Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) is an attractive thin-film absorber based on earth-abundant and low-toxicity elements. Nevertheless, high-performance CZTSSe solar cells still typically employ CdS buffer layers, which pose significant limitations due to the hazardous nature of Cd and introduce parasitic absorption at short wavelengths. The use of alternative buffer layers is therefore crucial for further advancing this technology. Among the possible candidates, ZnxSn1−xO (ZTO) has emerged as a promising option due to its wide, tunable bandgap and benign constituents. In this work, ZTO buffer layers were deposited by Atomic Layer Deposition (ALD) at three different temperatures (150, 120, 90 °C). However, the as-deposited ZTO films exhibited high resistivity, which was mainly attributed to the controversial role of defect-related intragap states. To overcome this limitation, complete photovoltaic (PV) devices were annealed in air at 260 °C and subsequently exposed to light soaking. These post-deposition treatments synergistically improved the electrical conductivity of ZTO and reduced trap-assisted recombination, thereby enhancing final PV performance. Optical characterisation revealed a widened bandgap compared to conventional CdS, effectively suppressing parasitic absorption in the blue spectral region and enhancing short-circuit current density (JSC) as expected. The best-performing devices were obtained with ZTO deposited at 90 °C, yielding efficiencies (η) exceeding 7% by optimising the trade-off between junction quality and ZTO conductivity. These experimental findings are corroborated by numerical SCAPS simulations and confirm the potential of ALD-grown ZTO as a Cd-free buffer layer for kesterite solar cells.

Integrating photovoltaics into buildings, parking shelters, street furniture, and crops can support the transition to sustainable electricity management. Yet, these devices must manage light to generate energy while ensuring visual comfort before being launched to market. Here, semi-transparent perovskite solar cells (PSCs) in n-i-p architecture have been engineered to meet the requirements for adequate transparency while maintaining high power conversion efficiency. The atomic layer deposited TiO2 compact layer outperformed the traditional spray pyrolysis one thanks to minimised parasitic absorptions and prevented shunt paths. Additionally, to ensure efficient transmittance in the visible light range, the halide perovskite composition is based on a mixture of Cs and formamidinium, yielding a high quality, amber coloured light absorber that reduces glare. Even though the devices studied here employed a semi-transparent gold rear electrode, they achieved an average visible transmittance (AVT) of 7.49%, a power conversion efficiency (PCE) of 13.41%, and a light utilisation efficiency (LUE) of 1.00%. The rear contact remains the primary optical constraint, but the front-end architecture developed wants to serve as a robust model to push further development. By combining this optimized front end with emerging transparent rear electrodes, the potential of semi-transparent PSCs can be unlocked.

Abstract Among emerging thin-film solar cells, kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) absorbers offer several advantages: they are based on earth-abundant, non-toxic elements and combine high stability, tunable bandgap (E g ), and flexibility, key features for integrated photovoltaic (PV) applications. Selenium-rich CZTSSe (E g of 1.1 eV) is an ideal bottom-cell candidate for flexible tandem devices with perovskites, thereby maximising efficiency. However, CZTSSe/perovskite tandems are still underexplored. Here, we report an effective solution - based route for producing high-efficiency CZTSSe bottom cells on both rigid Mo-coated soda-lime-glass and flexible Mo-foil substrates. To optimise absorber morphology and grain size, Na-doping and Ag-alloying were performed. Then, 4-Terminal (4T) tandem devices combining kesterite- and perovskite-based subcells were designed. Solution-processed Cs 0.17 FA 0.83 Pb(I 0.90 Br 0.10 ) 3 perovskites (E g of 1.63 eV) ensured optimal bandgap matching and broadened light harvesting, yielding efficiencies exceeding 22% and 20% for rigid and flexible 4T tandem devices, respectively. This proof-of-concept solution-processed tandem approach represents a promising step toward developing cost-effective and sustainable PV technologies, with promising results for future solar energy applications.

