Search Results (14)

In the purpose of enhancing solar cell efficiency and sustainability, zinc selenide (ZnSe) and silicon (Si) play indispensable roles, offering a compelling combination of stability and transparency while also highlighting their abundant availability. This study utilizes the SCAPS_1D tool to explore diverse heterojunction setups, aiming to solve the nuanced correlation between key parameters and photovoltaic performance, therefore contributing significantly to the advancement of sustainable energy solutions. Exploring the performance analysis of heterojunction solar cell configurations employing ZnSe and Si elements, various configurations including SnO₂/ZnSe/p_Si/p⁺_Si, SnO₂/CdS/p_Si/p⁺_Si, TiO₂/ZnSe/p_Si/p⁺_Si, and TiO₂/CdS/p_Si/p⁺_Si are investigated, delving into parameters such as back surface field thickness (BSF), doping concentration, operating temperature, absorber layer properties, electron transport layer properties, interface defects, series and shunt resistance. Among these configurations, the SnO₂/ZnSe/p_Si/p⁺_Si configuration with a doping concentration of 10¹⁹ cm⁻³ and a BSF thickness of 2 μm, illustrates a remarkable conversion efficiency of 22.82%, a short circuit current density (J_sc) of 40.33 mA/cm², an open circuit voltage (V_oc) of 0.73 V, and a fill factor (FF) of 77.05%. Its environmentally friendly attributes position it as a promising contender for advanced photovoltaic applications. This work emphasizes the critical role of parameter optimization in propelling solar cell technologies toward heightened efficiency and sustainability. Full article

This study explores the enhancement of α-Fe₂O₃ (hematite) nanorod arrays for photoelec-trochemical applications by constructing a Cu₂ZnSnS₄ (CZTS) heterojunction. While α-Fe₂O₃ offers good stability, a low cost, and environmental benefits, its efficiency is limited by slow oxygen evolution kinetics, high carrier recombination rates, and low conductivity. By introducing CZTS, a material with strong light absorption and charge transport properties, we enhance the separation of photogenerated charge carriers, reduce charge transfer resistance, and increase the carrier concentration, thereby boosting the overall photoelectrochemical performance. The experimental results show that a modified FC-15 photoanode achieves a photocurrent density of 3.40 mA/cm² at 1.60 V vs. RHE, a substantial increase compared to 0.40 mA/cm² for unmodified α-Fe₂O₃. Band gap analysis reveals a reduced band gap in the FC-15 material, enhancing light absorption and boosting the photoelectrocatalytic performance. In photoelectrochemical water-splitting tests, the FC-15 photoanode achieves a hydrogen production rate of 41.6 μmol/cm²/h, which is significantly improved over the unmodified sample at 5.64 μmol/cm²/h. These findings indicate that the CZTS/α-Fe₂O₃ heterojunction effectively promotes charge separation, enhances charge transport, and improves light absorption, substantially increasing photocatalytic efficiency. This heterojunction approach offers new insights and technical strategies for developing photocatalytic materials with potential applications in renewable energy. Full article

The research referred to in this study examines the morphological, structural, and optical characteristics of kesterite (Cu_1−xAg_x)₂ZnSnS₄ (CAZTS) thin films, which are produced using a process known as thermal evaporation (TE). The study’s main goal was to determine how different Ag contents affect the characteristics of CAZTS systems. X-ray diffraction (XRD) and Raman spectroscopy were used to confirm the crystal structure of the CAZTS thin films. Using a mathematical model of spectroscopic ellipsometry, the refractive index (n) represented the real part of the complex thin films, the extinction coefficient (k) portrayed the imaginary part, and the energy bandgap of the fabricated thin films was calculated. The energy bandgap is a crucial parameter for solar cell applications, as it determines the wavelength of light that the material can absorb. The energy bandgap was found to decrease from 1.74 eV to 1.55 eV with the increasing Ag content. The ITO/n-CdS/p-CAZTS/Mo heterojunction was well constructed, and the primary photovoltaic characteristics of the n-CdS/p-CAZTS junctions were examined for use in solar cells. Different Ag contents of the CAZTS layers were used to determine the dark and illumination (current–voltage) characteristics of the heterojunctions. The study’s findings collectively point to CAZTS thin layers as potential absorber materials for solar cell applications. Full article

