Solar Light Absorption Research Articles

A new synthesis route of Bi2S3 with solvothermal deposition in photoelectrochemical hydrogen production

Bi2S3 semiconductor is widely preferred in photocatalytic applications due to its absorption in the visible region and near-infrared regions. In this paper, Bi2S3 is synthesized with a novel S2− source including thiosalicylic acid and 2-thiouracil compounds containing by only a one-step solvothermal method at different pHs (1, 2 and 3 called S_pH1, S_pH2 and S_pH3), apply KCl agent to enhanced surface homogeneity to the most catalytic deposition bath (S_K_pH1) and examine surface morphology, crystal structure, solar light absorption and photoelectrochemical hydrogen production performance. FESEM images show that Bi2S3 nanosphere structures are formed and that changing the pH of the deposition bath and the addition of a KCl surface agent changed the homogeneity of the size of the nanosphere structures. The photoelectrochemical performance test indicates that S_K_pH1 photoanode performs the highest catalytic photocurrent density of 2.28 mA cm−2 (vs. 1.23 V RHE) followed by S_pH1 (1.86 mA cm−2), S_pH2 (1.74 mA cm−2) and S_pH3 (1.40 mA cm−2) in LSV measurement. Mott-Schottky results show Bi2S3 electrodes as a n-type semiconductor and Vfb of S_K_pH1 is the most negative, enabling improved photocatalytic performance. EIS measurement shows that decreasing pH of the deposition bath and KCl addition provide reducing Rct (faradaic process) and Rp with applied 1.23 V (vs. NHE) under 100 mW cm−2.

Dual‐Plasmonic Ti3C2Tx/CuSe 2D/2D Solar Absorber and a Hydrophilic Device for Efficient Solar‐Driven Water Collection

Solar water evaporation is an emerging technology for drinkable water generation, while it remains a challenge to develop materials and device for efficient water evaporation and collection. Herein, dual‐plasmonic Ti3C2Tx/CuSe two‐dimensional (2D)/2D hybrids are prepared for high‐efficiency solar water evaporation and a hydrophilic device is designed for efficient water collection. The Ti3C2Tx/CuSe hybrids, which monocrystalline CuSe ultrathin nanosheets are chemically bonded with Ti3C2Tx nanosheets, show efficient photothermal conversion owing to the plasmon‐coupling‐induced strong light absorption and fast charge transfer in the 2D/2D interface. By transferring the hybrids on a cotton piece, the Ti3C2Tx/CuSe membrane displays over 95% of solar light absorption, a stable evaporation rate of 1.893 kg m−2 h−1, and solar‐to‐vapor efficiency of 99.13% under one‐sun irradiation. The membrane can also treat water with more than 20 wt% salinity due to the rich microchannel for ion diffusion. Furthermore, a water evaporation device, which the cambered roof is painted with hydrophilic SiO2, is designed for efficient water collection. The treated roof can efficiently reduce the optical loss and transfer the vapor condensation, leading to a high average freshwater generation of 16.4 kg m−2 in a daily (10 h) natural light irradiation, much higher than other reported devices.

Mid-Infrared (MIR) Complex Refractive Index Spectra of Polycrystalline Copper-Nitride Films by IR-VASE Ellipsometry and Their FIB-SEM Porosity

Copper-nitride (Cu3N) semiconductor material is attracting much attention as a potential, next-generation thin-film solar light absorber in solar cells. In this communication, polycrystalline covalent Cu3N thin films were prepared using reactive-RF-magnetron-sputtering deposition, at room temperature, onto glass and silicon substrates. The very-broadband optical properties of the Cu3N thin film layers were studied by UV-MIR (0.2–40 μm) ellipsometry and optical transmission, to be able to achieve the goal of a low-cost absorber material to replace the conventional silicon. The reactive-RF-sputtered Cu3N films were also investigated by focused ion beam scanning electron microscopy and both FTIR and Raman spectroscopies. The less dense layer was found to have a value of the static refractive index of 2.304, and the denser film had a value of 2.496. The iso-absorption gap, E04, varied between approximately 1.3 and 1.8 eV and could be considered suitable as a solar light absorber.

