High Band Gap Research Articles

Enhanced photoluminescence of a microporous quantum dot color conversion layer by inkjet printing

Owing to their high color purity, tunable bandgap, and high efficiency, quantum dots (QDs) have gained significant attention as color conversion materials for high-end display applications. Moreover, inkjet-printed QD pixels show great potential for realizing full-color mini/micro-light emitting diode (micro-LED)-based displays. As a color conversion layer, the photoluminescence intensity of QDs is limited by the insufficient absorptance of the excitation light due to the lack of scattering. Conventional scatterers, such as titanium dioxide microparticles, have been applied after additional surface engineering for sufficient dispersity to prevent nozzle clogging in inkjet printing process. In our work, as an alternative approach, we use inkjet printing for depositing a phase separating polymer ink based on polystyrene (PS) and polyethylene glycol (PEG). QD/polymer composite pixels with scattering micropores are realized. The morphology of the micropores can be tailored by the weight ratio between PS and PEG which enables the manipulation of scattering capability. With the presence of the microporous structure, the photoluminescence intensity of the QD film is enhanced by 110% in drop-cast films and by 35.3% in inkjet-printed QD pixel arrays compared to the reference samples.

Dipoles with donor-π-acceptor structure inhibit ion migration to improve the efficiency and stability of inverted perovskite solar cells

Organic-inorganic hybrid perovskites (PVK) have aroused big enthusiasm of many researchers due to their excellent photoelectric properties. However, PVK films always inevitability demonstrate large number of defects, thus greatly affect the performance and stability of the device. Many parts of the defects are aroused from ion migrations because of the weak antibonding between Pb and I. Here, we use 4-Amino-3,5-difluorobenzonitrile (AFBN) to regulate the light-absorbing layer of perovskite films. The AFBN molecules with donor-π-acceptor (D-π-A) structure can simultaneously interact with MA+/Pb2+ cations and I- anions in PVK, which can validly inhibit ion migration and effectively restrain non-radiative recombination, thus improves the photoelectric performance of inverted perovskite solar cells (i-PSCs). The AFBN-based device achieved a champion efficiency of 18.55%, which is a high PCE for inverted PSCs with simple structure of FTO/NiOx/perovskite/PCBM/BCP/Ag and for devices with relatively high band gap of 1.62 eV, while the control one only shows an efficiency of 16.37%. Meanwhile, the modified devices demonstrate excellent humidity stability. This work provides a new path for dipoles with donor-π-acceptor structure to inhibit ion migrations for improved efficiency and stability of reverse PSCs.

Extraordinary Polarization and Thickness Dependences of Photocarrier Dynamics in PdSe2 Ribbons.

Pentagonal palladium diselenide (PdSe2) stands out for its exceptional optoelectronic properties, including high carrier mobility, tunable bandgap, and anisotropic electronic and optical responses. Herein, we systematically investigate photocarrier dynamics in PdSe2 ribbons using polarization-resolved optical pump-probe spectroscopy. In thin PdSe2 ribbons with a semiconductor phase, the photocarrier dynamics are found to be dominated by intraband hot-carrier cooling, interband recombination, and the exciton effect, showing weak crystalline orientation dependences. Conversely, in thick semimetal-phase PdSe2 ribbons, the photocarrier relaxations governed by the electron-optical/acoustic phonon scattering strongly depend on the sample orientation, albeit with a degradation in in-plane anisotropy following hot-carrier cooling. Furthermore, we analyze the correlations between photocarrier dynamics and anisotropic energy dispersions of electronic structures across a wide range in k space, as well as the contributions from the anisotropic electron-phonon couplings. Our study provides crucial insights for developing polarization-sensitive photoelectronic devices based on PdSe2.

