Search Results (34)

The vast majority of photocatalysts find it difficult to consistently and stably exhibit high performance due to the variability of sunlight intensity within a day, as well as the high energy consumption of artificial light sources. In this study, mechanoluminescent Sr₂MgSi₂O₇:Eu,Dy phosphors is combined with NiS@g-C₃N₄ composite to construct a ternary heterogeneous photocatalytic system, denoted as NCS. In addition to the enhanced separation efficiency of photogenerated charge carriers by the formation of a heterojunction, the introduction of Sr₂MgSi₂O₇:Eu,Dy provides an ultra-driving force for the photocatalytic reactions owing to its mechanoluminescence-induced excitation. Results show that the degradation rate of RhB increased significantly in comparison with pristine g-C₃N₄ and NiS@g-C₃N₄, indicating the obvious advantages of the ternary system for charge separation and migration. Moreover, the additional photocatalytic activity of NCS under ultrasound stimulation makes it a promising all-weather photocatalyst even in dark environments. This novel strategy opens up new horizons for the synergistic combination of light-driven and ultrasound-driven heterogeneous photocatalytic systems, and it also has important reference significance for the design and application of high-performance photocatalysts. Full article

This study proposed a novel perovskite/silicon heterojunction (SHJ) tandem device structure without an interlayer, represented as ITO/NiO/perovskite/SnO₂/MoO_X/i-a-Si:H/n-c-Si/i-a-Si:H/n-a-Si:H/Ag, which was investigated by Silvaco TCAD software. The recombination layer in this structure comprises the carrier transport layers of SnO₂ and MoO_X, where MoO_X serves dual functions, acting as the emitter for the SHJ bottom cell and as part of the recombination layer in the tandem cell. First, the effects of different recombination layers are analyzed, and the SnO₂/MoO_X layer demonstrates the best performance. Then, we systematically investigated the impact of the carrier concentration, interface defect density, thicknesses of the SnO₂/MoO_X layer, different hole transport layers (HTLs) for the top cell, absorption layer thicknesses, and perovskite defect density on device performance. The optimal carrier concentration in the recombination layer should exceed 5 × 10¹⁹ cm⁻³, the interface defect density should be below 1 × 10¹⁶ cm⁻², and the thicknesses of SnO₂/MoO_X should be kept at 20 nm/20 nm. CuSCN has been found to be the optimal HTL for the top cell. When the silicon absorption layer is 200 μm, the perovskite layer thickness is 470 nm, and the defect density of the perovskite layer is 10¹¹ cm⁻³, the planar structure can achieve the best performance of 32.56%. Finally, we studied the effect of surface texturing on the SHJ bottom cell, achieving a power conversion efficiency of 35.31% for the tandem cell. Our simulation results suggest that the simplified perovskite/SHJ tandem solar cell with a dual-functional MoO_X layer has the potential to provide a viable pathway for developing high-efficiency tandem devices. Full article

The development of reliable, highly sensitive hydrogen sensors is crucial for the safe implementation of hydrogen-based energy systems. This paper proposes a novel way to enhance the performance of hydrogen sensors through integrating Pd-SnO₂ nanofilms on the substrate with silicon nanowires (SiNWs). The samples were fabricated via a simple and cost-effective process, mainly consisting of metal-assisted chemical etching (MaCE) and electron beam evaporation. Structural and morphological characterizations were conducted using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The experimental results showed that, compared to those without SiNW structure or decorative Pd nanoparticles, the Pd-decorated SnO₂ nanofilm integrated on the SiNW substrates exhibited significantly improved hydrogen sensing performance, achieving a response time of 9 s at 300 °C to 1.5% H₂ and a detection limit of 1 ppm. The enhanced performance can be primarily attributed to the large surface area provided by SiNWs, the efficient hydrogen spillover effect facilitated by Pd nanoparticles, and the abundant oxygen vacancies present on the surface of the SnO₂ nanofilm, as well as the Schottky barrier formed at the heterojunction interface between Pd and SnO₂. This study demonstrates a promising approach for developing high-performance H₂ sensors characterized by ultrafast response times and ultralow detection limits. Full article