MoSe2 and WSSe heterojunction with exceptional power conversion efficiency and photogalvanic effect

In this paper, the structure, electronic and optical properties of WSSe/MoSe2 and MoSe2/WSSe heterojunctions are studied by using density functional theory (DFT) and first principles. We find that WSSe/MoSe2 has high electron mobility (1131 cm2/Vs) and strong solar light absorption. It is worth noting that both WSSe/MoSe2 (17.0 %) and MoSe2/WSSe (14.3 %) have excellent power conversion efficiency (PCE), and the PCE of WSSe/MoSe2 is as high as 22.7 % through biaxial strain control, which can realize efficient optical energy conversion of optoelectronic devices. More interestingly, we have built the armchair WSSe/MoSe2 and MoSe2/WSSe self-powered optoelectronic detectors. Under the irradiation of linearly polarized light (LPL) and circularly polarized light (CPL), it is found that the photogalvanic effect photocurrent (Iph) will change sensitively with the polarization angle θ and photon energy, and the larger Iph be produced. This enhancement is of great significance to the design and development of self-powered optoelectronic detector.

Perfect Solar Light Absorption and Efficient Photo-Thermal Generation

Perfect Solar Light Absorption and Efficient Photo-Thermal Generation

A facile reflux method to produce ternary CQDs/P25/NH2−MIL-125 for photocatalytic degradation of methylene blue under simulated solar light

BackgroundTo enhance the photocatalytic performance of commercial titanium dioxide (P25), carbon quantum dots (CQDs) and NH2−MIL-125 were utilized to address its limitations arising from the large bandgap and small specific surface area. The CQDs were employed to broaden the range of solar light absorption, while NH2−MIL-125 was used to disperse P25 with a higher specific surface area. MethodsA facile reflux method was conducted to synthesize CQD/P25/NH2−MIL-125 composite materials. The up-conversion photoluminescence (UCPL) effect of CODs was leveraged to convert longer wavelengths of light into shorter ones, facilitating P25 and NH2−MIL-125 to enhance photocatalytic performance. Significant findingsThe UCPL effect of CQDs not only broadened the light absorption range but also retarded the recombination of photo-induced electron-hole pairs, leading to improved photocatalytic reactions. Furthermore, the effect of additional amounts of CQDs was investigated, and it was found that 1wt% CQDs/P25/NH2−MIL-125 followed first-order kinetics, with the highest rate constant (k1) of 0.0141.

Direct laser printing of 3D optical imaging based on full-spectrum solar-absorption-enhanced perovskite-type oxides

The exploration of the solar light absorption by a material is of great use in photonics and optoelectronics. However, the fully exploiting of the solar spectrum of well-known wide-bandgap perovskite oxides (2.7–5 eV), remains very challenging. We show that the selective occupation of Bi3+ in the octahedrally coordinated Ba2+ is responsible for creating sub-bandgap states (as low as 0.6 eV), nearly 9 times lower than pristine bandgap (5.2 eV). We reveal that the role of the 6s6p excited state of Bi3+ is as a bridge to promote the dipole-allowed band-band transition for strong absorption. Furthermore, we demonstrate the double-sided laser printing of three-dimensional optical imaging based on the photothermal effect, enabling write-once-read-many information storage with ultrahigh stability and good data retention. Our results make Ba3–xGa2O6:xBi3+ a promising candidate for photovoltaics, ferroelectrics, photocatalysis, broadband photodetectors as well as other photonic and optoelectronic applications.

