Search Results (29)

Kesterite (CZTS/CZTSSe) thin-film solar cells are considered an eco-friendly, earth-abundant, and low-cost photovoltaic technology that can fulfill our future energy needs. Due to its outstanding properties including tunable bandgap and high absorption coefficient, the power conversion efficiency (PCE) has reached over 14%. However, toxic cadmium sulfide (CdS) is commonly used as an n-type buffer layer in kesterite thin-film solar cells (KTFSCs) to form a better p–n junction with the p-type CZTS/CZTSSe absorber. In addition to its toxicity, the CdS buffer layer shows parasitic absorption at low wavelengths (400–500 nm) owing to its low bandgap (2.4 eV). For the last few years, several efforts have been made to substitute CdS with an eco-friendly, Cd-free, cost-effective buffer layer with alternative large-bandgap materials such as ZnSnO, Zn (O, S), In₂Se₃, ZnS, ZnMgO, and TiO₂, which showed significant advances. Herein, we summarize the key findings of the research community using a Cd-free buffer layer in KTFSCs to provide a current scenario for future work motivating researchers to design new materials and strategies to achieve higher performance. Full article

This paper details the enhancement of the optoelectronic properties of Cu-(In, Ga)-Se₂ (CIGSe) solar cells through a two-segment process in the ultraviolet (UV)–visible spectral range. These include fine-tuning the DC sputtering power of the absorber layer (ranging from 20 to 40 W at segment I) and thoroughly checking the trace micro-chemistry composition of the absorber layer (CdS, ZnO/CdS, ZnMgO/CdS, and ZnMgO at segment II). After segment I of treatment, the optimal 30 W CIGSe absorber layer (i.e., with a 0.95 CGI ratio) can be obtained, it can be seen that the Cu-rich film exhibits the ability to significantly promote grain growth and can effectively reduce its trap state density. After the segment II process aimed at replacing toxic CdS, the optimal metal alloy (Zn_0.9Mg_0.1O) composition (buffer layer) achieved the highest conversion efficiency (η) of 8.70%, also emphasizing its role in environmental protection. Especially within the tunable bandgap range (2.48–3.62 eV), the developed overall internal and external quantum efficiency (IQE/EQE) is significantly improved by 13.15% at shorter wavelengths. A photovoltaic (PV) module designed with nine optimal CIGSe cells demonstrated commendable stability. Variation remained within ±5% throughout the 60-day experiment. The PV modules in this study represent a breakthrough benchmark toward a significant advance in the scientific understanding of renewable energy. Furthermore, this research clearly promotes the practical application of PV modules, harmonizes with sustainable goals, and actively contributes to the creation of eco-friendly communities. Full article

The electrodeposition of ZnO films was studied using potentiostatic mode in varying conditions including the presence of graphene oxide (GO) as a buffer layer and an additional deposition step. The obtained films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform Infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The effect of electrodeposition conditions on the adsorption and photocatalytic properties of ZnO nanostructured films was analyzed by using methylene blue (MB) as a model dye molecule and exposure to UV light. The results indicated a marked effect of GO content in the buffer layer and the duration of nucleation on the properties of electrodeposited ZnO films. Lower GO content and an additional deposition step of 60 s resulted in the best adsorption and photocatalytic activity, these being 7 and 5-folds, respectively, in comparison to ZnO in absence of these adjustments. The MB photodegradation was found to follow first-order kinetics, the rate constant reaching a value of 2.38 × 10⁻³ min⁻¹. Full article

Cu-In-Ga-Se nanoparticles (NPs) were synthesized using a colloidal route process. The effects of growth temperature (GT) on the properties of CuInGaSe2 (CIGS) thin films made from these nanoparticles were investigated using TEM, PL, XRD, and SEM techniques. The Cu-In-Ga-Se NPs were synthesized at growth temperatures ranging from 90 °C to 105 °C and then annealed at 550 °C for 7 min under a Se ambient. The resulting CIGS thin film, formed from Cu-In-Ga-Se NPs synthesized at a GT of 90 °C (referred to as GT90-CIGS), showed a tetragonal structure, large grain size, and high sunlight absorption. It had a band gap energy (Eg) of approximately 0.94 eV. Non-vacuum GT90-CIGS-based solar cells were investigated and fabricated using varying thicknesses of a CdS buffer layer. The maximum power conversion efficiency achieved was approximately 8.3% with an optimized device structure of Al/ITO/ZnO/CdS/CIGS/Mo. Full article

