Sensitizers for Aqueous-Based Solar Cells

Exploring zinc oxide morphologies for aqueous solar cells by a photoelectrochemical, computational, and multivariate approach

Dye-sensitized solar cells assembled with aqueous electrolytes are emerging as a sustainable photovoltaic technology suitable for safe indoor and portable electronics use. While the scientific community is exploring unconventional materials for preparing electrodes and electrolytes, this work presents the first study on zinc oxide as a semiconductor material to fabricate photoanodes for aqueous solar cells. Different morphologies (i.e., nanoparticles, multipods, and desert roses) are synthesized, characterized, and tested in laboratory-scale prototypes. This exploratory work, also integrated by a computational study and a multivariate investigation on the factors that influence electrode sensitization, confirms the possibility of using zinc oxide in the field of aqueous photovoltaics and opens the way to new morphologies and processes of functionalization or surface activation to boost the overall cell efficiency.

Use of deep eutectic solvents in environmentally-friendly dye-sensitized solar cells and their physicochemical properties: a brief review

A novel way to mitigate the greenhouse effect is to use dye-sensitized solar cells (DSSCs) to convert carbon dioxide from the air into useful products, such as hydrocarbons, which can also store energy from the sun, a plentiful, clean, and safe resource. The conversion of CO2 can help reduce the impacts of greenhouse gas emissions that contribute to global warming. However, there is a major obstacle in using DSSCs, since many solar devices operate with organic electrolytes, producing pollutants including toxic substances. Therefore, a key research area is to find new eco-friendly electrolytes that can effectively dissolve carbon dioxide. One option is to use deep eutectic solvents (DESs), which are potential substitutes for ionic liquids (ILs) and have similar advantages, such as being customizable, economical, and environmentally friendly. DESs are composed of low-cost materials and have very low toxicity and high biodegradability, making them suitable for use as electrolytes in DSSCs, within the framework of green chemistry. The purpose of this brief review is to explore the existing knowledge about how CO2 dissolves in DESs and how these solvents can be used as electrolytes in solar devices, especially in DSSCs. The physical and chemical properties of the DESs are described, and areas are suggested where further research should be focused.

Stabilization of Perovskite Solar Cells: Recent Developments and Future Perspectives

Exceptional power conversion efficiency (PCE) of 25.7% in perovskite solar cells (PSCs) has been achieved, which is comparable with their traditional rivals (Si-based solar cells). However, commercialization-worthy efficiency and long-term stability remain a challenge. In this regard, there are increasing studies focusing on the interface engineering in PSC devices to overcome their poor technical readiness. Herein, the roles of electrode materials and interfaces in PSCs are discussed in terms of their PCEs and perovskite stability. All the current knowledge on the factors responsible for the rapid intrinsic and external degradation of PSCs is presented. Then, the roles of carbonaceous materials as substitutes for noble metals are focused on, along with the recent research progress in carbon-based PSCs. Furthermore, a sub-category of PSCs, that is, flexible PSCs, is considered as a type of exceptional power source due to their high power-to-weight ratios and figures of merit for next-generation wearable electronics. Last, the future perspectives and directions for research in PSCs are discussed, with an emphasis on their commercialization.

Deep Eutectic Solvents in Solar Energy Technologies

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.

Novel variations in spermatogenic transcription regulators RFX2 and TAF7 increase risk of azoospermia

PURPOSE

Genetic etiology of idiopathic male infertility is enigmatic owing to involvement of multiple gene regulatory networks in spermatogenesis process. Any change in optimal function of the transcription factors involved in this process owing to polymorphisms/mutations may increase the risk of infertility. We investigated polymorphisms/mutations of spermatogenic transcription regulators TAF7 and RFX2 and analysed their association with incidence of azoospermia among the men from West Bengal, India.

METHODS

Genotyping was carried by Sanger's dideoxy sequencing of 130 azoospermic men who were detected negative in Y chromosome microdeletion screening and 140 healthy controls. Association study was done by suitable statistical methods. In silico analysis was performed to infer the intuitive damaging effects of detected variants at transcripts and protein level.

RESULTS

We found significant association of TAF7 C16T (MW827584 G > A), RFX2 562delT (MZ560629delA), rs11547633 A > C, rs17606721 A > G, MW827583 C > T, and MZ379836 C > T variants with the incidence of azoospermia. In silico analysis predicted that the variants either alter the natural splice junctions of the transcript or cause probable damage in the structure of proteins of respective genes.

CONCLUSION

Polymorphisms/mutations of TAF7 and RFX2 genes increase risk of male infertility in Bengali population. The novel variants may be used as markers for male infertility screening in ART practise.