This work explores the effect of a Zn_1−xSn_xO_y (ZTO) layer as a potential replacement for CdS in Sb₂(S,Se)₃ devices. Through the use of Afors-het software v2.5, it was determined that the ZTO/Sb₂(S,Se)₃ interface exhibits a lower conduction band offset (CBO) value of 0.34 eV compared to the CdS/Sb₂(S,Se)₃ interface. Lower photo-generated carrier recombination can be obtained at the interface of the ZTO/Sb₂(S,Se)₃ heterojunction. In addition, the valence band offset (VBO) value at the ZTO/Sb₂(S,Se)₃ interface increases to 1.55 eV. The ZTO layer increases the efficiency of the device from 7.56% to 11.45%. To further investigate the beneficial effect of the ZTO layer on the efficiency of the device, this goal has been achieved by five methods: changing the S content of the absorber, changing the thickness of the absorber, changing the carrier concentration of ZTO, using various Sn/(Zn+Sn) ratios in ZTO, and altering the thickness of the ZTO layer. When the S content in Sb₂(S,Se)₃ is around 60% and the carrier concentration is about 10¹⁸ cm⁻³, the efficiency is optimal. The optimal thickness of the Sb₂(S,Se)₃ absorber layer is 260 nm. A ZTO/Sb₂(S,Se)₃ interface with a Sn/(Zn+Sn) ratio of 0.18 exhibits a better CBO value. It is also found that a ZTO thickness of 20 nm is needed for the best efficiency. Full article

This study details the rational design and synthesis of Cu₂ZnSnS₄ (CZTS)-doped anatase (A) heterostructures, utilizing earth-abundant elements to enhance the efficiency of solar-driven water splitting. A one-step hydrothermal method was employed to fabricate a series of CZTS–A heterojunctions. As the concentration of titanium dioxide (TiO₂) varied, the morphology of CZTS shifted from floral patterns to sheet-like structures. The resulting CZTS–A heterostructures underwent comprehensive characterization through photoelectrochemical response assessments, optical measurements, and electrochemical impedance spectroscopy analyses. Detailed photoelectrochemical (PEC) investigations demonstrated notable enhancements in photocurrent density and incident photon-to-electron conversion efficiency (IPCE). Compared to pure anatase electrodes, the optimized CZTS–A heterostructures exhibited a seven-fold increase in photocurrent density and reached a hydrogen production efficiency of 1.1%. Additionally, the maximum H₂ production rate from these heterostructures was 11-times greater than that of pure anatase and 250-times higher than the original CZTS after 2 h of irradiation. These results underscore the enhanced PEC performance of CZTS–A heterostructures, highlighting their potential as highly efficient materials for solar water splitting. Integrating Cu₂ZnSnS₄ nanoparticles (NPs) within TiO₂ (anatase) heterostructures implied new avenues for developing earth-abundant and cost-effective photocatalytic systems for renewable energy applications. Full article

This research successfully synthesized SnO₂@ZnIn₂S₄ composites for photocatalytic tap water splitting using a rapid two-step microwave-assisted synthesis method. This study investigated the impact of incorporating a fixed quantity of SnO₂ nanoparticles and combining them with various materials to form composites, aiming to enhance photocatalytic hydrogen production. Additionally, different weights of SnO₂ nanoparticles were added to the ZnIn₂S₄ reaction precursor to prepare SnO₂@ZnIn₂S₄ composites for photocatalytic hydrogen production. Notably, the photocatalytic efficiency of SnO₂@ZnIn₂S₄ composites is substantially higher than that of pure SnO₂ nanoparticles and ZnIn₂S₄ nanosheets: 17.9-fold and 6.3-fold, respectively. The enhancement is credited to the successful use of visible light and the facilitation of electron transfer across the heterojunction, leading to the efficient dissociation of electron–hole pairs. Additionally, evaluations of recyclability demonstrated the remarkable longevity of SnO₂@ZnIn₂S₄ composites, maintaining high levels of photocatalytic hydrogen production over eight cycles without significant efficiency loss, indicating their impressive durability. This investigation presents a promising strategy for crafting and producing environmentally sustainable SnO₂@ZnIn₂S₄ composites with prospective implementations in photocatalytic hydrogen generation. Full article