Cu₂ZnSnS₄ (CZTS) is a promising absorber material to produce thin film solar cells thanks to its high absorption coefficient, low cost and low toxicity. CdS is commonly used as a buffer layer for CZTS solar cells but, beyond its toxicity, it has a nonoptimal band alignment with CZTS. Zn_xSn_1−xO (ZTO), based on earth-abundant and nontoxic elements and with a large and tunable band gap, is a suitable alternative buffer layer. In this paper, the atomic layer deposition (ALD) of ZTO was employed by testing different compositions and thicknesses. ALD not only leads to very compact and homogenous ZTO layers (enabling tuning the stoichiometry of the ZTO so prepared) but also makes the i-ZnO layer (usually sandwiched between the buffer layer and the transparent contact) redundant and detrimental. Through SCAPS simulation and impedance measurements, the ZnSnO/AZO interface impact on the Cd-free kesterite solar cells’ performances has been investigated, highlighting its leading role in achieving an effective charge extraction and the detrimental effect of the i-ZnO layer. With this approach, a solar cell based on an architecture simpler and more eco-friendly than the conventional one has been produced with comparable efficiencies. Full article

Zn alloys have lately captivated the attention of the scientific community as possible materials for cardiovascular applications, showing a corrosion behavior and mechanical properties in between of those of Mg and Fe alloys. To better understand the different aspects of the interaction of Zn with body fluids, the basic corrosion pattern and the degradation products’ formation were investigated considering the effect of CO₂ amount in the atmosphere and different pseudo-physiological media; that is Hanks’ balanced salt (HSS), Dulbecco’s phosphate-buffered saline (PSS) and physiological saline solution (NSS), through a 14-day static immersion study. A mixed degradation layer mainly composed of ZnO with Zn₃(PO₄)₂·4H₂O and Zn(CO₃)₂ precipitates was found on surfaces immersed in both HSS and PSS, independently of the atmosphere, while a ZnO/ZnCl₂ layer was found on the surface immersed in NSS, which also revealed the higher corrosion rate due to the effect of Cl⁻ ions. Samples tested under a CO₂-rich atmosphere showed a more compact passivating layer, higher dimensions crystals and less cavities when tested in HSS, PSS and NSS, respectively. Full article

Flexible CZTSSe solar cells have attracted much attention due to their earth-abundant elements, high stability, and wide application prospects. However, the environmental problems caused by the high toxicity of the Cd in the buffer layers restrict the development of flexible CZTSSe solar cells. Herein, we develop a Cd-free flexible CZTSSe/ZnO solar cell. The influences of the ZnO films on device performances are investigated. The light absorption capacity of flexible CZTSSe solar cells is enhanced due to the removal of the CdS layer. The optimal thickness of the ZnO buffer layers and the appropriate annealing temperature of the CZTSSe/ZnO are 100 nm and 200 °C. Ultimately, the optimum flexible CZTSSe/ZnO device achieves an efficiency of 5.0%, which is the highest efficiency for flexible CZTSSe/ZnO solar cells. The systematic characterizations indicate that the flexible CZTSSe/ZnO solar cells based on the optimal conditions achieved quality heterojunction, low defect density and better charge transfer capability. This work provides a new strategy for the development of the environmentally friendly and low-cost flexible CZTSSe solar cells. Full article