SnS2 with different exposed crystal planes for NO2 gas sensing

Tin disulfide (SnS2), is an emerging two-dimensional metal sulfide material with high electronegativity and suitable bandgap, making it a promising candidate for NO2 sensors. In this study, SnS2 thin sections with different exposed crystal planes were prepared from two different sulfur sources, and the effects of crystal sections on the growth of SnS2 and its NO2 sensing performance were studied. SnS2 micro sheets with (101) exposed crystal plane (SnS2-M) showed a smaller specific surface area than SnS2 nano sheets with (100) exposed crystal plane (SnS2-N). However, the crystal structure grown along the (101) plane direction provides a more favorable pathway for NO2 molecules, enhancing gas molecule adsorption and desorption, and exhibiting excellent performance in terms of sensitivity, repeatability, and response time. The gas sensing performance is not only influenced by the specific surface area but also significantly differs due to the exposure of different crystal planes. This result provides a certain reference value for the preparation of SnS2 with different crystal plane orientations for enhanced NO2 sensing.

Trimetallic nanocomposite as efficient nanosensors for the electrochemical detection of riboflavin

A composite is a material in which more than one metal salt or polymer can be mixed to enhance the processed product's physical and chemical properties. Due to their high band gap and enhanced excitation energy, composites can be used in numerous areas, such as solar cells, fuel cells, catalysts, and energy storage. Over a large area of applications in different fields, few studies have examined the ability of composites to sense the efficiency of riboflavin/vitamin B2. The present work explores the utilisation of trimetallic-based nanocomposite nanoparticles (TMNCsNPs) as a sensing material, which is synthesised and characterised in detail. The TMNCsNPs were used to understand the exposure of riboflavin to glassy carbon electrodes (GCE). Several electrochemical parameters were selected for the electrochemical study of the processed sensor. Initially, a long-range concentration of riboflavin (0.976–125 μM in PBS) was selected to check the efficiency of the produced sensor (TMNCsNPs/GCE). Low-to high-potential windows (0.5–15 mV/s) were chosen to measure the effect on TMNCsNPs/GCE in PBS. The chronoamperometry (CA) responses were analysed at different time intervals (0–900s). The cyclic response (CR) was analysed for TMNCsNPs/GCE sensor for up to one month. The interference of metal was examined, and real sample analysis was also conducted and discussed with possible mechanism.

Synthesis and Characterization of BaZrS3 Thin Films via Stacked Layer Methodology: A Comparative Study of BaZrS3 on Zirconium Foil and Silicon Carbide Substrates

Chalcogenide perovskites are an emerging class of semiconductors particularly interesting for optoelectronic applications due to their high absorption coefficients and direct bandgaps of 1.7–1.9 eV. However, few processing routes have been developed for the synthesis of BaZrS3 thin films. The advances in the fabrication of BaZrS3 thin films using zirconium foil as precursor and substrate is a new strategy, which is compared with the results of BaZrS3 thin films deposited on silicon carbide (SiC) substrate. In this study, a stacked layer methodology, inspired by the fabrication methods used for chalcopyrites and kesterites, is employed. The main objective is to facilitate the conversion of these layers into the desired perovskite structure through annealing. In methodology, we initiated the process by depositing elemental Zr by sputtering on SiC, followed by BaS on top of the Zr through electron beam evaporation and then sulphurized and annealed at high temperature (≈1000–1050 °C) to form BaZrS3 in an inductively heated physical vapour transport setup in the presence of elemental sulphur. In the parallel approach the methodology remains same, with the sole deviation of zirconium foil, which act as both the substrate and the source. The successful synthesis of BaZrS3 is confirmed by X‐Ray diffraction (XRD), scanning electron microscopy (SEM), and energy‐dispersive X‐Ray spectroscopy (EDS), while the optical band gap is analyzed by UV‐Vis. The microstructure of the BaZrS3 films shows the polycrystalline structure and surface roughness.

