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Background: Transition from fetal to extra uterine circulation is a poorly understood process in terms of cerebral hemodynamics. Postnatal cerebral circulation and autoregulation is affected by the degree of prematurity and fetal hypoxia. Currently, the data on changes in postnatal cerebral blood flow indices in preterm and SGA neonates is limited. Objective: To investigate the differences between cerebral hemodynamics between preterm (28 0/6- 34 6/7) small for gestational age (SGA) and appropriate for gestational age (AGA) neonates. Methodology: In this prospective cohort study done in a tertiary care centre of South India in the year 2020-2021, we compared cerebral function parameters as assessed by doppler sonography between hemodynamically stable SGA (n = 57) and AGA neonates (n = 91) admitted to the NICU during the first 72 hours. Results: Preterm SGA neonates have significantly lower pulsatility index (PI) and resistive index (RI) in middle cerebral artery on day 2 and day 3. On day 2, the median (IQR) PI was 1.05 (0.91-1.98) vs 1.26 (1.10-1.39), p=0.002 and mean ± SD RI of 0.67 ± 0.09 vs 0.71 ± 0.08, p=0.01 and on day 3 median (IQR) PI was 1.12 (1.01-1.32) vs 1.28 (1.10-1.51), p=0.05 and mean ± SD RI of 0.68 ± 0.08 vs 0.72 ± 0.10 (p = 0.01) in SGA and AGA neonates respectively. Conclusion: SGA neonates have significantly lower indices of cerebral perfusion as seen by low PI and RI in MCA (middle cerebral artery) as compared to their AGA counterparts.

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.

Objective: Herein, we report the effect of variation of hydrogen flow rate on the properties of Si:H films synthesized using PE-CVD method. Raman spectroscopy analysis show an increase in crystalline volume fraction and crystallite size implying that hydrogen flow in PE-CVD promotes the growth of crystallinity in nc-Si:H films with an expense of a reduction in deposition rate. Methods: FTIR spectroscopy analysis indicates that hydrogen content in the film increases with an increase in hydrogen flow rate and hydrogen is predominantly incorporated in Si-H2 and (Si-H2)n bonding configuration. The optical band gap determined using E04 method and Tauc method (ETauc) show an increasing trend with an increase in hydrogen flow rate and E04 is found higher than ETauc over the entire range of hydrogen flow rate studied. Results and Conclusion: We found that the defect density and Urbach energy increases with an increase in hydrogen flow rate. Photosensitivity (σPhoto /σDark) decreases from ~103 to ~1 when hydrogen flow rate is increased from 30 sccm to 100 sccm and can be attributed to amorphous-to-nanocrystallization transition in Si:H films. The results obtained from the present study demonstrated that hydrogen flow rate is an important deposition parameter in PECVD to synthesize nc-Si:H films.

Objective: Phosphorus doped hydrogenated nano-crystalline silicon (nc-Si:H) thin films were synthesized by catalytic chemical vapor deposition (Cat-CVD) method. Methods: The effect of deposition pressure on opto-electronic and structural properties was studied using various analysis techniques such as low angle XRD analysis, FTIR spectroscopy, Raman spectroscopy, UV-Visible spectroscopy, dark conductivity, etc. Results: From low angle XRD and Raman spectroscopy analysis, it is observed that an increase in deposition pressure causes Si:H films to transform and transit from amorphous to the crystalline phase. At optimized deposition pressure (300 mTorr), phosphorous doped nc- Si:H films having a crystallite size of ∼29 nm and crystalline volume fraction of ∼58% along with high deposition rate (∼29.7 Å/s) have been obtained. The band gap was found to be ∼1.98 eV and hydrogen content was as low as (∼1.72 at. %) for these films. Conclusion: The deposited films can be useful as an n-type layer for Si:H based p-i-n, tandem and c-Si hetero-junction solar cells.

