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Dye-sensitized solar cells (DSSCs) represent a promising photovoltaic technology for indoor and building-integrated applications due to their colour tunability, semi-transparency, and favourable spectral response. However, the sustainability of conventional devices is hindered by the use of volatile organic solvent-based electrolytes, which raise concerns regarding toxicity, flammability, and long-term stability. This review analyses the evolution of DSSC architecture, with particular focus on electrolyte media, ranging from aqueous systems to deep eutectic solvents and bio-derived quasi-solid architectures. Special attention is focused on the interplay between electrolyte composition, dye design, and interfacial charge-transfer processes. By highlighting recent progress and remaining challenges, this work outlines viable strategies toward safe, durable, and fully sustainable DSSCs tailored for indoor and integrated photovoltaic applications.

Deep Eutectic Solvents (DESs) have been widely used in many fields to exploit their ecofriendly characteristics, from green synthetic procedures to environmentally benign industrial methods. In contrast, their application in emerging solar technologies, where the abundant and clean solar energy is used to properly respond to most important societal needs, is still relatively scarce. This represents a strong limitation since many solar devices make use of polluting or toxic components, thus seriously hampering their eco-friendly nature. Herein, we review the literature, mainly published in the last few years, on the use of DESs in representative solar technologies, from solar plants to last generation photovoltaics, featuring not only their passive role as green solvents, but also their active behavior arising from their peculiar chemical nature. This collection highlights the increasing and valuable role played by DESs in solar technologies, in the fulfillment of green chemistry requirements and for performance enhancement, in particular in terms of long-term temporal stability.

A series of functionalized ferrocene derivatives carrying electron-donor and electron-withdrawing (hetero)aromatic substituents has been designed as potential alternative electrolyte redox couples for dye-sensitized solar cells (DSSC). The compounds have been synthesized and fully characterized in their optical and electrochemical properties. A general synthetic approach that implies the use of a microwave assisted Suzuki coupling has been developed to access a significative number of compounds. The presence of different electron-rich and electron-poor substituents provided fine tuning of optical properties and energy levels. HOMO and LUMO energy values showed that the substitution of one or two cyclopentadienyl rings of ferrocene can be successfully exploited to increase the maximum attainable voltage from a standard DSSC device using TiO2 as a semiconductor, opening the way to highly efficient, non-toxic, and cheap redox shuttles to be employed in solar energy technologies.

Two carbazole-based donor–acceptor dyes, CBZ-Gly and CBZ-EG, featuring glycerol- and ethylene glycol-like side chains, were designed and synthesized to achieve synergistic compatibility with DES-based electrolytes, and systematically investigate their impact on DSSCs performance. These dyes were tested in DSSCs employing two neat deep eutectic solvent (DES) electrolytes (choline chloride/ethylene glycol and choline chloride/glycerol) under both simulated sunlight (AM 1.5G) and indoor lighting (1000 lux). By combining molecular-level dye design with a tailored DES-based electrolyte, we achieved an improvement in long-term device stability over several months and demonstrated a record indoor power conversion efficiency of 9.4%, thereby establishing a new benchmark for fully sustainable, DES-based DSSCs under low-light conditions. Incorporating deep eutectic solvent (DES) mixtures in dye-sensitized solar cells offers an alternative to the use of volatile organic compounds as part of their electrolyte, which limits their use to outdoor environments. Here, the authors design two carbazole-based donor–acceptor dyes that are compatible with DES-based electrolytes and demonstrate their performance under both simulated sunlight and indoor lighting, with enhanced indoor power conversion efficiency under low-light conditions.

The rapid proliferation of internet‐connected devices has transformed our daily habits prompting a shift towards greater sustainability in renewable energy for indoor applications. Among the various technologies available for obtaining energy in indoor conditions, Dye‐Sensitized Solar Cells (DSSCs) stand out as the most promising due to their ability to efficiently convert ambient light into usable electricity. This study explores how the optimal matching of the UV‐Vis absorption spectra of dyes commonly used in DSSCs with the emission profiles of indoor lamps allows for the enhanced efficiency of DSSC under indoor lighting. By testing four organic dyes with different UV‐Vis absorption spectra (L1, Y123, S1, and TP1) under two different common indoor light sources (OSRAM 930 and OSRAM 765 lamp), a significant dye‐lamp correlation was demonstrated. Notably, low‐priced dyes like S1 and TP1, characterized by easier synthetic routes and with an optimal overlap with the dye‐lamp spectrum, exhibited competitive efficiencies, narrowing the performance gap with high‐performing dyes like Y123, which require more demanding preparation approaches. The study highlights the critical importance of tailoring dye selection to specific indoor lighting environments, addressing a significant gap and paving the way for more sustainable and cost‐effective energy solutions for indoor applications. The study highlights the importance of matching dye and light source in optimizing the DSSCs performance under indoor lighting. Improved efficiency is observed when dyes with UV‐Vis spectra match the specific optical characteristics of the light source. The simpler, cost‐effective dye TP1 demonstrated an excellent cost‐performance balance, suggesting that optimal matching allows for high DSSC efficiency while maintaining affordable synthetic accessibility.