Fabricating S-scheme Sb2S3@CdSexS1–x quasi-one-dimensional heterojunction photoanodes by in-situ growth strategy towards photoelectrochemical water splitting

Nowadays, energy and environmental problems are becoming increasingly prominent in society, the development of clean and environmentally friendly energy is in line with the construction of ecological civilization and energy, which have attracted the attention of many researchers over the past decades. Narrow band gap semiconductor Sb2S3 is widely used in the area of solar cells because of its high light absorption coefficient and suitable bandgap width. However, numerous deep-level defects provide plentiful photogenerated carrier recombination sites, which restricts the improvement of photoelectrochemical properties seriously. In this work, S-scheme Sb2S3@CdSexS1–x core-shell quasi-one-dimensional heterojunction photoanodes were prepared on the FTO substrate by a two-step vapor transport deposition (VTD) method, chemical bath deposition (CBD) and in-situ selenization method. The results showed that CdSexS1–x nanoparticles (NPs) were tightly coated on the Sb2S3 nanorods (NRs). The photocurrent density of the Sb2S3@CdSexS1–x photoanodes was 1.61 mA cm–2 under 1.23 VRHE. Compared with the Sb2S3 photoanodes (0.61 mA cm–2), Sb2S3@CdSexS1–x photoanodes obtained a 2.64-fold improvement, and the dark current was effectively reduced. It showed excellent stability and fast photocurrent response in a 600 s optical stability test. It was concluded that: (1) The charge transfer mechanism of the S-scheme can avoid the problem of high recombination rate of photogenerated charge carriers due to the defects of Sb2S3 effectively, and realized spatial separation of photogenerated carriers. (2) The [hk1] oriented Sb2S3 NRs and the formed quasi-one-dimensional heterostructures promote efficient carrier transport. (3) The introduction of Se effectively regulated the band structure of CdS, slowed down the photocorrosion of S, and improved the stability of the photoelectrodes significantly.

Hydrogen-included plasma-assisted reactive sputtering for conductivity control of ultra-wide bandgap amorphous gallium oxide

Conductivity control of a-Ga2Ox films by cation/anion off-stoichiometry such as oxygen vacancy formation and hydrogen doping have been achieved by hydrogen-included plasma-assisted reactive sputter deposition system and physical and electrical properties of a-Ga2Ox films formed by this system have been investigated. The change in resistivity of a-Ga2Ox thin films deposited by the hydrogen-included plasma-assisted reactive sputtering was then investigated by changing the H2 flow rate ratio H2/(Ar + H2). The a-Ga2Ox thin films with semiconducting properties with a resistivity as low as 102 Ωcm was demonstrated using the plasma-assisted reactive sputtering system with addition to H2. Along with the low resistivity, the a-GaOx thin films with high film density and band gap energy of 5.2 g cm−3 and 4.8 eV were realized. The electrical resistivity of the a-Ga2Ox thin films can be controlled from 102 Ωcm to 105 Ωcm by appropriately controlling the amount of hydrogen introduced from the plasma. The results indicate that the hydrogen acts as a shallow donor, which increases the carrier concentration, can be efficiently introduced by using the plasma-assisted reactive sputtering system with addition to H2.

Thermoelectric properties of lead-free anti-perovskites X3BN (B = Bi, Sb, X = Mg, Ca, Sr): A theoretical study based on first-principles calculations and machine learning interatomic potential

The search for non-toxic and low-cost perovskites with high thermoelectric performance is still a challenge despite low thermal conductivity. The thermoelectric properties of nitride anti-perovskites X3BN (B = Bi, Sb, X = Mg, Ca, Sr) with a cubic structure were investigated using density functional theory and machine learning interatomic potential. The low Debye temperature and thermal conductivity were obtained due to strong lattice anharmonicity, and the phonon vibration modes were also analyzed. The high band degeneracy and suitable bandgap lead to a large power factor. The maximum power factor is 7.54 mW/mk2 for Mg3BiN at 900 K. We obtained a maximum ZT of 1.49 for p-type Sr3BiN, and it is 1.22 for n-type doping at 900 K. The ZT for Mg3BiN is 1.18 and 1.19 for p-type and n-type doping, respectively. Our calculations reveal that these anti-perovskites are excellent materials for non-toxic and low-cost thermoelectric applications.

