 eV which is comparable to other Cu S based materials like CuInS 2 and Cu 2 ZnSnS 4. The direct band gap and large absorption coefficient make CTS as one of the potential alternative absorber materials for thin-film solar cell applications. Highlights • Pulsed laser deposited Cu 2 SnS 3 films were studied experimentally and computationally • Low (high) temperature annealed films resulted tetragonal (monoclinic) structure • Measured band gap (1.1 eV) in close agreement with calculated (0.89 eV) gap • Direct nature of a bandgap leads to the large absorption coefficient in Cu 2 SnS 3 [ABSTRACT FROM AUTHOR]

• Synthesis of α- MoO 3 2D layers and thin films via pulsed laser deposition technique. • 2D layers show high gas sensing performance towards NO 2 as compared to the thin film. • p-type gas sensing behavior observed in 2D layers in contrast to n-type gas sensing behavior in thin film. • Sensor behavior is explained based on enhanced surface activity, oxygen vacancies, and metal- metal oxide contacts. In this study, α-MoO 3 two-dimensional (2D) layers and thin films were synthesized using pulsed laser deposition technique. X-ray diffraction and Raman spectroscopy confirm the formation of anisotropic α-MoO 3. Atomic Force Microscopy images show the evolution of morphology from 2D layers to oriented crystallite growth with increase in film thickness. Temperature and gas concentration dependent, gas sensing response has been observed to be quite different in 2D layers in comparison to thin film sample. 2D α-MoO 3 layers (∼ 6 nm) show higher response of about 25 % at a lower temperature (100 °C); They exhibit lower detection limits (up to 100 ppb) and selectivity towards NO 2 gas. Also, 2D layers show p-type gas sensing response and nonlinear current-voltage (I–V) characteristics of metal- metal oxide junctions, in complete contrast to thin film sample, which shows an n-type gas sensing response and linear I–V characteristics. The results have been explained on the basis of lower oxygen defect concentration, enhanced oxygen adsorption at the surface, and metal- α-MoO 3 contact favoring hole conduction. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) layered semiconducting materials, such as MoS 2 , SnS 2 and SnS, have received remarkable consideration due to their thickness dependent properties and potential applications. In this study, SnS and SnS 2 thin films were grown using a simple method of thermal evaporation and their possible application in photoelectrochemical splitting of water reaction have been investigated. X-ray diffraction, Scanning electron microscopy, Raman spectroscopy, and UV–Vis spectroscopy techniques results show the presence of SnS and SnS 2 pure phases with orthorhombic and hexagonal crystal structure, having band gap values of 1.8 eV and 2.75 eV, respectively. The photoelectrochemical response of as grown SnS and SnS 2 thin films was investigated and the results showed the photoanodic behaviour for SnS 2 films with photocurrent density of 1 mA cm−2 and photocathodic nature for SnS with photocurrent density of 0.4 mA cm−2 at 0.95 V vs. Ag/AgCl. The above obtained properties of SnS and SnS 2 opens a pathway for using these films for SnS–SnS 2 heterojunctions for further improving the photoelectrochemical response. • Phase pure SnS and SnS 2 thin films were prepared using thermal evaporation. • SnS 2 and SnS thin films show absorption in visible range. • Both SnS 2 and SnS displayed significant photoelectrochemical response. • SnS and SnS 2 exhibit p-type and n-type conductivity respectively. [ABSTRACT FROM AUTHOR]

• Cu-poor, Sn-rich stoichiometry indicates volatility of Sn across CZTS thin film. • EDX mapping in the CZTS shows a heterogeneous distribution of compositions. • Sulphurization process in CZTS thin film drives grain-grain boundary growth. In the present work, the Cu-poor and Sn-rich CZTS thin films were prepared in order to study the volatility of Sn with respect to other components. Thin film compositions were kept intentionally Sn-rich to understand the behaviour of loss and segregation of Sn during sulphurization. The homogeneous composition distribution in precursor thin films turns heterogeneous with a change in morphology after sulphurization. The inability of identifying nanoscale secondary phases in CZTS thin film by conventional analytical techniques such as XRD and Raman, can be fulfilled by employing HAADF-STEM analysis. XPS and HAADF-STEM analyses provide the quantification of nanoscale secondary phases across the thin film and surface, respectively. The volatility of Sn was revealed in the form of segregation in the middle layer of CZTS cross-sectional lamella rather than loss to annealing atmosphere. It was observed that among the cations of CZTS, Sn segregates more than Cu, while Zn segregates least. The nanoscale spurious phases were observed to vary across different regions in the sulphurized CZTS sample. The reactive annealing lead to grain growth and formation of grain boundary features in the CZTS thin films, where annealing significantly modifies the potential difference and band bending at grain boundaries with respect to intra-grains. [ABSTRACT FROM AUTHOR]