Tandem solar cells have the potential to be more efficient than the Shockley–Queisser limit imposed on single junction cells. In this study, optical and electrical modeling based on experimental data were used to investigate the possibility of boosting the performance of kesterite/c-Si tandem solar cells by inserting an alternative nontoxic TiO₂ buffer layer into the kesterite top subcell. First, with SCAPS-1D simulation, we determined the data reported for the best kesterite (CZTS (Eg = 1.5 eV)) device in the experiments to be used as a simulation baseline. After obtaining metric parameters close to those reported, the influence on the optoelectronic characteristics of replacing CdS with a TiO₂ buffer layer was studied and analyzed. Different top subcell absorbers (CZTS0.8Se0.2 (Eg = 1.4 eV), CZTS (Eg = 1.5 eV), CZTS (Eg = 1.6 eV), and CZT0.6Ge0.4S (Eg = 1.7 eV)) with different thicknesses were investigated under AM1.5 illumination. Then, to achieve current matching conditions, the c-Si bottom subcell, with an efficiency at the level of commercially available subcells (19%), was simulated using various top subcells transmitting light calculated using the transfer matrix method (TMM) for optical modeling. Adding TiO₂ significantly enhanced the electrical and optical performance of the kesterite top subcell due to the decrease in parasitic light absorption and heterojunction interface recombination. The best tandem device with a TiO₂ buffer layer for the top subcell with an optimum bandgap equal to 1.7 eV (CZT0.6Ge0.4S4) and a thickness of 0.8 µm achieved an efficiency of approximately 20%. These findings revealed that using a TiO₂ buffer layer is a promising way to improve the performance of kesterite/Si tandem solar cells in the future. However, important optical and electrical breakthroughs are needed to make kesterite materials viable for tandem applications. Full article

This study involved direct doping of In₂O₃ into silicon carbide (SiC) powder, resulting in 8.0 at% In-doped SiC powder. Subsequently, heating at 500 °C was performed to form a target, followed by the utilization of electron beam (e-beam) technology to deposit the In-doped SiC thin films with the thickness of approximately 189.8 nm. The first breakthrough of this research was the successful deposition of using e-beam technology. The second breakthrough involved utilizing various tools to analyze the physical and electrical properties of In-doped SiC thin films. Hall effect measurement was used to measure the resistivity, mobility, and carrier concentration and confirm its n-type semiconductor nature. The uniform dispersion of In ions in SiC was as confirmed by electron microscopy energy-dispersive spectroscopy and secondary ion mass spectrometry analyses. The Tauc Plot method was employed to determine the Eg values of pure SiC and In-doped SiC thin films. Semiconductor parameter analyzer was used to measure the conductivity and the I-V characteristics of devices in In-doped SiC thin films. Furthermore, the third finding demonstrated that In₂O₃-doped SiC thin films exhibited remarkable current density. X-ray photoelectron spectroscopy and Gaussian-resolved spectra further confirmed a significant relationship between conductivity and oxygen vacancy concentration. Lastly, depositing these In-doped SiC thin films onto p-type silicon substrates etched with buffered oxide etchant resulted in the formation of heterojunction p-n junction. This junction exhibited the rectifying characteristics of a diode, with sample current values in the vicinity of 10² mA, breakdown voltage at approximately −5.23 V, and open-circuit voltage around 1.56 V. This underscores the potential of In-doped SiC thin films for various semiconductor devices. Full article