Copper–indium–gallium–diselenide Cu(In,Ga)Se₂ (CIGS) is a semiconductor compound belonging to group I-III-VI, with a chalcopyrite crystal structure. CIGS is promising for the development of high-performance photovoltaic applications in terms of stability and conversion efficiency. It is one of the main candidates to rival the efficiency and stability of conventional crystalline silicon cells, due to its high light absorption coefficient, lower material cost, and high stability. The limitation of its use is that CIGS integrates indium (In) and gallium (Ga), which are rare and expensive materials. The amount of these materials in the CIGS cell can be reduced by optimizing the thickness of the absorber. We show that the introduction of a layer of highly doped silicon in the structure of the solar cell between the absorber layer and the back surface field layer effectively allows for decreasing the thickness of the absorber. Within the same objective, we focus on the danger of cadmium in the CdS buffer layer. In the first optimizations, we replaced the n-type CdS buffer layer with a n-type Zn(O,S) buffer layer. For this work, we used a one-dimensional simulation program, named Solar Cell Capacitance Simulator in one Dimension (SCAPS-1D), to investigate this new CIGS solar cell structure. After optimization, a maximum conversion efficiency of 24.43% was achieved with a 0.2 μm CIGS absorber layer and a 1 µm Si BSF layer. Full article

CdxTeyOz/CdS/ZnO heterostructures were obtained by the SILAR method using ionic electrolytes. A CdS film was formed as a buffer layer for better adhesion of the cadmium-tellurium oxides to the substrate surface. In turn, the ZnO substrate was previously prepared by electrochemical etching to form a rough textured surface. In addition, an annealing mode was used in an oxygen stream to complete the oxidation process of the heterostructure surface. The resulting nanocomposite was investigated using RAMAN, XRD, SEM, and EDX methods. We assume that the oxides CdO and TeO₄ initially form on the surface and later evolve into TeO₂ and TeO₃ when saturated with oxygen. These oxides, in turn, are the components of the ternary oxides CdTeO₃ and CdTe₃O₈. It should be noted that this mechanism has not been fully studied and requires further research. However, the results presented in this article make it possible to systematize the data and experimental observations regarding the formation of cadmium-tellurium films. Full article

High open-circuit voltage in Sb₂Se₃ thin-film solar cells is a key challenge in the development of earth-abundant photovoltaic devices. CdS selective layers have been used as the standard electron contact in this technology. Long-term scalability issues due to cadmium toxicity and environmental impact are of great concern. In this study, we propose a ZnO-based buffer layer with a polymer-film-modified top interface to replace CdS in Sb₂Se₃ photovoltaic devices. The branched polyethylenimine layer at the ZnO and transparent electrode interface enhanced the performance of Sb₂Se₃ solar cells. An important increase in open-circuit voltage from 243 mV to 344 mV and a maximum efficiency of 2.4% was achieved. This study attempts to establish a relation between the use of conjugated polyelectrolyte thin films in chalcogenide photovoltaics and the resulting device improvements. Full article

The vacuum-free quantum dots solar cell (VFQDSC) was fabricated without using any vacuum process. The spherical iron pyrite (FeS₂) nanoparticles (SNPs) and ZnO nanoparticles (NPs) were synthesized and characterized. In the device structure, FeS₂ SNPs were used as an acceptor material (n-type), and the low band gap polymer of poly[4,8-bis(2-ethylhexyloxyl)benzo[1,2-b:4,5-b′]-dithiophene-2,6-diyl-alt-ethylhexyl-3-fluorothieno[3,4-b]thiophene-2-carboxylate-4,6-diyl] (PBT7) was used as a donor material (p-type). In this study, we first applied the graphene oxide (GO) as the hole transport buffer layer (HTBL) and zinc oxide (ZnO) as an electron transport buffer layer (ETBL), which were considered to improve the charge transportation efficiency of the device’s system. The device with the structure of the Glass/ITO/HTBL/FeS₂ SNPs, PBT7/ ETBL/E-GaIn were fabricated with a maximum power conversion efficiency (PCE) of 3.6%. Full article

