Rear interface passivation on submicrometer Cu(In,Ga)Se₂ (CIGS) solar cells through nanopatterned dielectric layers has enabled performance gains. The combined optimization of the rear contact interface and the absorber properties enables high-efficiency ultrathin CIGS solar cells. However, the absorber quality of a standard thin 2000 nm CIGS has not been suitably maintained in absorbers with thickness values around 500 nm. Establishing an optimized Na doping, absorber crystallinity, and bandgap profile on such submicrometer CIGS solar cells has been challenging. Moreover, the Na doping may also be influenced by the rear contact architectures implemented in passivated solar cells, e.g., affecting the diffusion of Na from the soda-lime glass. Nonetheless, a proper Na supply into CIGS is critical for an optimized absorber quality. Therefore, this study evaluates the impact of the amount of Na supply controlled through a NaF precursor layer on a rear passivated ultrathin CIGS solar cell. The NaF layer thickness leading to the best performance solar cells in this study, attributed to high absorber crystallinity and low ordered vacancy compound content, is lower than that used in standard thin 2000 nm cells. It suggests that the transition to ultrathin solar cells is not straightforward, and the cell architecture influences the conditions to reach the optimum absorber properties.

Chromium trioxide (hexavalent chromium) is listed as a substance of very high concern in Annex XIV of the REACH Regulation (EC) No 1907/2006. To manage risks and encourage replacement with safer alternatives, its use requires specific authorization. Due to their unique properties, acid baths with hexavalent chromium are widely used to create decorative and functional coatings, and replacing them with a single alternative is challenging. Chromium electroplating using solutions containing trivalent chromium is the most widely analyzed technology cited by applicants seeking authorization for its use as an alternative to chromium deposition from electrolytes containing hexavalent chromium. However, other technologies such as physical vapor deposition, nickel electro/electroless plating, and thermal spraying account for a considerable proportion of the analyzed technologies used to replace hexavalent-chromium-based solutions, as listed by the applicants for authorization. This work briefly reviews the research on the most promising alternatives to conventional chromium electroplating using hexavalent-chromium-containing baths and analyzes the industrial transition towards more sustainable alternatives.

Thin‐film Cu(In,Ga)Se ₂ solar cells are a key photovoltaic technology for addressing global energy and environmental challenges. Reducing absorber thickness lowers manufacturing cost and critical raw material consumption but introduces optical and electrical losses due to incomplete light absorption and increased rear interface recombination. Rear recombination can be mitigated through Ga grading and/or rear contact passivation, for example using tunnel oxide as in c‐Si TOPCon technology. In this work, a full coverage plasma enhanced chemically vapor deposited 8 nm porous SiO _x passivation layer was implemented in ultra‐thin (Ag,Cu)(In,Ga)Se ₂ (ACIGS) solar cells and compared with patterned passivation layers (∼70% coverage) and an unpassivated reference. Standard current‐voltage and external quantum efficiency characterization methods show that the complete passivation yielded the highest performance, achieving 16.4% efficiency, a 2% absolute improvement over the reference. Patterned samples showed enhanced performance to a lower extent. Elemental and structural analysis showed that the SiO _x layers remained intact after 550°C deposition of the 700 nm ACIGS absorber. Notably, a MoSe ₂ interfacial layer formed between the full SiO _x layer and Mo contact, likely due to Na and/or Se diffusion through SiO _x pores. Combining near‐complete passivation and the ohmic MoSe ₂ contact may explain the improved performance.

Building-integrated photovoltaics (BIPV) represents a promising approach for energy generation in urban environments, although balancing aesthetics and photovoltaic performance remains challenging. This work presents and validates a novel tunable coloring strategy for flexible Cu(In,Ga)Se2 (CIGS) solar cells that allows to balance optical induced losses with gains while reducing color angle dependence. Inspired by the light-emitting diode display technology, the strategy combines micropatterned Red, Green, and Blue Bragg reflector (BR) coatings in adjustable proportions to achieve tailored colors. Two line-based microarchitectures were fabricated on soda lime glass and flexible CIGS solar cells. White coloration was selected due to its compatibility with common building facades, with patterns designed to appear visually uniform at distances higher than a 1 m viewing distance. The developed process demonstrated reproducible defect-free microfabrication and successful color perception. Compared to conventional uniform BRs, the RGB pixel coloration strategy significantly reduced color angle dependence and improved optical performance, limiting short-circuit current density losses to below 1.5 mA·cm–2. Moreover, individual color BR led to a short-circuit current loss of 1% to 4% or an enhancement of nearly 10% depending on the final color. The proposed strategy demonstrates strong potential for efficient, aesthetically integrated colored BIPV applications.

Reducing the absorber thickness in thin‐film photovoltaics has a direct impact on low raw material consumption and high manufacturing throughput. However, it leads to low optical performance due to incomplete light absorption. In (Ag,Cu)(In,Ga)Se ₂ (ACIGS)‐based technology, this limitation has been manifested in a photogenerated current density gap between standard and ultrathin devices, hindering their competitiveness and scalability. In this study, it is demonstrated that the optical performance gap of ultrathin ACIGS solar cells to standard devices can be closed by implementing a scalable light management structure at the rear contact. The core of such advancement is a nanoscale‐structured SiO _x periodic array, designed on a transparent rear contact through optical simulations to promote light scattering and increase the optical path length inside the absorber, and developed by a suitable nanoimprint lithography process. This strategy enables 500–600 nm ACIGS solar cells to reach a short‐circuit current density of 36.2 mA cm ⁻² , surpassing 80% of the Shockley–Queisser limit, which has not been reported for such ultrathin devices. The proposed architecture provides gains in bifacial configuration. This way, a fundamental performance limitation of ultrathin solar cells is overcome, enabling material‐efficient and integrated photovoltaic applications.