Building heterojunctions is a promising strategy for the achievement of highly efficient photocatalysis. Herein, a novel SnIn₄S₈@ZnO Z-scheme heterostructure with a tight contact interface was successfully constructed using a convenient two-step hydrothermal approach. The phase composition, morphology, specific surface area, as well as photophysical characteristics of SnIn₄S₈@ZnO were investigated through a series of characterization methods, respectively. Methylene blue (MB) was chosen as the target contaminant for photocatalytic degradation. In addition, the degradation process was fitted with pseudo-first-order kinetics. The as-prepared SnIn₄S₈@ZnO heterojunctions displayed excellent photocatalytic activities toward MB degradation. The optimized sample (ZS800), in which the molar ratio of ZnO to SnIn₄S₈ was 800, displayed the highest photodegradation efficiency toward MB (91%) after 20 min. Furthermore, the apparent rate constant of MB photodegradation using ZS800 (0.121 min⁻¹) was 2.2 times that using ZnO (0.054 min⁻¹). The improvement in photocatalytic activity could be ascribed to the efficient spatial separation of photoinduced charge carriers through a Z-scheme heterojunction with an intimate contact interface. The results in this paper bring a novel insight into constructing excellent ZnO-based photocatalytic systems for wastewater purification. Full article

This article describes the effective synthesis of colloidal SnO₂ quantum dots and ZnWO₄ nanorods using wet chemical synthesis and hydrothermal synthesis, respectively. The resulting ZnWO₄-SnO₂ core–shell nanorod heterostructure is then made, and its structural, optical, and morphological properties are assessed using XRD, SEM, TEM, and DRS. The heterojunction’s structural confinement increases the exposure of its reactive sites, and its electronic confinement promotes its redox activity. The heterostructure subsequently exhibits a smaller bandgap and better light-harvesting capabilities, resulting in increased photoelectrochemical performance. The heterostructure of core–shell nanorods shows promise for usage in a range of optoelectronic devices and effective solar energy conversion. Full article

This paper describes the simulation by Solar Cell Capacitance Simulator-1D (SCAPS-1D) software of ZnO/CdS/SnS/NiO/Au solar cells, in which zinc oxide (ZnO) is used as transparent conductive oxide (TCO) and nickel oxide (NiO) is used as a hole transport layer (HTL). The effects of absorber layer (SnS) thickness, carrier concentration, SnS defect density, NiO HTL, ZnO TCO, electron affinity and work function on cell performance have been evaluated. The effect of interface defect density of SnS/CdS on the performance of the heterojunction solar cell is also analysed. As the results indicate, a maximum power conversion efficiency of 26.92% was obtained. Full article

Direct Z-scheme photocatalysts have attracted extensive attention due to their strong redox ability and efficient separation of photogenerated electron-hole pairs. In this study, we constructed two types of ZnS/SnS₂ heterojunctions with different stacking models of ZnS and SnS₂ layers, and investigated their structures, stabilities, and electronic and optical properties. Both types of heterojunctions are stable and are direct Z-scheme photocatalysts with band gaps of 1.87 eV and 1.79 eV, respectively. Furthermore, their oxidation and reduction potentials straddle the redox potentials of water, which makes them suitable as photocatalysts for water splitting. The built-in electric field at the heterojunction interface improves the separation of photogenerated electron-hole pairs, thus enhancing their photocatalytic efficiency. In addition, ZnS/SnS₂ heterojunctions have higher carrier mobilities and light absorption intensities than ZnS and SnS₂ monolayers. Therefore, the ZnS/SnS₂ heterojunction has a broad application prospect as a direct Z-scheme visible-light-driven photocatalyst for overall water splitting. Full article

Organic–inorganic ternary nanohybrids consisting of oxidized-single walled carbon nanohorns-SnO₂-polyvinylpyrrolidone (ox-SWCNH/SnO₂/PVP) with stoichiometry 1/1/1 and 2/1/1 and ox-SWCNH/ZnO/PVP = 5/2/1 and 5/3/2 (all mass ratios) were synthesized and characterized as sensing films of chemiresistive test structures for ethanol vapor detection in dry air, in the range from 0 up to 50 mg/L. All the sensing films had an ox-SWCNH concentration in the range of 33.3–62.5 wt%. A comparison between the transfer functions and the response and recovery times of these sensing devices has shown that the structures with ox-SWCNH/SnO₂/PVP = 1/1/1 have the highest relative sensitivities of 0.0022 (mg/L)⁻¹, while the devices with ox-SWCNH/SnO₂/PVP = 2/1/1 have the lowest response time (15 s) and recovery time (50 s) for a room temperature operation, proving the key role of carbonic material in shaping the static and dynamic performance of the sensor. These response and recovery times are lower than those of “heated” commercial sensors. The sensing mechanism is explained in terms of the overall response of a p-type semiconductor, where ox-SWCNH percolated between electrodes of the sensor, shunting the heterojunctions made between n-type SnO₂ or ZnO and p-type ox-SWCNH. The hard–soft acid–base (HSAB) principle supports this mechanism. The low power consumption of these devices, below 2 mW, and the sensing performances at room temperature may open new avenues towards ethanol sensors for passive samplers of environment monitoring, alcohol test portable instruments and wireless network sensors for Internet of Things applications. Full article

