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Indium selenide (γ-In2Se3) films were prepared using RF magnetron sputtering. Influence of deposition time on structural, optical, morphological, and photoelectrochemical (PEC) performance was studied. Formation of γ-In2Se3 is confirmed by low angle XRD, Raman spectroscopy, and XPS analysis. Surface morphology investigated using FE-SEM shows that γ-In2Se3 films are uniform and have a dense grain structure, without cracks and holes. Optical properties show that γ-In2Se3films absorb mainly in the UV region, and the bandgap energy decreases from 2.81 to 2.27 eV as deposition duration increases. Conduction and valance band-edge potential values show that γ-In2Se3 films are suitable for photoelectrochemical hydrogen evolution. PEC activity of γ-In2Se3 photoanodes was evaluated using linear sweep voltammetry (LSV), and there was an increase in photocurrent density with deposition time. Electron impedance spectroscopy (EIS) analysis revealed that γ-In2Se3 photoanodes had high charge transfer resistance, and it decreases with deposition time, which leads to improved PEC performance. Investigation of Mott Schottky's (MS) results shows a shifting of flat band potential towards negative potential, suggesting movement of fermi level towards conduction band edge. Carrier density increases from 3.7 × 1019 cm−3 to 8.9 × 1020 cm−3 and depletion layer width of γ-In2Se3 photoanodes are found in the range of ~ 2.67–9.10 nm. The gradual increase in electron lifetime indicates a decrease in the recombination rate of photo-generated charge carriers. An increase in time-dependent photocurrent density reveals that γ-In2Se3 films have effective electron–hole separation. Our work demonstrates that γ-In2Se3 can be a probable candidate for PEC water splitting and opto-electronic applications. [ABSTRACT FROM AUTHOR]

Zinc oxide nano-sheets (ZNS) loaded with Zeolitic Imidazole Framework 8 (ZIF8) nanocrystals, i.e. (ZNS@ZIF8) thin films, were successfully synthesized using electrodeposition and facile chemical bath deposition (CBD) for photoelectrochemical (PEC) splitting of water. The formation of ZNS nano-sheets and ZIF8 nano-crystals has been confirmed by field emission scanning electron microscopy (FE-SEM), low angle X-ray diffraction (XRD), micro-Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy analysis. PEC activity of ZNS@ZIF8 photoanodes was evaluated using the linear sweep voltammetry (LSV) technique, and the photocurrent density is significantly enhanced when ZNS are decorated with ZIF8 nanocrystals. Electrochemical impedance spectroscopy (EIS) revealed that ZNS@ZIF8 had low charge transfer resistance compared to pristine ZNS counterparts. This led to considerably improved PEC performance of ZNS@ZIF8. Mott–Schottky (M–S) analysis of ZNS and ZNS@ZIF8 revealed a shift of flat band potential for the ZNS and ZNS@ZIF8 photoanodes, respectively. The shift of flat band potential indicates a clear shift in the Fermi level towards the conduction band, leading to an efficient charge transfer process across the electrolyte. The carrier density of ZNS and ZNS@ZIF8 photoanodes increases from 3.67 × 1019 cm−3 to 4.11 × 1020 cm−3. The enhanced applied bias photon conversion efficiency (ABPE) of ZNS@ZIF8 photoanodes suggests that ZNS@ZIF8 can be a prospective candidate for PEC and optoelectronic applications. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of highly stable, Pb-free bismuth iodide (BiI3 or BI), stoichiometric methylammonium bismuth iodide [(CH3NH3)3Bi2I9 or MA3Bi2I9 or s-MBI] and non-stoichiometric methylammonium bismuth iodide [(CH3NH3)2BiI5 or MA2BiI5 or Ns-MBI] perovskite thin films for photodetector applications. These films are synthesized at room temperature by a single step solution process spin coating method. The structural, optical, and morphological properties of these films were investigated using different characterization techniques such as XRD, Raman spectroscopy, FE-SEM, UV-Visible spectroscopy, etc. Formation of BI, s-MBI and Ns-MBI thin films is confirmed by XRD and Raman spectroscopy measurements. XRD analysis reveals that BI has a hexagonal crystal structure and a P63/mmc hexagonal space group for s-MBI and Ns-MBI. The optical properties of BI thin films show a high absorption coefficient (∼104 cm−1) and a band gap of ∼1.74 eV. Similarly, s-MBI films have a high absorption coefficient (∼103 cm−1) and an indirect band gap of ∼1.8 eV. Moving from s-MBI to Ns-MBI, the value of absorption coefficient is ∼103 cm−1 and the band gap corresponds to ∼2 eV. Finally, photodetectors based on the synthesized BI, s-MBI and Ns-MBI perovskites have been directly fabricated on FTO substrates. All photodetectors exhibited highly stable photo-switching behaviour along with excellent photoresponsivity and detectivity, with a fast response and recovery time. Our work demonstrates that Pb-free BI, s-MBI and Ns-MBI perovskites have great potential in the future for realizing stable photodetectors. [ABSTRACT FROM AUTHOR]

In this paper, we report the effect of sulfur (S) substitution with selenium (Se) in CZTS nanocrystals prepared by hot injection method. The formation of kesterite-copper zinc tin sulfide (Cu2ZnSnS4, CZTS) and copper zinc tin selenide (Cu2ZnSnSe4, CZTSe) nanocrystals is confirmed by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) analysis. The XRD, TEM and atomic force microscopy (AFM) analysis shows an overall increase in average crystallite size upon Se substitution. AFM images revealed an increase in root mean square surface roughness (Sq) and average surface roughness (Sa) when S in CZTS is replaced by Se. The substitution of S by Se in host CZTS narrows the optical band gap from 1.56 to 1.03 eV. The ultraviolet photoelectron spectroscopy (UPS) analysis shows shift in valence band and conduction band edge in CZTSe compared to CZTS. The photocurrent density measurement in synthesized CZTSe thin films is ~ 4 to 5 times higher than CZTS thin films. The obtained results show that CZTSe can be a promising candidate as absorber material in photovoltaic applications. [ABSTRACT FROM AUTHOR]