Comprehensive performance analysis of perovskite solar cells based on different crystalline structures of MAPbI3

Perovskite solar cells (PSCs) have shown high optical absorption and consequently provide high conversion efficiency with stable performance. In our work, CH3NH3PbI3 (MAPbI3) as an absorber layer is analyzed for different crystalline structures. Cubic, tetragonal, and orthorhombic phases of perovskite material are investigated to check the impact of the crystalline structure on the solar cell performance. Both density of states and band structure are studied using Quantum-ESPRESSO package depending on density functional theory. Then, all relevant parameters were employed in SCAPS software and comprehensive study was done for examining the effect of the crystalline structure of perovskite layer on the solar cell performance. In-depth, analyses were conducted to evaluate key parameters, including open circuit voltage (Voc), short circuit current (Isc), fill factor (FF), and power conversion efficiency (PCE) considering the variations of perovskite layer thickness and bulk defect densities. The obtained results indicate that cells with cubic MAPbI3, which shows a notably higher bandgap of 1.7 eV and an enhanced optical absorption coefficient, especially in the higher wavelength range (around 105 cm−1), show better performance for almost all three scenarios. Cubic MAPbI3 cells achieve relatively higher peak efficiency of 26% when the absorber layer thickness is almost 900 nm. The investigation into absorber bulk defect densities reveals the critical role of defect levels in PSC performance. Adjusting defect levels from 1014 cm−3 to 1018 cm−3 results in deteriorating trends in Voc, Jsc, FF, and PCE. Jsc remains stable until a defect level of 1017 cm−3, highlighting a threshold where defects begin to impact charge carrier generation and separation. Doping effect has been studied, PCE remains stable until a critical doping level of 1016 cm−3 after which it drops significantly which indicates that doping is cautioned against due to its adverse effects on material and carrier transport. This finding holds significant promise for experimental solar cell fabrication, as it suggests that cubic MAPbI3’s superior bandgap and enhanced optical absorption could lead to more efficient and robust photovoltaic devices in real-world applications.

Enhancing the properties of Cd-free MgZnS buffer for solar cells by co-sputtering ZnS and Mg targets

The buffer is an essential component that connects the window and absorber layers in thin film solar cells, which has significant impacts on the performance of cell device. CdS is widely used buffer material, but it has drawbacks of toxicity and narrow band gap of 2.4 eV. This work explores the fabrication of a novel Cd-free MgZnS buffer layer through co-sputtering ZnS and Mg targets. The grain size, morphology, phase composition, transmittance and band gap of MgZnS films are manipulated by adjusting the substrate temperature, sputtering power of ZnS target and sputtering current of Mg target. The MgZnS film exhibits remarkable characteristics, including high crystallinity with grain size of about 35 nm, high transmittance of over 80%, and high band gap of 3.44 eV. The process parameters with favorable outcomes include substrate temperature of 300 °C, ZnS sputtering power of 100 W, and Mg sputtering current of 0.05 A. Furthermore, compared with the CdS buffer, the MgZnS buffer has better compactness and transmittance. This method provides a promising new and effective avenue to fabricate Cd-free buffers for solar cells.

Advancing bandgap tuning: Novel nitrogen doping in KLaTiO4 with uncompromised crystallinity

KLaTiO4 is a promising photocatalyst, producing 9.54(11) µmol of hydrogen gas per hour. Its high bandgap, of 4.09 eV, makes it unsuitable for direct photocatalysis under sunlight irradiation. In this study two novel methods of doping KLaTiO4 with nitrogen were studied, in an attempt to reduce the bandgap of KLaTiO4 without inducing structural degradation of the photocatalyst, which adversely affects the hydrogen evolution rate. The first method involves post-synthesis calcination of KLaTiO4 with urea under a nitrogen atmosphere, and the second method attempts to introduce nitrogen during synthesis, by replacing TiO2 with TiN as a starting reagent. The samples were structurally characterised using powder X-ray diffraction and their bandgap and photocatalytic performance determined by Tauc plot and hydrogen evolution testing. Density Function Theory calculations have been used to probe the likely site of nitrogen doping.