A comparative analysis of three advanced architectures for tandem solar cells (SCs) is discussed, respectively: metal oxide, thin film, and perovskite. Plasmonic solar cells could further increase solar cell efficiency. Using this development, an innovative PV technology (an SHTSC based on metal oxides) represented by a four-terminal Cu₂O/c-Si tandem heterojunction solar cell is investigated. The experimental and numerical modelling study defines the main aim of this paper. The experimental approach to SHTSCs is analysed: (1) a Cu₂O layer is deposited using a magnetron sputtering system; (2) the morphological and optical characterization of Cu₂O thin films is studied. The electrical modelling of silicon heterojunction tandem solar cells (SHTSCs) is discussed based on five simulation tools for the optimized performance evaluation of solar devices. The main novelty of this paper is represented by the following results: (1) the analysis suggests that the incorporation of a buffer layer can improve the performance of a tandem heterojunction solar cell; (2) the effect of interface defects on the electrical characteristics of the AZO/Cu₂O heterojunction is discussed; (3) the stability of SHTSCs based on metal oxides is studied to highlight the degradation rate in order to define a reliable solar device. Perspectives on SHTSCs based on metal oxides, as well as Si perovskite tandem solar cells with metal oxides as carrier-selective contacts, are commented on. Full article

In this study, we present the fabrication and characterization of vertically oriented NiO/β polymorph n-Ga₂O₃/n+ Ga₂O₃ heterojunction rectifiers featuring a substantial area of 1 mm². A dual-layer SiN_X/SiO₂ dielectric field plate edge termination was employed to increase the breakdown voltage (V_B). These heterojunction rectifiers exhibit remarkable simultaneous achievement of high breakdown voltage and substantial conducting currents. In particular, the devices manifest V_B of 7 kV when employing a 15 µm thick drift layer doping concentration of 8.8 × 10¹⁵ cm⁻³, concurrently demonstrating a forward current of 5.5 A. The thick drift layer is crucial in obtaining high V_B since similar devices fabricated on 10 µm thick epilayers had breakdown voltages in the range of 3.6–4.0 kV. Reference devices fabricated on the 15 µm drift layers had V_B of 5 kV. The breakdown is still due to leakage current from tunneling and thermionic emission and not from avalanche breakdown. An evaluation of the power figure-of-merit, represented by V_B²/R_ON, reveals a value of 9.2 GW·cm⁻², where R_ON denotes the on-state resistance, measuring 5.4 mΩ·cm². The Coff was 4 nF/cm², leading to an R_ON × C_off of 34 ps and F_CO of 29 GHz. The turn-on voltage for these rectifiers was ~2 V. This exceptional performance surpasses the theoretical unipolar one-dimensional (1D) limit of both SiC and GaN, underscoring the potential of β-Ga₂O₃ for forthcoming generations of high-power rectification devices. Full article

In this report, the morphological, optical, electrical, and photovoltaic properties of copper oxide and calcium-doped copper oxide thin films produced via the spray coating method were studied. The thermal post treatment at 300 °C in an inert atmosphere allowed us to obtain a single phase of Cu₂O with 21 Ωcm of resistivity (ρ). In this study, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, and 10 wt% Ca admixtures with copper oxide were investigated. The determined optimal calcium dopant concentration was 4 wt%. XRD analysis was used to reveal the chemical composition of the produced layers. It was found that a calcium dopant does not change the layer composition but improves its electrical parameters. Based on UV-Vis spectra, the band gap energy and Urbach energy were calculated. The morphology of produced thin films was described as smooth and nanocrystalline, corresponding to a grain size calculated based on the Scherrer equation. Finally, it was shown that the developed protocol of low-resistivity copper oxide deposition via the spray coating technique can be successfully implemented in heterojunction solar cell production. The I–V parameters of Ag/n-type CzSi/REF:CuO_x and 4Ca:CuO_x/Carbon were collected, and the achieved efficiency was 2.38%. Full article