Cu2ZnSn(S,Se)4 (CZTSSe or kesterite) is an emerging inorganic light absorber with a bandgap of 1.0- 1.5 eV, ideal for efficient solar spectrum harvesting. This material can be grown on both rigid and flexible substrates, standing as one of the most promising candidates for Integrated Photovoltaics. Solution-based methods are currently the best choice for CZTSSe synthesis, relying on the deposition of multiple layers. The most widely used techniques are blade coating, spray pyrolysis, dip coating, and spin coating, with the latter achieving the highest efficiencies. However, this technology's small-area limitations and large precursor waste still hinder the kesterite solar cells' scalability. In contrast, drop-on-demand inkjet printing is a promising and industrially appealing solution-based technique suitable for processing large areas. To date, it has been tested in a few cases, yielding encouraging results with rigid solar devices; however, it has never been used to fabricate flexible CZTSSe solar cells. In this work, we report on the first-time realization of inkjet-printed flexible kesterite solar cells. The resulting devices exhibit an efficiency enhancement over our spin-coated references, driven by improved film crystallinity, reduced shunting, and enhanced fill factor. The inkjet-printed flexible champion device achieved an efficiency of 10.4%, outperforming our spin-coated reference counterpart. Structural, morphological, and optoelectronic analyses confirm the superior quality of the inkjet-deposited absorber. This scalable, solution-based approach establishes a pathway for the roll-to-roll fabrication of earth-abundant, lightweight kesterite photovoltaics for next-generation, integrated, and flexible photovoltaic applications, a key factor for the advancement of kesterite materials in the photovoltaic sector. (c) 2026 The Authors. Published by Published by Elsevier B.V. and Science Press on behalf of Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Cu _2 MnSnS _4 (CMTS) is regarded as an emerging absorber for thin-film photovoltaic (PV) devices. In this work, CMTS thin films prepared using a low-cost, straightforward solution-based technique were extensively characterized, and the results were correlated with the preparation conditions and corresponding PV performances. X-ray diffraction techniques have been used to study crystallographic structure and microstructural parameters, while energetic band positions were depicted exploiting photoelectron yield spectroscopy and Kelvin probe measurements. The importance of fine-tuning the composition of the starting solution and the beneficial effect of post-deposition treatments were consequently highlighted. A strategy of slow cooling after annealing was studied, resulting in a new record for wet-prepared CMTS, with a champion device yielding 0.97% efficiency 5 months after the first PV measurement. Factors responsible for the typical modest efficiencies of CMTS have been investigated: photoluminescence revealed the presence of intra-gap defects, magnetic characterization revealed room-temperature short-range magnetic ordering, and electrical transport and thermal measurements highlighted a semimetallic-like character, all of which are barriers to achieving high PV performance in CMTS-based devices. Moreover, magnetometry indicates a weakly ordered spin-glass-like state, providing insight into the electronic correlations underlying the observed transport behavior.

Perovskite solar cells (PSCs) have burst into photovoltaic (PV) research, revolutionising it and demonstrating that they can achieve performances comparable to technologies already on the market. Despite that, the major limitation of PSCs' commercialisation is their poor environmental stability. Inorganic carriers transporting materials have gained attention for enhancing PSCs' durability due to their superior stability and non-hygroscopic nature. Among them, kesterite Cu2ZnSnS4 (CZTS) is a promising inorganic hole transporting material (HTM) thanks to its optimal electronic properties, non-toxic, abundant elements, and simple solution deposition methods. Herein, the effect on the stability of inverted PSCs employing CZTS nanoparticles (NPs) as HTM is investigated by X-ray photoelectron and ultraviolet photoelectron spectroscopy, together with steady-state and time-resolved photoluminescence spectroscopies. Special attention was given to the alteration in the PV performances over time of the CZTS-based device compared to a control device with a common organic HTM. The enhanced stability of the CZTS NPs-based devices in opposition to degradation of the devices with a [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) self-assembled monolayer as HTM was demonstrated through solar simulator measurements and external quantum efficiency. The efficiency of a CZTS-based p-i-n PSC increased by 34% after three weeks, while the efficiency of the organic HTM-based device decreased by 16% during the same period. Furthermore, CZTS-based PSCs showed a drop-in efficiency of 80% after four days under a humidity test at 70% RH, while the efficiency of the organic HTM-based devices dropped by 80% after two days under the same conditions. Moreover, analysis of the photoluminescence spectra reveals no modification of the CZTS-based PSCs.