Bismuth halide perovskites have been proposed as a non-toxic and chemically stable alternative to lead halide perovskites. Despite being highly stable, the devices based on bismuth perovskites have not been able to compete with the lead counterparts in terms of its efficiencies. The compounds that have been extensively studied i.e. Cs3Bi2I9 and MA3Bi2I9 form 0D (dimer) structures that possess wide indirect band gaps and poor charge transport properties which hinders the performance of devices based on these materials. Theoretical studies have revealed that replacing bigger A cation like Cs/MA by smaller cation like potassium (K) could favor the formation of layered 2D structures rather than 0D structure. We have synthesized inorganic K3Bi2I9 perovskite thin films by facile one-step spin coating method and investigated its structural, optical and morphological properties. The fabricated films showed strong absorption in UV and visible region of solar spectrum and possess optical band gap ∼2 eV. On comparison with the Cs analogue, it is observed that reduction in the cation size (Cs to K) hardly changes the band gap of K3Bi2I9 films which implies that the band gap of A3Bi2I9 perovskite is insensitive to A-site variation. Films deposited on preheated substrates showed comparatively good coverage without voids on the film surface. Our preliminary studies on this material showed that the films deposited by one-step solution method favored 0D structure rather than the expected 2D layered structure.

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.

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.

Tin doped indium oxide (ITO) films with high conductivity and charge carrier mobility were deposited at room temperature using RF-magnetron sputtering, without any post annealing treatment. It is observed that structural, optical, morphological and electrical properties of these ITO films depend on deposition time. All the synthesized films show optical transmittance > 90% and band gap of ∼ 3.6 eV. A change in crystal orientation from (222) to (400) with slight shift of peaks toward lower 2θ has been observed with the increase in deposition time. The synthesized films are compact, uniform and free from cracks. Moreover, there was an increase in grain size and shape with the progress in deposition time. Synthesized ITO films with (400) orientation have high conductivity (∼ 2 × 103 Ω−1 cm−1), high charge carrier mobility (∼ 348 cm2 V−1 s−1) and a high figure of merit (104 × 10−3 Ω−1). The synthesized thin films can have prospective applications in opto-electronic devices such as solar cells, light emitting diodes, etc.

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.

Hybrid lead halide perovskites have emerged as an attractive photoactive semiconductor for optoelectronic applications such as photovoltaics. However, their toxicity and stability issues pose significant challenges to its wide-scale applications and hence the need to find alternative perovskites that are stable and environmentally benign. Recently, double perovskites have been suggested as a potential alternative owing to their non-toxicity and high stability. In the present study, we report the first synthesis of Rb2AgBiI6 thin films in a cubic crystal structure using a facile room-temperature single-step solution process synthesis method and explore their potential optoelectronic applications. The structural, thermal, and mechanical stability, electronic, and optical properties are studied using various experimental techniques, and the results are further corroborated by first-principles density functional theory (DFT) calculations. The Rb2AgBiI6 film has an estimated band gap ∼ of 1.98 eV with the demonstrated thermal stability of ∼ 440 oC, suggesting its potential suitability for low-cost thin-film solar cells. The initial fabricated photovoltaic device without optimization of the synthesis conditions and device architecture show power conversion efficiency (PCE) of 0.1 % and an open-circuit voltage (Voc) of 0.46 V. The successful incorporation of Rb in Bi-based double perovskite should open the way to a new class of Rubidium-based perovskites with significant potential for optoelectronic applications.