Polypyrrole-modified natural eggplant aerogel with high shape recovery for simultaneous efficient clean water generation and heavy metal ion adsorption from wastewater

Solar water evaporation has proven to be one of the most effective approaches to generate clean water. However, simultaneous clean water generation and heavy metal ion removal is challenging and urgent for the treatment of wastewater containing heavy metal ions. Herein, polypyrrole (PPy)-modified natural eggplant (PPy@eggplant) aerogel was developed to effectively address the aforementioned problems. The resultant PPy@eggplant aerogel possessed impressive shape recovery capacity after absorbing water regardless of multiple squeezing and twisting, which contributed to usage stability in long-term applications. Moreover, the PPy@eggplant aerogel achieved solar light absorption of 98.48 % due to PPy uniform distribution and multiple light diffraction/scattering in the porous structure (porosity of 92.16 %), excellent water replenishment capacity (water droplet fully spread within 118 ms), and extremely low thermal conductivity (0.039 W·m−1·K−1). Thus, the PPy@eggplant aerogel demonstrated a high evaporation rate of 2.05 kg·m−2·h−1 and a simultaneous Cr6+ adsorption capacity of 27.83 mg·g−1 for treating dye water with Cr6+ ions. Additionally, the PPy@eggplant aerogel preserved the evaporation rate after a 10-h test, indicating long-term stability in practical applications. In conclusion, the impressive shape recovery capacity, high evaporation performance, and satisfactory Cr6+ adsorption ability make the PPy@eggplant aerogel a good alternative for treating wastewater, especially wastewater with heavy metal ions.

Architecture design of TiO2 with Co-doped CdS quantum dots photoelectrode for water splitting.

Photoelectrochemical hydrogen production is a critical key to solving the carbon-zero goal of countries due to renewable sources of solar light and combustion products of hydrogen-only water. Here, an architecture design for an n-type nano rosettes-rod TiO2 (RT) surface using CdS and Co-doped CdS quantum dots (QDs) is carried out utilizing the SILAR (simple ionic layer adsorption and reaction) method. Furthermore, the photocatalytic behaviour of Co-doped CdS QDs SILAR cycles deposition is investigated in various cycles, including 5, 8, 10, and 12. The FESEM, Raman XRD, Uv-Vis spectrometer, and vibration modes are used to evaluate the photoelectrode surface structure, crystal structure, and solar light absorption, respectively. FESEM images and XRD pattern revealed successive CdS QDS and Co-doped CdS QDs deposition on the RT boundary and rising SILAR cycles of Co-doped CdS QDs lead to further coverage of RT surface. UV-vis spectrometer indicated shifting solar light absorption to the visible region by applying more SILAR cycles of Co-doped CdS QDs deposition. The electrochemical parameters obtained from EIS showed total polarization resistance (Rp) of the RT electrode dramatically decreased with 10 SILAR cycle Co-doped CdS QDs deposition (5093 Ω cm2 and 617 Ω cm2). Linear sweep voltammetry (LSV) and chronoamperometric photocatalytic performance measurements indicated Co-doped CdS QDs on RT extremely enhanced photoresponse under solar irradiation and 10 SILAR cycle Co-doped CdS QDs improved photocurrent density about fourfold according to blank RT electrode.

Reduced TiO2 nanotube arrays as environmental catalysts that enable advanced oxidation processes: A mini review

Advanced oxidation processes (AOPs) that utilize heterogeneous catalysts are an engaging and compelling technology for treating emerging contaminants in water and wastewater. Substantial efforts have been devoted to developing cost-effective and environmentally benign materials for application in AOPs. Reduced TiO2 nanotube arrays (r-TNAs) have recently emerged as promising environmental materials for efficiently mitigating persistent organic pollutants (POPs) resistant to conventional biological treatment. r-TNAs possess distinct electrical, optical, and catalytic features, including superior conductivity and solar light absorption due to structural defects involving oxygen vacancies and Ti3+ states. Moreover, their well-organized open channel structures provide a substantial surface area, facilitating the efficient mass transfer of reactants and products. Notably, r-TNAs can be grown directly on the substrate without using organic adhesives or binders, which improves their mechanical and chemical durability and facilitates their repeated use. This article represents the pioneering comprehensive review of r-TNAs in AOP applications. We introduce an electrochemical anodization technique to fabricate TNAs and summarizes the reduction methods employed in r-TNA synthesis. We also elucidate the appealing attributes of r-TNAs and explore their applications in emerging AOPs, including persulfate activation, electrocatalysis, and photo(electro)catalysis. Finally, we outline critical challenges and provide insights into future prospects for the development of AOP systems based on r-TNAs.