Kesterites, Cu2ZnSn(S,Se)4, are known for their photovoltaic (PV) application as an emerging thin-film chalcogenide solar device technology, and show high cost-effectiveness thanks to low production costs, earth-abundance and non-toxicity of their composing elements. Their solution-based synthesis makes them suitable also for flexible and Product-Integrated PV. Besides, their properties (such as energy gap, transparency, resistance, charge carrier density, and mobility) can be tuned by partial or complete substitution of one or more components allowing their employment also in tandem solar architectures. Here we report on a facile and straightforward process for the production of low-cost flexible kesterite solar cells based on wet methodologies, starting from a precursor ink deposited through blade coating. Thanks to back-contact engineering the flexible devices reached and then overcame the performances of their rigid original counterpart.

Flexible CZTSSe (Cu2ZnSn(S,Se)(4)) solar cells on flexible molybdenum foil (MF) substrates are showing promise for being a candidate for the next-generation large-area and lightweight solar technologies. However, the nature of the back contact continues to be a decisive factor influencing absorber morphology, crystallinity, and the ultimate final device performance. In this work, we provide a comprehensive analysis and comparison of a variety of back contact configurations of flexible and rigid Mo substrates. We analyze four configurations in detail: MF, sputtered Mocoated MF, 10 nm NaF-coated MF, and MoOx-interlayered MF. We compare these with standard rigid devices on sputtered Mo on soda-lime glass (SLG) substrates. The work examines the impact of each back contact on the CZTSSe absorber growth behavior based on grain size, grain distribution, and defect passivation. Furthermore, solar devices are also prepared and examined to find the impact of back contact engineering on the main performance characteristics.

Several studies were carried out to monitor and reduce the presence of diclofenac in the environment. Some of them reported an abatement of the drug of only 20–40%, whereas others based on advanced oxidation processes or photocatalytic methods mediated by TiO 2 often highlighted high energy cost requirements and the formation of byproducts whose toxicity was higher than that of diclofenac. This study concerns both the photolytic and the photocatalytic degradation of diclofenac in aqueous media to evaluate its partial or total elimination and the formation of the transformation products, whose toxicity has been investigated. For this purpose, an ultra-high-performance liquid chromatography coupled with a high-resolution quadrupole time-of-flight-mass spectrometry method was used to elucidate the transformation products following a non-targeted approach based on mass data-independent acquisition. Twelve different transformation products were identified, two of them (TP1 and TP4) for the first time, and accordingly elucidated. Based on the accurate tandem mass spectrometry information acquired, a photodegradation mechanism was proposed. A toxicity assessment of the photoproducts was performed by in silico method. Although UV–vis photolysis degradation alone can abate the diclofenac after 120 min of irradiation, the formed transformation products persist at the end of the degradation, and they are mainly carbazole derivatives with comparable toxicity and similar persistence in the environment to that of diclofenac. On the contrary, the use of quaternary chalcogenide nanoparticles (Cu 2 ZnSnS 4 ) is a successfully promising process for the drug photodegradation, resulting in the elimination of diclofenac and the formation of less toxic products than diclofenac at the end of degradation.

Copper zinc tin sulfide (commonly known as CZTS) solar cells (SCs) are gaining attention as a promising technology for sustainable electricity generation owing to their cost-effectiveness, availability of materials, and environmental advantages. The goal of this study is to enhance CZTS SC performance by adding a back surface field (BSF) layer. SC capacitance simulator software (SCAPS) was used to examine three different configurations. Another option is to replace the cadmium sulfide (CdS) buffer layer with a titanium dioxide (TiO2) layer. The results demonstrate that the reduced graphene oxide (rGO) BSF layer increases the conversion efficiency by 25.68% and significantly improves the fill factor, attributed to lowering carrier recombination and creating a quasi-ohmic contact at the interface between the metal and semiconductor. Furthermore, replacing the CdS buffer layer with TiO2 offers potential efficiency gains and mitigates environmental concerns associated with the toxicity of CdS. The results of this investigation could enhance the efficiency and viability of CZTS SCs for future energy applications. However, it is observed that BSF layers may become less effective at elevated temperatures due to increased recombination, leading to reduced carrier lifetime. This study underlines valuable insights into optimizing CZTS SC performance through advanced material choices, highlighting the dual benefits of improved efficiency and reduced environmental impact.