Effect of in contents on the electronic and optical properties of 2D GaN/InxGa1-xN heterostructures

Two-dimensional gallium nitride (2D GaN) has recently received considerable attention due to its excellent physical properties, including high stability, wide and tunable bandgap, and magnetism. 2D GaN offers an accessible way to apply in photocatalytic hydrogen production as composing to vdW heterostructures. Here, we report a first principles study based on the HSE06 functional for the 2D van der Waals (vdW) GaN/InxGa1-xN heterostructures with a tunable bandgap achieved through modulation of indium (In) contents. Such heterostructure is a bilayer vertically stacked by a monolayer of GaN and a monolayer of InxGa1-xN, both of which are graphite-like structures. In particular, the heterostructure bandgap decreases from 3.37 eV to 2.23 eV as In content increases from 0 to 0.5, accompanying by a significant transition from indirect to direct band gap. All of the studied heterostructures have suitable band edge positions for the redox potential of water decomposition at pH 0. Furthermore, increasing In content improves the visible light absorption, carrier mobility and establishes a more effective built-in electric field in the heterostructures. Our results prove that 2D GaN/InxGa1-xN heterostructure is highly suitable as a catalyst for photocatalytic water splitting and provides theoretical guidance for applying 2D GaN in photocatalytic hydrogen production.

Optoelectronic and Dielectric Properties of Tenorite CuO Thin Films Sprayed at Various Molar Concentrations

The work in hand presents the elaboration of CuO thin films using a home-made spray pyrolysis technique at room atmosphere. The films were synthesized on preheated glass substrate at 450 °C. The source solution molarity was varied from 0.025 to 0.1 mol/L. The films were characterized by employing X-Ray Diffraction technique, UV-Vis-NIR spectrophotometry, Scanning Electron Microscope imagery, Energy Dispersive Spectroscopy, and four-points probe techniques. The X-ray diffraction analysis confirmed that all films are polycrystalline with a preferred orientation along the plane (−111) of the monoclinic crystal structure phase of tenorite (CuO). The SEM images showed a homogeneous and smooth surface. Crystallinity and grain size were improved. The rise of solution concentration induced a reduction of transmittance and reflectance in the visible region. The energy gap, the absorption coefficient, the extinction coefficient, refractive index, dielectric constant (ԑr and ԑi) and loss energy were estimated from transmittance and reflectance data. The gap energy decreases from 2.72 to 2.56 eV. The film deposited for 0.025 mol/L exhibits the highest real part of the dielectric constant (ԑr ~ 17). The film resistivity which is in order of 102 Ω cm decreases with the increase of molar concentration. The estimated dielectric constant indicated that the resulting CuO thin films could be used as dielectric layers for optoelectronic devices working in Vis-NIR region of radiation. Furthermore, the relatively high band gap, high absorption coefficient and high conductivity of the film obtained at 0.075 mol/L, make them good candidates as absorption layers in solar cells applications.

Interfacial charge associated reliability improvement in arsenide/antimonide tunneling interfaced-junctionless TFET