Lignin-Based Polymer Electrolyte Membranes for Sustainable Aqueous Dye-Sensitized Solar Cells

In the quest for sustainable materials for quasi-solid-state (QS) electrolytes in aqueous dye-sensitized solar cells (DSSCs), novel bioderived polymeric membranes were prepared in this work by reaction of preoxidized kraft lignin with poly(ethylene glycol)diglycidylether (PEGDGE). The effect of the PEGDGE/lignin relative proportions on the characteristics of the obtained membranes was thoroughly investigated, and clear structure-property correlations were highlighted. In particular, the glass transition temperature of the materials was found to decrease by increasing the amount of PEGDGE in the formulation, indicating that polyethylene glycol chains act as flexible segments that increase the molecular mobility of the three-dimensional polymeric network. Concurrently, their swelling ability in liquid electrolyte was found to increase with the concentration of PEGDGE, which was also shown to influence the ionic transport efficiency within the membrane. The incorporation of these lignin-based cross-linked systems as QS electrolyte frameworks in aqueous DSSCs allowed the preparation of devices with excellent long-term stability under UV-vis light, which were found to be superior to benchmark QS-DSSCs incorporating state-of-the-art carboxymethylcellulose membranes. This study provides the first demonstration of lignin-based QS electrolytes for stable aqueous DSSCs, establishing a straightforward strategy to exploit the potential of lignin as a functional polymer precursor for the field of sustainable photovoltaic devices.

Association study between single-nucleotide variants rs12097821, rs2477686, and rs10842262 and idiopathic male infertility risk in Serbian population with meta-analysis

PURPOSE

A genome-wide association study conducted in the Han Chinese population identified three single nucleotide variants rs12097821, rs2477686, and rs10842262 as being significantly associated with non-obstructive azoospermia. Our aim was to evaluate the possible association between these susceptibility loci and idiopathic male infertility risk in the Serbian population.

METHODS

A case-control study was conducted on 431 male individuals from the Serbian population divided into two groups. The case group consisted of 208 males diagnosed with oligoasthenozoospermia or non-obstructive azoospermia, while the control group involved 223 fertile men who have fathered at least one child.

RESULTS

According to codominant (P_codom = 0.048, OR_codom = 0.57, 95%CI 0.35-0.92) and overdominant (P_overdom = 0.017, OR_overdom = 0.62, 95%CI 0.42-0.92) genetic models, rs10842262 was found to be associated with male infertility. Stratifying infertile men according to diagnosis yielded statistically significant results for non-obstructive azoospermia cases under multiple genetic models (P_codom = 0.038, OR_codom = 0.47, 95%CI 0.26-0.85; P_dom = 0.031, OR_dom = 0.53, 95%CI 0.30-0.94; P_overdom = 0.016, OR_overdom = 0.55, 95%CI 0.33-0.90). Minor allele C of rs2477686 genetic variant was shown to be associated with the reduced risk of oligoasthenozoospermia under the log-additive genetic model (P = 0.03, OR = 0.69, 95%CI 0.50-0.97). The results of the meta-analysis indicate both rs2477686 and rs10842262 to be associated with male infertility.

CONCLUSION

Our results show variants rs2477686 and rs10842262 to be significantly associated with male infertility in the Serbian population. Nevertheless, case-control studies in other populations are needed to validate their association with infertility in males diagnosed with oligoasthenozoospermia and non-obstructive azoospermia.

Hydrogel Electrolytes Based on Xanthan Gum: Green Route towards Stable Dye-Sensitized Solar Cells

The investigation of innovative electrolytes based on nontoxic and nonflammable solvents is an up-to-date, intriguing challenge to push forward the environmental sustainability of dye-sensitized solar cells (DSSCs). Water is one of the best choices, thus 100% aqueous electrolytes are proposed in this work, which are gelled with xanthan gum. This well-known biosourced polymer matrix is able to form stable and easily processable hydrogel electrolytes based on the iodide/triiodide redox couple. An experimental strategy, also supported by the multivariate chemometric approach, is used here to study the main factors influencing DSSCs efficiency and stability, leading to an optimized system able to improve its efficiency by 20% even after a 1200 h aging test, and reaching an overall performance superior to 2.7%. In-depth photoelectrochemical investigation demonstrates that DSSCs performance based on hydrogel electrolytes depends on many factors (e.g., dipping conditions, redox mediator concentrations, etc.), that must be carefully quantified and correlated in order to optimize these hydrogels. Photovoltaic performances are also extremely reproducible and stable in an open cell filled in air atmosphere, noticeably without any vacuum treatments.

A water-based and metal-free dye solar cell exceeding 7% efficiency using a cationic poly(3,4-ethylenedioxythiophene) derivative

A green, efficient and stable solar cell based only on water and safe and cheap elements of the periodic table is proposed in this work, finally consolidating (also from a sustainability viewpoint) the concept of "artificial photosynthesis" studied for decades by the scientific community. The concept of dye-sensitized solar cells is re-proposed here with a metal-free organic dye, an iodine-based electrolyte in a 100% aqueous environment and a new cathode (cationic PEDOT) synthesized for the first time with the aim of inhibiting the repulsion between the anions of redox couples and the PEDOT:PSS matrix commonly used as the counter-electrode. This elegant setup leads to a record efficiency of 7.02%, the highest value ever obtained for a water-based solar cell and, in general, for a photovoltaic device free of both organic solvents and expensive/heavy metals.