The incorporation of selenium into the CdTe has recently enhanced the performance of the solar cells to 23.1 %. The narrower band gap of the CdSeTe/CdTe absorber boosts the short-circuit current density; also, Se introduction increases the carrier's lifetime. Optimizing CdSexTe1-x band-grading is crucial for achieving highperformance CdTe photovoltaics. Another current goal is to reduce the thickness of the absorber to further reduce production costs and environmental impact. Thus, studying the effects of Se introduction in ultra-thin CdTe absorbers is essential. To investigate Se concentration's impact on ultra-thin CdTe, we fabricated CdSeTe/CdTe devices with an absorber thickness of 0.8 mu m by depositing different CdSe/CdTe ratios. Our 0.8 mu m thick cells have currently achieved an efficiency of 12.8 %, but most important this study shows that Se introduction in ultra-thin CdTe results in structural properties different from those of thicker absorbers, impacting the device performance.

Kesterite solar cells are pivotal in advancing flexible photovoltaic devices integrated into buildings and products. High-purity Mo foil is one of the most promising flexible substrates, thanks to its outstanding properties. However, the kesterite/Mo foil interface is extremely reactive and chemically unstable during the high-temperature selenization process required to obtain the kesterite crystalline phase, forming a thick MoSe2 layer. The role of MoSe2 in kesterite solar cells is still under discussion, as it can affect the charge extraction at the back contact and the kesterite grain growth. This work reports on the functionalisation of Mo foil to fabricate flexible kesterite solar cells based on Li-doped and Ag-alloyed Cu2ZnSn(S,Se)4 (Li-ACZTSSe) films grown using the molecular ink method. MoS2, Al2O3, MoO2, and MoO3 were inserted between the precursor layer and the substrate to investigate their impact on the MoSe2 thickness, the morphology and composition of the absorber, interface chemistry, carrier collection at the back contact, and the related photovoltaic parameters. It is demonstrated that MoO3 as an interlayer significant enhances device performance by improving the absorber quality and back contact, achieving an efficiency of 11.2% with a 15 mu m thick MoSe2 layer. To the best of our knowledge, this is the first report demonstrating that an over-thick MoSe2 layer is not significantly detrimental to the performance of flexible kesterite-based devices when the Li-ACZTSSe crystallinity and grain growth are improved and its decomposition at the back is prevented.

We are all users of lithium-ion batteries (LIBs), the electrochemical energy storage devices that revolutionized our life, making the diffusion of portable and wearable devices possible and now driving the switch from a combustion engine to electric vehicles in the transportation sector. These positive trends are however leading to two whiplash effects: the issue related to management of LIBs when they reach the end of their life (EoL-LIBs) and the supply of the critical raw materials (CRMs) needed to produce the essential LIBs' components. Recycling of EoL-LIBs is the answer to these two problems, addressing the aspects of waste management while providing a secondary source of CRMs needed to produce new LIBs, in a closed-loop circular economy scheme. The proposed laboratory activity is specifically focused on the recycling of LiCoO2, the most diffused cathode material and also the one containing the highest amount of CRMs. The students will be called to analyze the degradation procedure through acidic leaching, comparing the method today mostly exploited at industrial level (using inorganic acid) and the method recently proposed in the scientific literature (exploiting organic acids). Students will be called to consider not only quantitative chemical indicators (yields of degradation and recovery of CRMs) but also the cost, safety, and disposal of the procedure. The aim of this experience is to drive the students to critically consider all aspects related to sustainability, to present them the tools to quantitatively assess it, and to create awareness regarding a technology involved in our everyday life.

Dangerous emerging water micropollutants like Diclofenac are harming ecosystems all over the planet, and immediate action is needed. The large bandgap photocatalysts conventionally used to degrade them need to be more efficient. Cu2ZnSnS4, a well-known light absorber in photovoltaics with a bandgap of 1.5 eV, can efficiently harvest an abundant portion of the solar spectrum. However, its photocatalytic activity has so far only been reported in relation to the degradation of organic dyes, and it is usually used as a benchmark to assess the activity of a photocatalyst without testing its actual potential on a hazardous water micropollutant conventionally encountered in primary and secondary waters. Here, we report the promising photocatalytic activity of Cu2ZnSnS4 nanoparticles in the degradation of Diclofenac, chosen as a benchmark for dangerous emerging water micropollutants.