Unleashing the power of sunlight: Bi2O3/Sb2S3 photocatalysis for sustainable wastewater remediation of Tetracycline and Rhodamine-B

The use of heterojunction photocatalysts for pollutant decomposition has garnered significant interest in mitigating water contamination and environmental pollution. Our present study focuses on synthesizing Bi2O3/Sb2S3 heterojunction photocatalyst having variable mole ratios by employing a hydrothermal technique. Loading Sb2S3 onto Bi2O3 enables broad-spectrum solar light absorption, efficient segregation of charges, and enhanced surface area, which are excellent traits for photocatalysis. Both Bi2O3 and Sb2S3 showed nano-rod type morphology, while Sb2S3 was present as smaller nano-rods and Bi2O3 as larger ones. The photocatalytic performance of this heterojunction photocatalyst was examined using Rhodamine-B (RhB) and Tetracycline (TC) under solar light illumination for 120 min. Remarkable decomposition efficiency was achieved, with a 98.2% degradation rate observed for RhB having a rate constant of 0.03149 min−1. Similar experiments were conducted using other light sources as well, such as visible light and UV light. However, only 83% and 69% RhB degradation rates were attained with visible and UV light, respectively, indicating that natural sunlight is the superior light source for our catalyst. A 91.5% degradation rate was achieved for TC with the rate constant of 0.01749 min−1, in the presence of sunlight for 120 min. A small amount (0.3 g/L) of 1:3 Bi2O3/Sb2S3 (13BOSBS) photocatalyst was enough to bring such a good result. The photocatalytic activity of our catalyst, that is, 98.2% RhB degradation, is much higher than that of commercially available TiO2–P25 powder, as the latter only achieved 52% RhB degradation. The pH at which the surface of Bi2O3/Sb2S3 has a zero charge (pHpzc) was determined to be 5.37 and the maximum decomposition of RhB was achieved at pH 7. Reusability tests verified the remarkable stability of this catalyst, with about 74.4% of RhB degradation still present after seven consecutive cycles. Scavenger experiments highlighted the crucial role of •OH radicals in the photodecomposition mechanism, as the incorporation of DMSO significantly influenced the photocatalytic efficiency of the 13BOSBS composite, leading to a notable decrease to 37.5% in RhB degradation. For the RhB dye, the 13BOSBS catalyst demonstrated remarkable 90.2% and 85% reductions in COD and TOC, respectively. The commercially available TC powder substantially reduced 84% in COD and 80% in TOC, whereas there was a 78% reduction in COD and 73% in TOC for TC tablets. The degradation of the contaminants was followed by the formation of simpler intermediates, which were discovered using the GC-MS approach. Owing to its excellent attributes and simple synthesis method, the fabricated heterojunction offers a promising solution to prevent the persistent buildup of harmful toxic pollutants in industrial wastewater systems.

Designing g-C3N4/ZnCo2O4 nanocoposite as a promising photocatalyst for photodegradation of MB under visible-light excitation: Response surface methodology (RSM) optimization and modeling