In present work we report synthesis of rutile-TiO2 by using a simple solvothermal method. The formation of pure single phase rutile-TiO2 has been confirmed by X-ray diffraction (XRD) and Raman spectroscopy analysis. The XRD analysis revealed that as-prepared and soaked-TiO2 has pure rutile phase with tetragonal crystal structure. The field emission scanning electron microscopy and high resolution transmission electron microscopy analysis shows that as-prepared TiO2 has nano-rods like morphology whereas soaked-TiO2 has nano-flowers like morphology with atomically sharp edges. The UV–Visible spectroscopy analysis showed that as-prepared and soaked rutile-TiO2 nano-structures have absorption edge in the visible range and having band gap of ~ 3.58 eV. The field emission (FE) properties of as-prepared and soaked rutile-TiO2 nano-structures were investigated and it was observed that as-prepared and soaked rutile-TiO2 display excellent FE properties with low turn-on field (~ 4.8 V/µm for 10 µA/cm2), maximum current density [~ 444 µA/cm2 (as-prepared) and 508 µA/cm2 (soaked)] and superior current stability (~ 3 h for ~ 1 µA). The obtained results show that the rutile-TiO2 nanostructures can be useful for practical applications in vacuum nano/microelectronic devices.

In the present study we report the one step facile synthesis of pristine lead bismuth selenide (PbBi2Se4) and reduced graphene oxide (rGO) and its composites with PbBi2Se4. Formation of pristine PbBi2Se4 and rGO–PbBi2Se4 composite were confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. The surface morphology and topography investigated by using scanning electron microscopy and transmission electron microscopy revealed the formation of nano-flowers pristine PbBi2Se4. After coupling pristine PbBi2Se4 with rGO the surface morphology shows the formation of sharp vertically protruded nano-sheets/nano-flaks originated from the nano-flowers. Finally, the field emission properties of pristine PbBi2Se4 and rGO–PbBi2Se4 composite have been investigated. It has been observed that the rGO–PbBi2Se4 composite emitter exhibited excellent field emission properties with low turn-on field (~ 2.8 V/µm for 10 µA/cm2), high emission current density (~ 1288 µA/cm2 at 3.9 V/µm) and superior current stability (~ 4.5 h for ~ 1 µA) compare to pristine PbBi2Se4 emitter. Thus, the facile one step synthesis approach and robust nature of rGO–PbBi2Se4 composite emitter can provide prospects for the future development of large-area emitter applications such as flat-panel-display and vacuum micro/nanoelectronics devices.

The recent development of halide double perovskites A

In this paper, we synthesized lead-free cesium bismuth iodide (Cs3Bi2I9) perovskite films by solution process using one-step spin-coating technique. Formation of Cs3Bi2I9 perovskite was confirmed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy analysis. The XRD analysis showed that all Cs3Bi2I9 perovskite films were polycrystalline in nature, with hexagonal crystal structure and preferred-orientation along (006) direction. The environmental stability of Cs3Bi2I9 perovskite was confirmed by XRD analysis and UV–visible spectroscopy. Multiple XRD and UV–Vis spectra taken after long time spans revealed the stable nature of Cs3Bi2I9 perovskite films. The UV–visible spectroscopy and photoluminescence analysis showed that the perovskite films absorbed strongly in the visible region and had an optical band gap of ~2.1 eV. Surface morphology of Cs3Bi2I9 perovskite over the entire substrate surface was investigated using scanning electron microscopy. Thermo-gravimetric analysis showed that Cs3Bi2I9 perovskite was thermally stable up to ∼ 420 °C. Finally, solar cells fabricated using Cs3Bi2I9 perovskite material showed maximum power conversion efficiency (PCE) of 0.17%, with short circuit current density of 1.43 mA/cm2, open circuit voltage of 0.37 V and fill factor of 32%. Applying compositional engineering and optimizing the device structure should further improve the PCE. These results are a significant step toward fabrication of Cs3Bi2I9 perovskite-based solar cells.

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 (φTC = 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.