Electrochemical nitrogen reduction (E‐NRR) is one of the most promising approaches to generate green NH3. However, scarce ammonia yields and Faradaic efficiencies (FE) still limit their use on a large scale. Thus, efforts are focusing on different E‐NRR catalyst structures and formulations. Among present strategies, molecular electrocatalysts such as metal‐porphyrins emerge as an encouraging option due to their planar structures which favor the interaction involving the metal center, responsible for adsorption and activation of nitrogen. Nevertheless, the high hydrophobicity of porphyrins limits the aqueous electrolyte–catalyst interaction lowering yields. This work introduces a new class of metal‐porphyrin based catalysts, bearing hydrophilic tris(ethyleneglycol) monomethyl ether chains (metal = Cu(II) and CoII)). Experimental results show that the presence of hydrophilic chains significantly increases ammonia yields and FE, supporting the relevance of fruitful catalyst‐electrolyte interactions. This study also investigates the use of hydrophobic branched alkyl chains for comparison, resulting in similar performances with respect to the unsubstituted metal‐porphyrin, taken as a reference, further confirming that the appropriate design of electrocatalysts carrying peripheral hydrophilic substituents is able to improve device performances in the generation of green ammonia. Metal‐porphyrin‐based electrocatalysts bearing peripheral hydrophilic pendants for E‐NRR exhibit enhanced NH3 yields and FE by two to three times compared with the unsubstituted corresponding metal‐porphyrins. This work paves the way for new design strategies for NRR electrocatalysts representing an essential step toward the search for more sustainable alternatives for ammonia production.

Bioactive films composed of Spiro‐OMeTAD, a conductive molecular material (CMM), in combination with collagen have been manufactured and characterised for the first time. In‐vitro cellular testing demonstrated the non‐cytotoxicity of the doped Spiro‐OMeTAD /Collagen films, opening the way for implantable or wearable medical devices and biosensors based on molecular materials. Spiro‐OMeTAD has been used for the first time to prepare a conductive biopolymer with collagen. Stability and electronic properties have been investigated. In‐vitro cellular testing showed the non‐cytotoxicity of films, paving the way for new medical devices and biosensors.

A series of mono- and di-branched donor-π-acceptor charge-separated dyes incorporating triphenylamine as a donor and either Dalton’s or benzothiadiazole group as strong acceptors was synthesized and its fundamental properties relevant to the sensitization of nanocrystalline NiO investigated. The dyes exhibited an intense visible absorption band with a strong charge transfer character favorable to NiO sensitization, shifting the electron density from the donor to the acceptor branches. Nevertheless, the computed exciton binding energy is circa twice that of a common literature standard (P1), suggesting a more difficult charge separation. When tested in p-type dye-sensitized solar cells the dyes successfully sensitized NiO electrodes, with photocurrent densities about half than that of the reference compound. Being recombination kinetics comparable, the larger photocurrent generated by P1 agrees with the superior charge separation capability originating by its smaller exciton binding energy.

Metal–organic frameworks (MOFs) are promising materials for photocatalytic hydrogen production. However, their efficiency is often limited by the optical properties of conventional organic linkers, such as terephthalic acid (TA). In this work, the synthesis of two novel triphenylamine‐based organic dyes (L0‐TA and L1‐TA) featuring a donor–π–acceptor (D–π–A) structure is reported. These dyes are functionalized with a terminal moiety analogous to aminoterephthalic acid, which serves as visible‐light‐absorbing linkers. These dyes retain the coordination ability required for MOF assembly while enhancing light‐harvesting properties. Crystallographic simulations confirm the structural compatibility of these colinkers in hybrid MOFs, providing a viable strategy to maintain MOF crystallinity while improving photocatalytic performance. Triphenylamine‐based dyes L0‐TA and L1‐TA are synthesized and electrochemically characterized to assess their suitability for photocatalytic hydrogen production via water splitting. Crystallographic simulations confirm their structural compatibility with the MIL‐125 framework, allowing incorporation without steric clashes. These findings highlight their potential as photosensitizing linkers in etal–organic framework‐based photocatalytic systems.