Creating a Z-scheme heterojunction system can enhance the efficiency of separating and transporting charge carriers responsible for degrading pollutants. Hence, in this study, ZnCo2O4 was combined with g-C3N4 through a straightforward approach to create a novel Z-scheme heterogeneous nanocomposite. Various techniques were employed to inspect the photocatalysts' crystallinity, morphology, chemical composition, functional groups, band structure, and electrochemical properties. The Photocatalytic degradation of methylene blue reveals that the catalytic activity of g-C3N4/ZnCo2O4 nanocomposite (414 × 10−4 min−1) is considerably greater than that of the individual building units (g-C3N4: 45.7 × 10−4 min−1 and ZnCo2O4 79.5 × 10−4 min−1). The impact of operational parameters such as photocatalyst dosage (mg), pH, and dye concentration (ppm) on the photodegradation ability of the nanocomposite g-C3N4/ZnCo2O4 was assessed and optimized based on response surface methodology and central composite design model. The highest level of degradation, reaching 99%, was gained in the optimal condition, including pH = 7, 90 mg of g-C3N4/ZnCo2O4 photocatalyst, and 5 ppm of MB. The photoluminescence and electrochemical impedance spectroscopy results revealed that the significant attenuation of the generated electron-hole pair recombination increased the nanocomposite photocatalytic performance. Also, extensive solar light absorption and adaptation of the band structures of the two semiconductors resulted in increased photocatalytic activity. The addition of scavengers to the photocatalytic test environment showed the importance of the contribution of each active species in the decomposition of methylene blue. The heterojunction photocatalytic system showed good reproducibility and reusability in the reaction solution.

Hierarchically ordered microporous Ag2S QDs-CoOx/NC nanostructures for enhancing photocatalytic CO2 reduction to chemical fuels

Rational design of advanced architectural photocatalysts with efficient separation and transfer of photoinduced charge carriers, and well solar light absorption ability is of critical significance for solar energy utilization and CO2-to-fuel conversion. Herein, a novel three-dimensional (3D) ordered hollow-wall hybrid composite (3DOM Ag2S-CoOx/NC) has been developed by integrating ultrafine Ag2S quantum dots (QDs) on the surface of metal–organic frameworks (MOFs)-derived hierarchically ordered macroporous nitrogen-doped carbon skeletons with implanted CoOx nanoclusters (3DOM CoOx/NC). Compared with pristine 3DOM CoOx/NC and traditional ZIF-67-derived CoOx/NC, the constructed 3DOM Ag2S-CoOx/NC composite exhibits remarkable performances toward the photocatalytic conversion of CO2 and H2O vapor without any sacrifice reagents to fuels (CO-66.00 μmol g−1h−1, CH4-1.21 μmol g−1h−1 and C2H4-2.33 μmol g−1h−1) and a higher C2H4 selectivity (16.47%) in the gas–solid system under light irradiation (λ > 420 nm). Impressively, dual Z-scheme charge transfer pathways in the 3DOM Ag2S-CoOx/NC can provide good channels for boosting electron transfer and charge separation. Experimental characterizations combined with density functional theory (DFT) calculations further elucidate that the key role of Ag2S QDs is served as an auxiliary in the 3DOM Ag2S-CoOx/NC catalyst to improve the electronic structure and further facilitate adsorption/activation capacity of CO2 and H2O. Moreover, the multiple photocatalytic mechanisms including related key intermediates and conversion process of CO2 molecules are further identified by in-situ diffuse reflectance infrared fourier transform spectra (DRIFTS). This innovation provides a novel strategy to design well-designed hierarchically porous hybrid structures for photocatalytic CO2 reduction to high-value fuels.

Three-dimensional disposable wooden chopsticks-derived solar-thermal evaporators for environmental energy-enhanced water evaporation and purification

Although solar steam generation is a sustainable and promising approach for generating clean water by purifying wastewater and desalinating seawater, its solar energy utilization efficiency and solar steam generation performance have to be improved further. Environmental energy-enhanced three-dimensional (3D) solar-thermal water evaporators are fabricated by decorating hydrophilic and porous disposable wooden chopsticks with black solar-thermal carbon nanotubes (CNTs) followed by assembling the CNT-decorated wooden chopsticks into a 3D array for efficient water evaporation and purification. The breaking of a chopstick creates 3D jagged fracture surface, increasing solar light absorption, enlarging evaporation area, and improving the water evaporation performance under downward solar light irradiation. The large sidewall of the chopsticks harvests environmental energy to accelerate water evaporation via thermal convection and radiation driven by the temperature gradient during the solar steam generation process. The CNT-decorated disposable chopstick evaporator with an exposed height of 4 cm achieves a remarkable evaporation rate of 3.70 kg m−2 h−1 and a high energy efficiency of 122.2 % under 1-sun irradiation, exhibiting application prospects in seawater desalination and wastewater purification.