We studied the texturing, roughness, and morphology features of ZnO films grown on the R (1$\overline{1}$02)-, M (10$\overline{1}$0)-, A (11$\overline{2}$0)-, and C (0001)-planes of sapphire, as well as their optical and luminescent properties. We showed that the growth conditions, substrate orientation, and the presence of a buffer layer significantly affected the structure and morphology of the growing films, which was reflected in their optical and radiative properties. In particular, films grown on the A- and M- planes of sapphire showed the highest UV radiation brightness values and exhibited stimulated emissions upon pulsed photoexcitation. The dependence of the topography of the film surface on the substrate orientation allowed the formation of a smooth continuous film with pronounced interference properties using the R- and M- planes of sapphire. A change in the crystallographic orientation, as well as a significant enhancement in crystallinity and luminescence, were observed for ZnO films grown on R-plane sapphire substrates with a gold buffer layer as compared to films grown on bare substrates. At the same time, the use of gold facilitates a significant smoothing of the film’s surface, retaining its interference properties. The sensitivity of interference and laser properties to changes in the external environment, as well as the ease of fabrication of such structures, create prospects for their application as key elements of optical converters, chemical and biological sensors, and sources of coherent radiation. Full article

Third-generation thin-film solar cells based on CZTSSe are highly promising because of their excellent optoelectrical properties, earth-abundant, and non-toxicity of their constituent elements. In this work, the performance of CZTSSe-based solar cells with TiO₂, CdS, and ZnSe as electron transporting materials (ETMs) was numerically investigated using the Solar Cell Capacitance Simulator (SCAPS). The effect of the active layer’s thickness and electron affinity, different buffer layers, and the contour plot of the operating temperature versus thickness of the CdS buffer layer were studied. The results show that the optimum power conversion efficiency for CdS, TiO₂, and ZnSe, as the ETMs, is 23.16%, 23.13%, and 22.42%, respectively. Full article

The different size of plasmonic gold nanorods (NRs) were synthesized by the overgrown seeds method and applied to vacuum-free hybrid solar cells (VFHSCs). Tin disulfide (SnS₂) quantum dots were synthesized and used as an n-type material of the device. The synthesized materials were characterized by different techniques such as transmission electron microscopy (TEM), UV-Vis spectroscopy, and atomic force microscopy (AFM). The Au (NRs) had a different of size of NR1 (Width: 4 nm; Length: 12 nm), NR2 (Width: 5 nm; Length: 16 nm), NR3 (Width: 6 nm; Length: 22 nm) which were measured using a TEM technique. The Au NR particles were incorporated into the PEDOT:PSS as a hole transport layer (HTL) of solar cells device. The effects of Au NRs size on the device performance were investigated. A thin film of Zin oxide (ZnO) was used as a buffer layer of the device. The influence of buffer layer thickness on the device’s active layer surface morphology was also studied. At the optimized condition, the highest power conversion efficiency was obtained at about ~3.7%. Full article

The numerical modeling of a copper zinc tin sulfide (CZTS)-based kesterite solar cell is described in detail in this article. To model FTO/ZnO/CdS/CZTS/MO structured solar cells, the Solar Cell Capacitance Simulator-one-dimension (SCAPS-1D) program was utilized. Numerical modeling was used to estimate and assess the parameters of various photovoltaic thin film solar cells. The impact of different parameters on solar cell performance and conversion efficiency were explored. Because the response of a solar cell is partly determined by its internal physical mechanism, J-V characteristic characteristics are insufficient to define a device’s behavior. Regardless of the conviction in solar cell modeling, variable attributes as well as many probable conditions must be handled for simulation. Promising optimized results were obtained with a conversion efficiency of ($\eta$% = 25.72%), a fill factor of (FF% = 83.75%), a short-circuit current of ($J_{SC }$ = 32.96436 mA/cm²), and an open-circuit voltage of ($V_{OC}$ = 0.64 V). The findings will aid in determining the feasibility of manufacturing high-efficiency CZTS-based solar cells. First, in the SCAPS-1D environment, the impacts of experimentally constructed CZTS solar cells were simulated. The experimental data was then compared to the simulated results from SCAPS-1D. After optimizing cell parameters, the conversion efficiency of the improved system was observed to rise. The influence of system factors, such as the thickness, acceptor, and donor carrier concentration densities of the absorber and electron transport layers, and the effect of temperature on the efficiency of CZTS-based photovoltaic cells, was explored using one-dimensional SCAPS-1D software. The suggested findings will be extremely useful to engineers and researchers in determining the best method for maximizing solar cell efficiency, as well as in the development of more efficient CZTS-based solar cells. Full article