• Synthesis of γ-In 2 Se 3 films and photodetectors on ITO-coated interdigital electrodes. • Investigation of annealing temperature effect on physical and sensing properties. • Confirmation of γ-In 2 Se 3 by XRD, Raman spectroscopy and XPS. • Highly stable photodetector with fast response (0.22 s) and recovery time (2.85 s). • γ-In 2 Se 3 photodetector can be a promising device for photodetection applications. Metal chalcogenide-based photodetectors have been studied extensively in recent years. However, the dark current, detective spectral ranges, responsivities, and response time are still unsatisfactory. Also, the major challenge for photodetector material is the deposition of large-scale material, a high-quality film with high reliability and low variability. In this work, we have synthesized Indium selenide (γ-In 2 Se 3) thin films using the RF magnetron sputtering technique. We have thoroughly investigated the effect of annealing temperature on structural, optical, morphological, and photo-sensing properties of the synthesized thin films. Low angle XRD confirms the formation of hexagonal γ-In 2 Se 3 films. The crystallite size increases from 56 nm to 64 nm with an increase in annealing temperature. Raman spectroscopy and XPS techniques confirm the γ phase of indium selenide. FE-SEM analysis revealed that the synthesized films are compact and uniform. Also, they are free from holes and cracks, which is necessary for semiconductor applications. The agglomeration of particles is observed with an increase in annealing temperature. The EDS spectra revealed that synthesized γ-In 2 Se 3 films have ideal stoichiometry with In:Se ratio of 2:3. The UV–visible spectroscopy analysis showed a slight decrease in bandgap from 2.0 eV to 1.93 eV with an increase in annealing temperature. Other optical properties, such as absorption coefficient (α), extinction coefficient (k), the real and imaginary part of dielectric constant, optical conductivity, etc., of synthesized γ-In 2 Se 3 films critically depend on the annealing temperature. Finally, the synthesized γ-In 2 Se 3 thin films were used to fabricate photodetectors on ITO-coated interdigital electrodes. All γ-In 2 Se 3 photodetector shows good stability and repeatability under dark and illumination conditions. The rise and decay time decrease with increase in annealing temperature. Photodetector with γ-In 2 Se 3 thin film annealed at 300 °C exhibited excellent photoresponsivity (1.12 mA/ W) and stable photoswitching behavior. A fast rise (0.22 s) and decay time (2.85 s) were observed for the prepared photodetector. Our work demonstrates that γ-In 2 Se 3 photodetector can be a promising material for photodetection applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon functionalized bismuth vanadate (BVO) photoanodes were synthesized using simple wet chemical process. To ascertain and determine various aspects of synthesized photoanodes, different types of characterization and measurements such as, X-ray Diffraction (XRD), Field emission scanning electron microscope (FE-SEM), UV–Visible (UV–Vis), Raman, Photoelectrochemical (PEC), Mott-Schottky (MS), and Electron Impedance Spectroscopy (EIS) have been carried out. Carbon functionalized BVO (C-BVO) photoanodes demonstrated superior photoconversion efficiency (η∼0.38%) and short circuit current (J SC ∼0.50 mA/cm2 at 0.5 V vs. SCE) compared to pristine BVO. Bare BVO based PEC OR and AND logic gates have also been designed using pulsed white light beams. The PEC response reveals that for a white light beam with peak pump intensity of 100 mW/cm2, a photocurrent density of 83 μA/cm2 is generated at a bias of ∼0.5 V vs. SCE. Moreover, by tuning bias the photocurrent response can be inverted and further utilized to realize different logic operations simultaneously. The present study paves a new way for bismuth vanadate-based PEC computing devices. • Prepared carbon doped bismuth vanadate using simple wet chemical process. • Carbon functionalized BVO photoanodes demonstrated superior photoconversion efficiency (η ∼ 0.38%). • Designed bare BVO based photoelectrochemical OR and AND logic gates. • Inversion of photocurrent response by tuning bias. • Present study paves a new way for BVO-based PEC computing devices. [ABSTRACT FROM AUTHOR]

In this paper we report synthesis of highly conducting and optically transparent indium tin oxide (ITO) films with high charge carrier mobility using radio frequency (RF) magnetron sputtering without any post-annealing treatment. All deposited films show high optical transmittance in the visible region (> 85%) and the band gap ~ 3.54 eV. Based on the x-ray diffraction, atomic force microscopy, scanning electron microscopy and Hall measurement analysis the influence of RF power on ITO crystal growth mechanism have been discussed. It has been observed that with increasing RF power the preferred crystal orientation in films changes from (222) to (400) direction. A significant increase in charge carrier mobility have been observed with change in crystal orientation from ~ 45 cm2 V−1 s−1 in (222) direction to ~ 380 cm2 V−1 s−1 in (400) direction. At optimized RF power (90 W), ITO film with maximum figure of merit (φ TC = 150×10−3 Ω−1) with high optical transparency (~ 94%) and high conductivity (2.8 × 103 Ω−1cm−1) have been obtained. We believe that employment of such high mobility and high figure of merit ITO films can have potential applications in various opto-electronic devices such as smart windows, gas sensors, solar cells, light spreading electrode in light emitting diodes and organic light emitting diode displays. [ABSTRACT FROM AUTHOR]