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Bifacial (Ag,Cu)(In,Ga)Se₂ (ACIGS) mini-module prototypes employing a high-mobility ITiO transparent back contact are presented. A champion front-side efficiency of 13.5% (14.3% initially, prior to sample shipment) is achieved for a 7.14 cm² aperture-area module without using anti-reflection coatings (ARC), with a bifaciality factor of 76% enabled by the excellent optical transparency of the ITiO film. To boost the open circuit voltage, the absorber is subjected to an RbF post-deposition treatment (PDT). Although the RbF-PDT initially introduces a charge-carrier transport barrier that reduces the fill factor, this penalty is completely eliminated by a heat-light soaking (HLS) treatment. The HLS treatment, however, slightly reduces the rear-side collection efficiency due to a narrowing of the space-charge region. The primary cell-to-module efficiency loss of about 2% points is attributed to a fill-factor reduction from ≈75% to ≈67%. Reference cells using an ITO back contact and a thinner front electrode, fabricated in the same absorber depositions as the corresponding modules, reach efficiencies up to 18% (w/o ARC). Finally, an all-laser-scribed monolithic series interconnection is demonstrated alongside an alternative approach in which the P3 isolation line is defined by a lithography-based process.

The colour coordinates on standard CIE 1931 chromaticity diagrams are presented for NCS (15 soda-15 lime-70 silica (mol%)) glasses, singly and doubly doped with the transition metals (Ti, V, Cr, Mn, Fe, Co, Ni and Cu) at low concentrations (≤1 mol%) and with various rare earth dopants (Ce, Pr, Nd, Sm, Eu, Tb, Dy, Er, Ho). The colour coordinates were calculated from the transmission spectra in turn determined from measured glass absorption spectra. The colour coordinates of 232 glasses are reported, showing which colours can be made with common colouring dopants, and how their coordinates depend on: dopants, concentrations, sample thickness, melting conditions (oxidising electric furnace and reducing gas furnace) and concentrations of agents added to the batch as oxidising (NaNO₃), reducing (C) and/or refining (Na₂SO₄) agents. Cu shows the greatest variability. The varying oxidation states of the dopants and their coordination are the main reasons for colour differences. The effect of the glass thickness in the colour appears because the absorption peaks can be very high and locate partly outside of the visible light range that changes the proportions of the spectrum that stimulate the three colour receptors in the eye.

Purpose

Tandem photovoltaic (PV) devices such as Si/Copper Indium Gallium Selenide (CIGS) tandem architectures have the potential for higher conversion efficiency compared to single-junction silicon modules. This study evaluates the environmental performance of two emerging two-terminal (2T) Si/CIGS tandem architectures: circuitry 2T (C2T) and bonded 2T (B2T). The goal is to quantify their environmental impacts during manufacturing and identify key drivers and improvement opportunities through prospective life cycle assessment.

Methods

An innovative concept designed for tandem solar cells with a 2T approach based on two technologies: Silicon Heterojunction (SHJ) and high bandgap Cu(In, Ga)(Se, S)₂ (CIGS). A cradle-to-gate life cycle assessment was conducted for both C2T and B2T configurations. The study quantified the impacts per 1 kWh of generated electricity and conducted a life cycle impact assessment (LCIA) to identify the environmental hotspots of introduced technologies.

Results and discussion

The LCIA showed GWP values of 0.2203 and 0.1056 kg CO₂-eq/kWh for B2T and C2T, respectively. C2T demonstrated lower environmental impacts due to reduced energy requirements. Silicon solar cell production had the largest contribution across most impact categories. Replacing selenium with sulphur improved the results but the effect was small. Replacing ethyl-vinyl acetate with polyolefins also led to a minor improvement. The prospective analysis shows that under SSP2_RCP1.9 (targeting climate policy for carbon emissions reduction) and strong technological development, emissions fall to 0.014 kg CO₂ eq/kWh for B2T and 0.013 kg for C2T in 2050, representing a 94% and 88% reduction from present values in 2025, respectively.

Conclusions

Si/CIGS tandem technologies present strong potential for combining higher efficiencies with good environmental performance. C2T offers an advantage over B2T due to the absence of bonding materials. Sulphur-containing CIGS absorbers demonstrated the highest efficiency for the required high-bandgap cells, with improved environmental performance. However, several processes remain at low technology readiness levels, leaving room for efficiency improvements.