Peak-like three-dimensional CoFe2O4/carbon nanotube decorated bamboo fabrics for simultaneous solar-thermal evaporation of water and photocatalytic degradation of bisphenol A

Catalytic CoFe2O4 and solar-thermal carbon nanotube decorated bamboo fabrics (CCBF) are fabricated for integrating efficient solar steam generation from wastewater with catalytic degradation of its organic contaminants. Thanks to the numerous porous channels and polar groups of bamboo fabric and the efficient solar-thermal energy conversion of black carbon nanotubes, the porous and hydrophilic CCBF exhibits fast upward transport of water, efficient solar light absorption, and high solar-thermal energy conversion efficiency. The decorated CoFe2O4 not only enhances the solar-thermal energy conversion efficiency of CCBF but also activates potassium peroxymonosulfate to generate abundant highly active species for catalytic degradation of bisphenol A (BPA). Furthermore, folding the CCBF into a peak-like 3D evaporator can enhance solar energy utilization, and gain environmental energy for promoting solar-thermal water evaporation and catalytic degradation performances. The 3D CCBF evaporator achieves a water evaporation rate of 2.72 kg m–2 h–1 under 1-sun irradiation. Meanwhile, 100% of the BPA in the seawater can be degraded within 10 min. An exceptional high purification efficiency of 27.72 kg m–2 h–1 is achieved with the 3D evaporator during a long-term treatment of BPA-containing seawater under 1-sun irradiation. This work demonstrates efficient purification of seawater/wastewater with both metal ions and organic pollutants by simultaneous solar-thermal evaporation of water and catalytic degradation of organic pollutants.

Design and large-scale nanofabrication of plasmonic solar light absorbers

Surface plasmon resonances have been exploited for many applications due to their tunability, which is directly related to the geometry of nanostructures. Based on their dimension and material stack, the resonances can be tailored to achieve high absorbing or reflecting nanopatterned surfaces designed for specific wavelengths. While the preferred lithographic printing techniques in the field allow high precision and control of the structures, they are limited in throughput, thus restricting possible large-scale applications. In this work, we present a full process flow, which can produce hundreds of square meters of nanopillar arrays by combining resolution enhancement techniques (RETs) on a deep-UV stepper for fabricating a silicon master and roll-to-roll extrusion coating (R2R-EC) for its replication. We demonstrate optimized exposures with the combination of dipole off-axis illumination, triple cross-exposure, and the addition of assisted features on the mask design. By simulating the RETs compared to a conventional setup, we show how lithographic parameters such as the normalized image log-slope (NILS) improve from 0.90 to 2.05 or the resist image contrast (RIC) increases from 0.429 to 0.813. We confirm these results by printing wafer-size hexagonal and rectangular arrays of nanopillars with 340, 350, and 360 nm pitches and diameters ranging from 100 to 200 nm. We show the successful replication of both designs by R2R-EC, an industrial process, which produces hundred-meter rolls of patterned polymer. We demonstrate that after metallization, the samples are suitable for solar absorption by measuring their absorptance (absorbed to incident intensity) and comparing it with the solar irradiance peak. We achieve a 70% efficiency for both hexagonal and rectangular arrays at resonant peaks of 550 and 600 nm, respectively, where the hexagonal array better matches the solar irradiance peak. Additionally, the plasmonic samples block 78% of the heat radiation when compared to a plain black polymer foil for reference, making them more efficient for solar harvesting applications.

A Review on Pulsed Laser Fabrication of Nanomaterials in Liquids for (Photo)catalytic Degradation of Organic Pollutants in the Water System.