This article focuses on the investigation of reliability improvement in the arsenide/antimonide tunable bandgap tunneling interfaced junctionless TFET (HD-HJLTFET) by introducing positive (donor) and negative (acceptor) localized interfacial trap charges (ITCs) at the semiconductor/oxide (S/O) and semiconductor/semiconductor (S/S) interface. The compound semiconducting materials, InAs (lower bandgap) and AlGaSb (higher bandgap) have been incorporated in the source and channel regions in the proposed device (HJLTFET). Further, to improve the device reliability against ITCs, a hetero dielectric engineered gated device has also been designed and analysed (HD-HJLTFET). In HD-HJLTFET, a high-k dielectric near source to channel (S/C) interface and low-k dielectric region towards drain to channel (D/C) interface has been used. It has been obtained that HD engineering enhances the microwave and harmonic distortion performance of HD-HJLTFET. It has been evaluated that HD-HJLTFET/ HJLTFET delivers ON current of 38.3 μA/14μA, transconductance 108 μS/23.2μS, cut-off frequency 805.8GHz/406.7GHz and gain of 223.5/197.4. Further results show that HD delivers gm2 (∼28% ↓), gm3 (∼9 times), second-order and third-order harmonic distortion (∼42% ↓ and ∼90% ↓), and total harmonic distortion (∼26% ↓) as compared to HJLTFET. The linearity parameters of HD-HJLTFET (VIP2, VIP3, IIP3, 1dB compression point, and IMD3) also showed marked improvement with negligible variation against different ITC polarity than its counter device, making it more reliable for low power microwave and distortion-free wireless communication systems.

Dual interface strategies enable efficient wide bandgap perovskite solar cells

High performance wide bandgap perovskite solar cells (WB-PSCs) have found widespread applications in tandem solar cells. In WB-PSCs, achieving a high conversion efficiency relies on the effective utilization of light absorption and minimization of electronic defects. In this work, electronic defects at the surface and grain boundaries of perovskite materials have been passivated by n-butylammonium bromide (BABr) to suppress carrier non-radiative recombination. Confirmed through x-ray powder diffraction and x-ray photoelectron spectroscopy spectra, ultra-thin two-dimensional (2D) perovskite layers were successfully generated on a perovskite surface. The BABr-treated devices exhibited an increased fill factor and open circuit voltage (VOC) compared to the references. Furthermore, a nanotextured electrode with a roughness of 22.98 nm was employed to trap light. The nanotextured buried interface not only promoted light utilization but also alleviated residual stress and micro-strain in the perovskite film compared to the smooth substrate. Finally, the champion WB-PSC achieved a power conversion efficiency of 20.46% in the reverse scan. These findings pave a promising path for the development of solution-processed perovskite films on nanotextured silicon substrates to improve the performance of monolithic tandem solar cells.

A new superior electronic properties Si allotrope for power electronic device applications

A new I−4 space group silicon allotrope is proposed in this paper. The electronics properties, mechanical properties and Ag(100)/I4Si(100) interface properties are studied using first principle calculations method. The results of the phonon show that I−4 Si is dynamically stable. Elastic constants reveal I−4 Si is dynamical stable. Electronics properties calculations reveal that the CBM and VBM of I−4 Si are at X and M point, which indicates that I−4 Si is an indirect band gap semiconductor with a high band gap of 1.95 eV. To satisfy the demands for fabricating electronic devices, the N-type doping, P-type doping and Ohmic contact are studied, too. The fermi energy level of N-type and P-type I−4 Si move into conduction band and valence band, respectively. The Schottky barrier of Ag/I-4 interface is 0.65 eV. Meanwhile, the current-voltage curve becomes highly symmetric, suggesting an Ohmic behavior of the Ag(100)/I4Si(100) interface. Critical breakdown field calculations results show that the critical breakdown field of I−4 Si is 9.05 × 105 V cm−1, which is 3.02 times that of the diamond Si. Because band gap and critical breakdown field of I-4 Si are much greater than that of diamond Si, I-4 Si is potential electronic semiconductor material. Thus, I−4 Si can be applied in the field of modern power electronic device applications due to its superior electronic properties.