Recommendations

Further research should explore industrial-scale implementations, evaluate the impacts of energy sourcing by geography, and develop design strategies that balance efficiency gains with minimized environmental footprints. The study suggests that Si/CIGS tandem technologies can be a competitive option among emerging PV solutions, with GWP values falling within the wide range reported for single‑junction silicon PVs. Not only the full process line, but also individual components of the results of the study can be useful for implementation and roll-out. Future research should focus on optimizing material use and reducing process energy consumption without compromising device efficiency.

We developed a computational framework to extract the Raman spectra of nitrogen reduction and ammonia oxidation intermediates on high-entropy alloy (HEA) surfaces, integrating density functional theory with microstructural representations to account for the inherent lattice randomness in these materials. As a case study, we computed the Raman activities of intermediates (N₂*, NNH*, N*, NH*, and NH₃*) and H* adsorption on CoCuFeMoNi HEA surfaces. A comprehensive map of Raman peaks was generated and assigned to specific vibrational modes. The method highlighted the effects of lattice randomness on the Raman spectra compared to those of adsorbates on single-element catalysts. For instance, our results showed that the adsorbed N₂ exhibits Raman modes that are dependent on whether the adsorption is vertical or horizontal. These peak differences could serve as unique fingerprints to identify nitrogen reduction reaction pathways. Moreover, it is also possible to detect surface poisoning by hydrogen, a common issue in reductive environments, due to the high-frequency peaks of H* compared to the typical N-metal stretching and bending frequencies. These results provide valuable references for identifying intermediates in nitrogen reduction and ammonia oxidation reactions, offering insights into reaction mechanisms and potential surface poisoning. This approach is generalizable to other reactions and surfaces in catalysis, provided that the relevant intermediates can be identified.

Al4SiC4 is a ternary wide-band-gap semiconductor with a high strength-to-weight ratio and excellent oxidation resistance. It consists of slabs of Al4C3 separated by SiC layers with the space group of P6(3)mc. The space group allows Si to occupy two different 2a Wykoff sites, with previous studies reporting that Si occupies only one of the two sites, giving it an ordered structure. Another hitherto unexplored possibility is that Si can be randomly distributed on both 2a sites. In this work, we revisit the published ordered crystal structure using experimental methods and density functional theory (DFT). Al4SiC4 was synthesized by high-temperature sintering at 1800 degrees C from a powder mixture of Al4C3 and SiC. Neutron diffraction confirmed that Al4SiC4 crystallized with the space group of P6(3)mc, with diffraction patterns that could be fitted to both the ordered and the disordered structures. Scanning transmission electron microscopy, however, provided clear evidence supporting the latter, with DFT calculations further confirming that it is 0.16 eV lower in energy per Al4SiC4 formula unit than the former. TEM analysis revealed Al vacancies in some of the atomic layers that can introduce p-type doping and direct band gaps of 0.7 and 1.2 eV, agreeing with our optical measurements. Finally, we propose that although the calculated formation energy of the Al vacancies is high, the vacancies are stabilized by entropy effects at the high synthesis temperature. This indicates that the cooling procedure after high-temperature synthesis can be important in determining the vacancy content and the electronic properties of Al4SiC4.

Ammonia is a promising energy vector and can be used as a hydrogen storage medium. Electrocatalytic ammonia syntheses using renewable energy are attractive low-temperature options to the Haber-Bosch high-temperature process, which releases CO₂ in the atmosphere and contributes to the greenhouse effect. High-entropy (HEA) alloys belong to a new class of materials that can provide single-phase stabilizations by mixing different species and are promising candidates to overcome scientific challenges posed by electrochemistry. Lithium-mediated ammonia synthesis is a way to get high-performance ammonia electrosynthesis from nitrogen at room temperature. In this work, we investigated lithium-mediated ammonia synthesis of a thin-film high-entropy catalyst of CoCrFeMnNi.