Nowadays, the detection of volatile organic compounds (VOCs) at trace levels (down to ppb) is feasible by exploiting ultra-sensitive and highly selective chemoresistors, especially in the field of medical diagnosis. By coupling metal oxide semiconductors (MOS e.g., SnO₂, ZnO, WO₃, CuO, TiO₂ and Fe₂O₃) with innovative carbon-based materials (graphene, graphene oxide, reduced graphene oxide, single-wall and multi-wall carbon nanotubes), outstanding performances in terms of sensitivity, selectivity, limits of detection, response and recovery times towards specific gaseous targets (such as ethanol, acetone, formaldehyde and aromatic compounds) can be easily achieved. Notably, carbonaceous species, highly interconnected to MOS nanoparticles, enhance the sensor responses by (i) increasing the surface area and the pore content, (ii) favoring the electron migration, the transfer efficiency (spillover effect) and gas diffusion rate, (iii) promoting the active sites concomitantly limiting the nanopowders agglomeration; and (iv) forming nano-heterojunctions. Herein, the aim of the present review is to highlight the above-mentioned hybrid features in order to engineer novel flexible, miniaturized and low working temperature sensors, able to detect specific VOC biomarkers of a human’s disease. Full article

We report on the achievement of novel photovoltaic devices based on the pulsed laser deposition (PLD) of p-type Cu₂ZnSnS₄ (CZTS) layers onto n-type silicon nanowires (SiNWs). To optimize the photoconversion efficiency of these p-CZTS/n-SiNWs heterojunction devices, both the thickness of the CZTS films and the length of the SiNWs were independently varied in the (0.3–1.0 µm) and (1–6 µm) ranges, respectively. The kësterite CZTS films were directly deposited onto the SiNWs/Si substrates by means of a one-step PLD approach at a substrate temperature of 300 °C and without resorting to any post-sulfurization process. The systematic assessment of the PV performance of the ITO/p-CZTS/n-SiNWs/Al solar cells, as a function of both SiNWs’ length and CZTS film thickness, has led to the identification of the optimal device characteristics. Indeed, an unprecedented power conversion efficiency (PCE) as high as ~5.5%, a V_OC of 400 mV, a J_SC of 26.3 mA/cm² and a FF of 51.8% were delivered by the devices formed by SiNWs having a length of 2.2 µm along with a CZTS film thickness of 540 nm. This PCE value is higher than the current record efficiency (of 5.2%) reported for pulsed-laser-deposited-CZTS (PLD-CZTS)-based solar cells with the classical SLG/Mo/CZTS/CdS/ZnO/ITO/Ag/MgF₂ device architecture. The relative ease of depositing high-quality CZTS films by means of PLD (without resorting to any post deposition treatment) along with the gain from an extended CZTS/Si interface offered by the silicon nanowires make the approach developed here very promising for further integration of CZTS with the mature silicon nanostructuring technologies to develop novel optoelectronic devices. Full article

We report a phase-pure kesterite Cu₂ZnSnS₄ (CZTS) thin films, synthesized using radio frequency (RF) sputtering followed by low-temperature H₂S annealing and confirmed by XRD, Raman spectroscopy and XPS measurements. Subsequently, the band offsets at the interface of the CZTS/CdS heterojunction were systematically investigated by combining experiments and first-principles density functional theory (DFT) calculations, which provide atomic-level insights into the nature of atomic ordering and stability of the CZTS/CdS interface. A staggered type II band alignment between the valence and conduction bands at the CZTS/CdS interface was determined from Cyclic Voltammetry (CV) measurements and the DFT calculations. The conduction and valence band offsets were estimated at 0.10 and 1.21 eV, respectively, from CV measurements and 0.28 and 1.15 from DFT prediction. Based on the small conduction band offset and the predicted higher positions of the VB_max and CB_min for CZTS than CdS, it is suggested photogenerated charge carriers will be efficient separated across the interface, where electrons will flow from CZTS to the CdS and and vice versa for photo-generated valence holes. Our results help to explain the separation of photo-excited charge carriers across the CZTS/CdS interface and it should open new avenues for developing more efficient CZTS-based solar cells. Full article