The optical and geometrical properties of transparent conductive oxide (TCO) are crucial factors influencing the efficiency of $\mathrm{a}-\mathrm{Si}:\mathrm{H}/\mathrm{c}-\mathrm{Si}$heterojunction (HIT) solar cells. Graphene is a potential candidate to be used as TCO due to its optical and electrical properties. Here, the effect of graphene as TCO is numerically analyzed by varying the number of graphene layers from one to ten. First, the optical properties are calculated based on the transmittance data, and then the HJT cell’s performance is simulated under the AM1.5 standard spectrum and the mean Atacama Desert solar spectral irradiance in Chile. In the modeling, the most relevant properties are calculated with the spectrum of the Atacama Desert. The most relevant values were obtained as follows: open circuit voltage $V_{oc}=721.4 \mathrm{mV}$, short circuit current $J_{sc}=39.6 \mathrm{mA}/{\mathrm{cm}}^2$, fill factor $FF=76.5\%$, and energy conversion efficiency $E_{ff}=21.6\%$. The maximum power of solar panels irradiated with the Atacama Desert spectrum exceeds the results obtained with the AM1.5 standard spectrum by $10\%$. When graphene is the transparent conducting oxide, quantum efficiency has a higher value in the ultraviolet range, which shows that it may be convenient to use graphene-based solar cells in places where ultraviolet intensity is high. Full article

Optimized vertical heterojunction rectifiers with a diameter of 100 µm, consisting of sputter-deposited p-type NiO forming a p–n junction with thick (10 µm) Ga₂O₃ drift layers grown by halide vapor phase epitaxy (HVPE) on (001) Sn-doped (10¹⁹ cm⁻³) β-Ga₂O₃ substrates, exhibited breakdown voltages >8 kV over large areas (>1 cm²). The key requirements were low drift layer doping concentrations (<10¹⁶ cm³), low power during the NiO deposition to avoid interfacial damage at the heterointerface and formation of a guard ring using extension of the NiO beyond the cathode metal contact. Breakdown still occurred at the contact periphery, suggesting that further optimization of the edge termination could produce even larger breakdown voltages. On-state resistances without substrate thinning were <10 mΩ.cm⁻², leading to power figure-of-merits >9 GW.cm⁻². The devices showed an almost temperature-independent breakdown to 600 K. These results show the remarkable potential of NiO/Ga₂O₃ rectifiers for performance beyond the limits of both SiC and GaN. The important points to achieve the excellent performance were: (1) low drift doping concentration, (2) low power during the NiO deposition and (3) formation of a guard ring. Full article

The comprehensive utilization of low-grade diatomite resources and the effective treatment of printing and dyeing wastewater have attracted widespread attention. The combined scrubbing-magnetic separation-acid leaching-roasting process was used to increase the SiO₂ content from 59.22% to 86.93%, reduce the Al₂O₃ content from 18.32% to 6.75%, and reduce the Fe₂O₃ content from 6.85% to 1.24% in the low-grade diatomite from Heilongjiang, China. The TiO₂/g-C₃N₄/diatomite nanocomposite was prepared by a facile ultrasonic-thermal polymerization method. In this ternary structure, diatomite skeleton effectively increased the surface area with abundant adsorption sites, prevented g-C₃N₄ from restacking, and facilitated the separation of electrons and holes via the formation of TiO₂/g-C₃N₄ heterojunctions. The degradation rate was 98.77%, 90.59%, and 89.16% for the three catalytic reaction cycles of the MB solution, respectively. The composite showed a high degradation rate of the MB solution after three cycles, which indicated that the composite had good recyclability. Through the free radical capture test, it was elucidated that O₂⁻·, h⁺, and ·OH all played a role in the photocatalytic reaction of the TiO₂/g-C₃N₄/diatomite to the MB solution, in which O₂⁻· was mainly responsible for the photocatalytic oxidation mechanism, and the reaction kinetics were further investigated. This nanostructured TiO₂/g-C₃N₄/diatomite composite has fascinating visible light catalytic activity and excellent stability. Full article