Electrochromic (EC) technology allows control of the transmission of visible light and solar radiation through thin-film devices. When applied to “smart” windows, EC technology can significantly diminish energy use for cooling and air conditioning of buildings and simultaneously provide good indoor comfort for the buildings’ occupants through reduced glare. EC “smart” windows are available on the market, but it is nevertheless important that their degradation under operating conditions be better understood and, ideally, prevented. In the present work, we investigated EC properties, voltammetric cycling durability, and potentiostatic rejuvenation of sputter-deposited WO₃ thin films immersed in LiClO₄–propylene carbonate electrolytes containing up to 3.0 wt% of ∼7-nm-diameter SiO₂ nanoparticles. Adding about 1 wt% SiO₂ led to a significant improvement in cycling durability in the commonly used potential range of 2.0–4.0 V vs. Li/Li⁺. Furthermore, X-ray photoemission spectroscopy indicated that O–Si bonds were associated with enhanced durability in the presence of SiO₂ nanoparticles.

Tungsten oxide and titanium doped tungsten oxide thin films, deposited by sputtering, were immersed in a viscous electrolyte comprised of LiClO₄ in propylene carbonate and 2.0 wt% of polyethylene oxide (PEO). Electrochromic properties of the films were investigated by electrochemical techniques and in situ transmittance measurements. Cyclic voltammetry data were taken in the voltage ranges 2.0–4.0 and 1.5–4.0 V vs Li/Li⁺ for up to 500 cycles. A potentiostatic rejuvenation treatment was then performed on the degraded electrochromic films, at 6.0 V for 20 h, which was subsequently followed by another cyclic voltammetry measurement. Titanium incorporation into tungsten oxide resulted in a small cyclic stability improvement in the 2.0–4.0-V range, whereas less pronounced effects were observed for cycling in the 1.5–4.0-V range. Combining the results of the present study with our previous work, we are able to assess the relative merits of titanium incorporation and PEO addition to the electrolyte for the durability of electrochromic tungsten oxide thin films. Titanium addition was found advantageous for electrochemical durability in the 2.0–4.0-V range, but no clear benefits of PEO in the electrolyte were seen. On the other hand, in the wider 1.5–4.0-V range, tungsten oxide exhibited better durability than titanium-containing films, and this was especially so after rejuvenation in the PEO-containing electrolyte.

A computational approach to judiciously predict high-entropy alloys (HEAs) as an efficient and sustainable material class for the electrochemical reduction of nitrogen is here presented. The approach employs density functional theory (DFT), adsorption energies of N atoms and N2 molecules as descriptors of the catalytic activity and deep neural networks. A probabilistic approach to quantifying the activity of HEA catalysts for nitrogen reduction reaction (NRR) is described, where catalyst elements and concentration are optimized to increase the probability of specific atomic arrangements on the surfaces. The approach provides key features for the effective filtering of HEA candidates without the need for time-consuming calculations. The relationships between activity and selectivity, which correlate with the averaged valence electron concentration and averaged electronegativity of the reference HEA catalyst, are analyzed in terms of sufficient interaction for sustained reactions and, at the same time, for the release of the active site. As a result, a complete list of 3000 HEAs consisting of quinary components of the elements Mo, Cr, Mn, Fe, Co, Ni, Cu, and Zn are reported together with their metrics to rank them from the most likely to the least likely active catalysts for NRR in gas diffusion electrodes, or for the case where non-aqueous electrolytes are utilized to suppress the competing hydrogen evolution reaction. Moreover, the energetic landscape of the electrochemical NRR transformations are computed and compared to the case of Fe. The study also analyses and discusses how the results would translate to liquid-solid reactions in aqueous electrochemical cells, further affected by changes in properties upon hydroxylation, oxygen, hydrogen, and water coverages.

Making large datasets findable, accessible, interoperable and reusable could accelerate technology development. Now, Jacobsson et al. present an approach to build an open-access database and analysis tool for perovskite solar cells. Large datasets are now ubiquitous as technology enables higher-throughput experiments, but rarely can a research field truly benefit from the research data generated due to inconsistent formatting, undocumented storage or improper dissemination. Here we extract all the meaningful device data from peer-reviewed papers on metal-halide perovskite solar cells published so far and make them available in a database. We collect data from over 42,400 photovoltaic devices with up to 100 parameters per device. We then develop open-source and accessible procedures to analyse the data, providing examples of insights that can be gleaned from the analysis of a large dataset. The database, graphics and analysis tools are made available to the community and will continue to evolve as an open-source initiative. This approach of extensively capturing the progress of an entire field, including sorting, interactive exploration and graphical representation of the data, will be applicable to many fields in materials science, engineering and biosciences.