The manganese-based quaternary chalcogenide Cu 2 MnSnS 4 could have the chance to promote the production of sustainable solar cells, but the reported photovoltaic efficiencies are still too poor to push the research on the topic. Herein, a low-cost, straightforward, and sustainable wet methodology to synthesise Cu 2 MnSnS 4 thin films is reported. The main issues that hindered their power conversion efficiencies have been investigated. Firstly, the manganese oxidation state has been stabilised by fine-tuning the synthesis parameters. Cu 2 MnSnS 4 was obtained in the crystalline structure of stannite, and no oxygen was found in the material bulk. Prototype devices in substrate configuration were produced, and the new record efficiency ( eta = 0.92 %) for wet-synthesised Cu 2 MnSnS 4 was reached. Since the photovoltaic performances were poor despite the high quality of Cu 2 MnSnS 4 produced, the interface between the light absorber material and the buffer layer, CdS, was investigated, and its suitability to work as an efficient photovoltaic p-n junction was evaluated. We reveal that the buffer layer deposition procedure highly impacts the composition of the Cu 2 MnSnS 4 surface, and that band alignment between Cu 2 MnSnS 4 and CdS is unfavourable. The statements have been sustained by X-ray diffraction and Raman analysis, X-ray and ultraviolet photoelectron, electron paramagnetic resonance, and energy dispersive X-ray spectroscopies.

In the scenario of the new emerging photovoltaics, kesterites play a lead role in the thin-film solar cell technologies. This class of compounds, mainly represented by the pure-sulfide form Cu2ZnSnS4 (CZTS) and the sulfo-selenide form Cu2ZnSn(S,Se)4 (CZTSSe), shows unique characteristics and stands as a promising p-type absorber material thanks to its high absorption coefficient, high cost-effectiveness and low toxicity. However, CdS is commonly used as the n-type partner (buffer layer) in kesterite solar cells but, beyond its toxicity, it has a nonoptimal band alignment with kesterites and exhibits parasitic absorption at low wavelengths due to its bandgap. Several efforts have been made in the last decade, to replace CdS with a suitable, Cd-free, both environmentally and economically sustainable buffer layer, and many times with successful results allowing not only to equal, but also to overcome in few cases the performances of the corresponding CdS-based reference devices. Zn1-xSnxO for instance leads to higher efficiencies than CdS when coupled with pure-sulfide CZTS, while Zn(O,S) seems to couple better with CZTSSe. TiO2 has been also considered as suitable buffer layer for kesterites and, in the last few years, several works have been reported both theoretical and experimental, showing very promising results. In this review we summarize the efforts and the improvements recorded by the scientific community working on this topic in the last ten years, with the aim to supply a landmark useful to design future experiments in a more efficient way and to push forward the related research activities, in order to fully overcome CdS limitations and to promote thin-film kesterite devices to higher performances.

Cu2ZnSnS4 (CZTS) is a narrow band gap, non-toxic, and environmentally friendly semiconductor with important properties for photovoltaic and electro-/photo-catalytic applications. In this study, we report on the synthesis of CZTS nanoparticles (NPs) by a simple and promising hot-injection technique using environmentally friendly, earth-abundant, and low-cost copper and zinc acetates in combination with tin chloride and elemental sulphur. Oleylamine was used as solvent and capping agent. The influence of injection temperatures on the crystalline size, morphology and crystal structure were studied. The formation of detrimental phases has been investigated, as well as their removal by using an HCl treatment during the purification step of the CZTS NPs synthesis process. Raman spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) analyses were used to investigate the formation mechanism of the CZTS NPs. The experimental results showed that the injection temperature influences the NPs growth. Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR-ATR) analyses were used to confirm the removal of both organic traces and detrimental phases. It was found that HCl treatment plays a key role in the successful removal of impurities without altering the final crystalline composition profile or NPs surface.