Effect of silver doping on the band gap tuning of tungsten oxide thin films for optoelectronic applications

In the cutting-edge world, semiconductor metal oxides usually tend to have a high optical band gap (>3.0 eV), significantly acceptable for potential optoelectronic applications. The present study discusses the synthesize of pristine tungsten trioxide (WO3) and Silver (Ag) doped WO3 (Ag: WO3) thin films onto a glass substrate at 450 °C, with varying concentrations of Ag doping (2, 4, 6, 8 and 10 at.%) using a simple Spray Pyrolysis Technique. Field emission scanning electron microscopy (FESEM) analysis showed the presence of particles in the WO3 and Ag: WO3 materials. The X-ray diffraction (XRD) pattern confirmed that the samples' hexagonal structure remained intact. In addition, Rietveld refinement was used for the samples to study the crystal structure meticulously. Because of the surface plasmon resonance effect, the samples' distinguishing characteristics were visible in their optical nature. For pristine WO3, the experimental band gap was determined to be 3.20 eV, and for varying doping concentrations, it was found to be 3.15 eV–2.90 eV, respectively. Furthermore, the fracture has remained imperceptible at elevated concentrations, resulting in a substantial influence on the optical characteristics of 10% Ag: WO3 thin films. The estimated redox potential for 2% Ag: WO3 shows a considerable influence of the band edge potential of the Conduction Band (CB) and Valance Band (VB). The activation energy was determined using temperature-dependent electrical resistivity and exhibited an ohmic nature. The synthesized material exhibited a negative temperature coefficient (NTC) effect at higher concentrations of doping, suggesting its potential applicability as a thermistor. A comprehensive analysis of this present study indicates that Ag can be a viable candidate for doping on WO3 thin films for use in optoelectronic devices.

A new path towards ultra-high efficient laser power converters: Silicon carbide-based multijunction devices

Current high power laser transmission technology faces two major limitations to improve the efficiency of the photovoltaic receivers: the intrinsic entropic losses associated to low bandgap materials (such as GaAs) and the series resistance losses that degrade the device performance at high power densities. The use of high bandgap materials and new architectures for laser power converters (LPC) have been pointed out as alternatives to overcome these limitations. In this work, three silicon carbide polytypes (3C, 4H and 6H) are proposed as base materials for the standard horizontal laser power converter (hLPC) architecture and the Vertical Epitaxial Hetero-Structure Architecture (VEHSA). 3C SiC based hLPCs outperform the power converters based on the other two polytypes, achieving a maximum efficiency of 84.6% at ▪, but suffer from series resistance losses, that deteriorate their efficiency, at higher laser power densities. This issue is solved with 3C SiC 4 cells VEHSAs that demonstrated increasing efficiency with the input power, reaching a maximum of 87.4% at ▪. The VEHSA reduced number of cells minimize the risks of efficiency losses due to current mismatch between cells. These results support the feasibility of a new generation of LPCs capable of efficiently convert ultra-high laser power densities.

H2 production based on a ternary mixture of commercial CuO-NiO-TiO2 in a solar pilot plant

Glycerol is a by-product in biodiesel production (in the range of g·L−1), so its photoreforming by photocatalysis is a way of valorising it. TiO2 in photocatalysis has been widely studied, although its efficiency is limited by the high energy band gap, and the electron-hole recombination. Its combination with different semiconductors should improve charge separation, extending also the absorption from UV to visible light. Cu and Ni oxides are two of the most efficient low-cost transition metal oxide catalysts. Experiments were carried out in a 25 L pilot plant connected to a compound parabolic solar collector. Different combinations of the three semiconductors, based on the concentration of each metal on TiO2 (Me, 5%, 7.2% and 10%) were evaluated. Evonik P25-TiO2, CuO and NiO were combined by mechanical mixing. Hydrogen was quantified by a micro gas chromatograph, and copper and nickel leaching by ICP-MS. The best hydrogen production (0.060 mMol kJ−1) was attained with a proportion of 10:1 of TiO2:MeO, that corresponds to a total metal concentration of 7.2 wt%, being Cu and Ni in the same proportion. Metal content in solution increased as the reaction progressed, but Ni lixiviation of <0.012 mg L−1 was not significant. Significant Cu leaching (>1 mg L−1) was observed. This article presents novel results, in a solar pilot plant, for determining which ternary mixture can give better results, as well as metal leaching into water. Handling relevant volume of water in anoxic conditions can help to understand the application of this technology for the production of hydrogen.