In present work, Mo films were deposited on corning glass substrates using DC-Magnetron sputtering. Influence of DC sputtering power on electrical, structural, morphological, optical and topological properties has been investigated by using Hall effect, Х-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV-Visible spectroscopy, non-contact-atomic force microscopy (NC-AFM) etc. It is observed that electrical resistivity and adhesion of Mo thin film were strongly affected by DC power. The synthesized Mo films were of few micrometer thicknesses (~ 0.9-1.6 m) with deposition rate in the range of 32-57 nm/min. Cross-hatch cut and Scotch tape adhesion test showed that all Mo films have good adhesion to the substrate. XRD analysis showed that as-deposited Mo films have preferred orientation in (110) direction and with enhancement in its crystallinity and average grain size with an increase in the DC sputtering power. Furthermore, XRD analysis showed that the Mo films deposited at DC sputtering power 300 W exhibit tensile strain, while deposited at DC sputtering power 350 W – exhibit compressive strain. FE-SEM analysis showed that all Mo films are dense, homogeneous and free of flaws and cracks. In the visible range of the spectrum, an increase in an average reflection of Mo films with DC sputtering power was observed by UV-Visible spectroscopy analysis. NC-AFM characterization revealed that the surface roughness of the films increases with an increase in the DC sputtering power. Hall effect measurements showed that the electrical resistivity of Mo films decreases while charge carrier mobility show increasing trend with increase in DC sputtering power. The obtained results suggest that as-synthesized Mo thin films with DC power 300 W have potential application as a back contact material for chalcopyrite compounds based on solar cells due to good adhesion and low electrical resistivity. В даній роботі, плівки Mo осаджувалися на підкладках із скла з використанням магнетронного розпилення при постійному струмі. Досліджено вплив потужності розпилення на електричні, структурні, морфологічні, оптичні та топологічні властивості за допомогою ефекту Холла, рентгенівської дифракції, автоелектронної скануючої мікроскопії, спектроскопії в УФ та видимої областях, неконтактної атомно-силової мікроскопії, тощо. Виявлено, що потужність постійного струму суттєво впливає на електричний опір і адгезію тонкої плівки Мо. Синтезовані плівки Mo мали товщину декількох мікрометрів (~ 0.9-1.6 мкм) зі швидкістю осадження в діапазоні 32-57 нм/хв. Випробування показали, що всі плівки Mo мають гарну адгезію до підкладки. Рентгено-дифракційний аналіз показав, що свіжосконденсовані плівки Mo мають переважну орієнтацію (110) і поліпшення її кристалічності та середнього розміру зерна зі збільшенням потужності розпилення при постійному струмі. Крім того, рентгенодифракційний аналіз показав, що плівки Mo, нанесені при потужності розпилення  300 Вт, демонструють деформацію розтягування, в той час як нанесені при потужності розпилення  350 Вт демонструють деформацію стиску. Результати автоелектронної скануючої мікроскопії показали, що всі плівки Mo щільні, однорідні і вільні від дефектів і тріщин. При спектроскопічному аналізі спостерігалося збільшення середнього коефіцієнту відбиття плівок Mo з потужністю розпилення спостерігалося у видимому діапазоні спектра. Неконтактна атомно-силова мікроскопія показала, що шорсткість поверхні плівок збільшується зі збільшенням потужності розпилення при постійному струмі. Вимірювання ефекту Холла показало, що електричний опір плівок Mo зменшується, а рухливість носіїв заряду збільшується з ростом потужності розпилення при постійному струмі. Отримані результати свідчать про те, що синтезовані тонкі плівки Мо з потужністю постійного струму  300 Вт мають перспективу застосування як матеріалу зворотного контакту для сполук халькопіритів на основі сонячних елементів завдяки хорошій адгезії та низькому електричному опору.