Metal Coordination Complexes as Redox Mediators in Regenerative Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have attracted a substantial interest in the last 30 years for the conversion of solar power to electricity. An important component is the redox mediator effecting the transport of charge between the photoelectrode and the dark counter electrode (CE). Among the possible mediators, metal coordination complexes play a prominent role and at present are incorporated in several types of devices with a power conversion efficiency exceeding 10%. The present review, after a brief introduction to the operation of DSSCs, discusses at first the requirements for a successful mediator. Subsequently, the properties of various classes of inorganic coordination complexes functioning as mediators relevant to DSSC operation are presented and the operational characteristics of DSSC devices analyzed. Particular emphasis is paid to the two main classes of efficient redox mediators, the coordination complexes of cobalt and copper; however other less efficient but promising classes of mediators, notably complexes of iron, nickel, manganese and vanadium, are also presented.

Solar electricity and fuel production with perylene monoimide dye-sensitised TiO2 in water

Anchor-bearing perylene monoimide dyes were synthesised and studied back-to-back in both aqueous dye-sensitised solar cells and semiconductor photocatalysis.

Dye-sensitisation of TiO₂ and other metal oxides is an established strategy to couple solar light harvesting with efficient charge separation for the production of electricity in dye-sensitised solar cells (DSCs) or fuels in dye-sensitised semiconductor photocatalysis (DSP). Perylene monoimide (PMI) dyes have emerged as promising organic dyes, but they have not previously been used in a functional assembly with TiO₂ in aqueous solution. Here, five novel PMI dyes bearing carboxylic acid, phosphonic acid, acetylacetone, hydroxyquinoline or dipicolinic acid anchoring groups for attachment onto TiO₂ are reported. We identified functional DSC and DSP systems with PMI-sensitised TiO₂ in aqueous solution, which permitted a side-by-side comparison with respect to performance between the two systems. Structure–activity relationships allowed us to suggest anchor-condition-system associations to suit specific anchoring groups at various pH values, and with different electron mediators (redox couple or sacrificial electron donor) and catalysts in DSC and DSP schemes. A DSC sensitised with the hydroxyquinoline-modified PMI dye reached the highest short-circuit current density (J_SC ≈ 1.4 mA cm^–2) in aqueous electrolyte solution during irradiation with simulated solar light. This dye also achieved a turnover number (TON_PMI) of approximately 4900 for sacrificial proton reduction after 24 h irradiation in a DSP scheme with Pt as a H₂-evolving co-catalyst at pH 4.5. This performance was only surpassed by the carboxylic acid-bearing dye, which reached a new benchmark turnover number (TON_PMI ≈ 1.1 × 10⁴ after 72 h) for an organic dye in nanoparticulate DSP for solar fuel production. At higher pH (8.5), our results showed that the phosphonic acid group allows for higher performance due to a stronger anchoring ability. This study provides a platform for aqueous PMI dye-sensitised TiO₂ chemistry and gives valuable insights into the performance of different anchoring groups in DSC and DSP systems.

Synthesis and Characterization of Novel β-Bis( N, N-diarylamino)-Substituted Porphyrin for Dye-Sensitized Solar Cells under 1 sun and Dim Light Conditions

In this work, we have synthesized a novel porphyrin dye named SK7, which contains two N, N-diarylamino moieties at two β-positions as electron-donating units and one carboxy phenylethynyl moiety at the meso-position as an electron-withdrawing, anchoring group. This novel dye was tested for the application in dye-sensitized solar cells. The light-harvesting behavior of SK7 and YD2 was investigated using UV-vis absorption and density functional calculation. The electron transport properties at the TiO₂/dye/electrolyte interface for SK7- and YD2-based devices were evaluated by electrochemical impedance spectroscopy. X-ray crystallographic characterization was conducted to understand the influence of two N, N-diarylamino units at two β-positions. The power conversion efficiencies of ca. 6.54% under 1 sun illumination (AM 1.5G) and ca. 19.72% under a T5 light source were noted for the SK7 dye. The performance of SK7 is comparable to that of dye YD2, which contains only one N, N-diarylamino moiety at the meso-position (ca. 7.78 and 20.00% under 1 sun and T5 light, respectively).

Stable Radical Materials for Energy Applications

Although less studied than their closed-shell counterparts, materials containing stable open-shell chemistries have played a key role in many energy storage and energy conversion devices. In particular, the oxidation-reduction (redox) properties of these stable radicals have made them a substantial contributor to the progress of organic batteries. Moreover, the use of radical-based materials in photovoltaic devices and thermoelectric systems has allowed for these emerging molecules to have impacts in the energy conversion realm. Additionally, the unique doublet states of radical-based materials provide access to otherwise inaccessible spin states in optoelectronic devices, offering many new opportunities for efficient usage of energy in light-emitting devices. Here, we review the current state of the art regarding the molecular design, synthesis, and application of stable radicals in these energy-related applications. Finally, we point to fundamental and applied arenas of future promise for these designer open-shell molecules, which have only just begun to be evaluated in full.