PV technology offers a sustainable solution to the increased energy demand especially based on mono- and polycrystalline silicon solar cells. The most recent years have allowed the successful development of perovskite and tandem heterojunction Si-based solar cells with energy conversion efficiency over 28%. The metal oxide heterojunction tandem solar cells have a great potential application in the future photovoltaic field. Cu₂O (band gap of 2.07 eV) and ZnO (band gap of 3.3 eV) are very good materials for solar cells and their features completely justify the high interest for the research of tandem heterojunction based on them. This review article analyzes high-efficiency silicon-based tandem heterojunction solar cells (HTSCs) with metal oxides. It is structured on six chapters dedicated to four main issues: (1) fabrication techniques and device architecture; (2) characterization of Cu₂O and ZnO layers; (3) numerical modelling of Cu₂O/ZnO HTSC; (4) stability and reliability approach. The device architecture establishes that the HTSC is constituted from two sub-cells: ZnO/Cu₂O and c-Si. The four terminal tandem solar cells contribute to the increased current density and conversion efficiency. Cu₂O and ZnO materials are defined as promising candidates for high-efficiency solar devices due to the morphological, structural, and optical characterization emphasized. Based on multiscale modelling of PV technology, the electrical and optical numerical modelling of the two sub-cells of HTSC are presented. At the same time, the thermal stability and reliability approach are essential and needed for an optimum operation of HTSC, concerning the cell lifetime and degradation degree. Further progress on flexible HTSC could determine that such advanced solar devices would become commercially sustainable in the near future. Full article

In this paper, we investigate the effects of aluminum oxide (Al₂O₃) antireflection coating (ARC) on silicon heterojunction (SHJ) solar cells. Comprehensive ARCs simulation with Al₂O₃/ITO/c-Si structure is carried out and the feasibility to improve the short circuit current density (J_SC) is demonstrated. Based on the simulation results, we apply Al₂O₃ ARC on SHJ solar cells, and the increasement in J_SC to 1.5 mA/cm² is observed with an Al₂O₃ layer thickness of 20 nm. It is because the total reflectance of SHJ solar cells is decreased by the shifting of the wavelength range on constructive and destructive light interference. As a result, we believe that the proposed Al₂O₃ ARC can support an effective engineering technic to increase J_SC and efficiency of SHJ solar cells. Full article

Silicon-based heterojunction (SHJ) solar cells demonstrate high efficiencies over their homojunction counterparts, revealing the potential of such technologies. We present here the first steps towards the development of molybdenum disulfide (MoS₂)/c-silicon heterojunction solar cells, consisting of a preliminary study of the MoS₂ material and numerical device simulations of MoS₂/Si heterojunction solar cells, using SILVACO ATLAS. Through the optical and structural characterization of MoS₂/SiO₂/Si samples, we found a significant sensitivity of the MoS₂ to ambient oxidation. Optical ellipsometry showed a bandgap of 1.87 eV for a 7 monolayer thick MoS₂ sample, suitable for the targeted application. Finally, we briefly introduce a device simulation and show that the MoS₂/Si heterojunction could lead to a gain in quantum efficiency, especially in the region with short wavelengths, compared with a standard a-Si/c-Si solar cell. Full article

In recent decades, dopant-free Si-based solar cells with a transition metal oxide layer have gained noticeable research interest as promising candidates for next-generation solar cells with both low manufacturing cost and high power conversion efficiency. Here, we report the effect of the substrate temperature for the deposition of vanadium oxide (V₂O_5−x, 0 ≤ X ≤ 5) thin films (TFs) for enhanced Si surface passivation. The effectiveness of SiO_x formation at the Si/V₂O_5−x interface for Si surface passivation was investigated by comparing the results of minority carrier lifetime measurements, X-ray photoelectron spectroscopy, and atomic force microscopy. We successfully demonstrated that the deposition temperature of V₂O_5−x has a decisive effect on the surface passivation performance. The results confirmed that the aspect ratio of the V₂O_5−x islands that are initially deposited is a crucial factor to facilitate the transport of oxygen atoms originating from the V₂O_5−x being deposited to the Si surface. In addition, the stoichiometry of V₂O_5−x TFs can be notably altered by substrate temperature during deposition. As a result, experimentation with the fabricated Si/V₂O_5−x heterojunction solar cells confirmed that the power conversion efficiency is the highest at a V₂O_5−x deposition temperature of 75 °C. Full article