In the present study, we report synthesis of tin sulfide (SnS) nano-rods using a simple solvothermal method at different reaction time period. The formation of single phase SnS has been confirmed by X-ray diffraction (XRD) and Raman analysis. The XRD analysis revealed that the predominant phase in all prepared samples is orthorhombic SnS. The formation of nano-rods of SnS was confirmed by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) analysis. To investigate the optical properties of SnS nano-rods UV–visible spectroscopy analysis was carried out. We observed that the band gap of SnS nano-rods decreases with increase in reaction time and can be attributed to the quantum confinement effect. Finally, field emission investigations on the SnS nano-rods at the base pressure of 1 × 10− 8 mbar were carried out and found to be superior to the other chalcogenide nanostructures. As-synthesized SnS nano-rods emitter exhibits excellent field emission properties such as low turn-on field (~ 2.5 V/µm for 10 µA/ cm2), high emission current density (~ 647 µA/cm2 at 3.9 V/µm) and superior current stability (~ 5 h for ~ 1 µA). Thus, the facile one-step synthesis approach and robust nature of SnS nano-rods emitter can provide prospects for the future development of large-area emitter applications such as flat-panel-display devices.

Single crystal thin films of CdS were grown onto glass substrates by RF magnetron sputtering at var ious substrate temperatures. Structural, optical and morphology properties of these films were investigated through low angle XRD, Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive x-ray (EDX) spectroscopy, UV-Visible spectroscopy etc. Formation of single crystal CdS films has been confirmed by low angle XRD and Raman spectroscopy analysis. Low angle XRD showed that CdS films has preferred orientation in (111) direction. Improvement of crystallinity and increase in average grain size of CdS crystallites has been observed with increase in substrate temperature. Surface morphology investigated using SEM showed that CdS films deposited over entire range of substrate temperature are highly smooth, dense, homogeneous, and free of flaws and cracks. The EDX data revealed the formation of high-quality nearly stoichiometric CdS films by RF magnetron sputtering. Furthermore, the CdS films deposited at low substrate temperatures (< 200 0C) are slightly S rich while deposited at higher substrate temperatures (> 200 0C) are slightly Cd rich. The UV-Visible spectroscopy analysis showed that an average transmission ~ 80-90 % in the visible range of the spectrum having band gap ~ 2.28 -2.38 eV, which is quite close to the optimum value of band gap for a buffer layer in CdTe/CdS, Cu2S/CdS hetero-junction solar cells.

The recent development of halide double perovskites A2B'B"X6 with favorable band gaps have provided a new search direction for stable Pb-free perovskite solar cells. Here, we propose a new lead free double perovskite Cs2TlBiI6 as a potential candidate for perovskite solar cell absorber. We probe the structural, electronic and optical properties of this material through density functional theory calculations. Our calculations on this material show that Cs2TlBiI6 adopt cubic double perovskite structure with space group Fm-3m. Using PBE exchange-correlation functional we obtain direct band gap of about 1.37 eV at the centre of Brillouin zone. The direct band gap and strong optical absorption of this material in the visible energy range of solar spectrum implies that Cs2TlBiI6 can be a potential candidate for perovskite based solar cell. Our fundamental calculations on this material would open up further possibility of experimental studies on TlBi based perovskite.

In present study nanocrystalline tungsten carbide (nc-WC) thin films were deposited by HW-CVD using heated W filament and CF4 gas. Influence of CF4 flow rate on structural, optical and electrical properties has been investigated. Formation of WC thin films was confirmed by low angle XRD, Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) analysis. Low angle XRD analysis revealed that WC crystallites have preferred orientation in (101) direction and with increase in CF4 flow rate the volume fraction of WC crystallites and its average grain size increases. Formation of nano-sized WC was also confirmed by transmission electron microscopy (TEM) analysis. UV-Visible spectroscopy analysis revealed increase in optical transmission with increase in CF4 flow rate. The WC film deposited for 40 sccm of CF4 flow rate show high transparency (- 80-85 %) ranging from visible to infrared wavelengths region. The band gap shows increasing trend with increase in CF4 flow rate (3.48-4.18 eV). The electrical conductivity measured using Hall Effect was found in the range - 103-141 S/cm over the entire range of CF4 flow rate studied. The obtained results suggest that these wide band gap and conducting nc-WC films can be used as low cost counter electrodes in DSSCs and co-catalyst in electrochemical water splitting for hydrogen production.