The water pollution caused by the release of organic pollutants has attracted remarkable attention, and solutions for wastewater treatment are being developed. In particular, the photocatalytic removal of organic pollutants in water systems is a promising strategy to realize the self-cleaning of ecosystems under solar light irradiation. However, at present the semiconductor-based nanocatalysts can barely satisfy the industrial requirements because their wide bandgaps restrict the effective absorption of solar light, which needs an energy band modification to boost the visible light harvesting via surface engineering. As an innovative approach, pulsed laser heating in liquids has been utilized to fabricate the nanomaterials in catalysis; it demonstrates multi-controllable features, such as size, morphology, crystal structure, and even optical or electrical properties, with which photocatalytic performances can be precisely optimized. In this review, focusing on the powerful heating effect of pulsed laser irradiation in liquids, the functional nanomaterials fabricated by laser technology and their applications in the catalytic degradation of various organic pollutants are summarized. This review not only highlights the innovative works of pulsed laser-prepared nanomaterials for organic pollutant removal in water systems, such as the photocatalytic degradation of organic dyes and the catalytic reduction of toxic nitrophenol and nitrobenzene, it also critically discusses the specific challenges and outlooks of this field, including the weakness of the produced yields and the relevant automatic strategies for massive production.

Enhanced Solar Light-Driven Photocatalytic Degradation of Tetracycline Using Fe3+-Doped CdO/ZnS Nanocomposite: Mechanistic Insights and Performance Evaluation

In recent years, studies on the efficient spatial charge separation for broad solar light absorption and water remediation have been a major priority. Moreover, the development of transition metal-doped nanocomposites for this purpose is a new endeavor in current research. Here, we constructed an Fe3+-doped CdO/ZnS nanocomposite with a low doping level and investigated the effect of doping on the charge transfer and recombination behavior for improved photocatalytic performance. The X-ray diffraction analysis results indicate that both materials, CdO and ZnS, exhibit a cubic phase structure with an average crystallite size of 35 nm. Morphology analysis of the Fe3+-doped CdO/ZnS nanocomposite confirms the formation of irregularly shaped particle-like structures. From the optical studies, the bandgap energies of CdO/ZnS and Fe3+-doped CdO/ZnS nanocomposites are 3.19 eV and 2.87 eV, respectively, which proved that the iron ions doping reduced the bandgap energy and extended the absorption to the visible range. The efficiency of photodegradation in the tested samples was evaluated using tetracycline under solar light exposure. The experimental results demonstrated that the Fe3+-doped CdO/ZnS nanocomposite outperformed the other samples, exhibiting a significantly higher photocatalytic activity. After 80 min, it achieved a remarkable degradation rate of 97.06%. The Fe3+-doped CdO/ZnS nanocomposite demonstrated good stability and recyclability after five cycles. Radical trapping experiments showed that hydroxyl (•OH) radicals play a key role in photodegradation.

Graphene Quantum Dots for Photocatalytic CO2 Reduction

Sustainable solar fuels production through reduction of molecular CO2 using photocatalysts is an eco‐friendly and dependable source of energy for the future and for controlling the global warming. The growth of quantum dots, especially, graphene quantum dots (GQD), has emerged as a flat 0D material offering unique properties like enhanced solar light absorption, surface reactivity, charge separation, and migration efficiency, which are invariably systemizing high solar photocatalytic CO2 reduction efficiency. In this review, the insights of thermodynamics and kinetics of CO2 reduction are discussed, followed by detailed encapsulation of modification strategies of GQDs and intrinsic analysis of CO2 reduction utilizing solar light. Progressively, the challenges and futuristic outlook of GQDs‐based photocatalytic systems for solar fuels production is also presented.

A Review on the Applicability of Luminescent Phosphors and Effective Positioning in Dye‐Sensitized Solar Cells for Enhanced Performance and Stability

The narrow range of solar light absorption facilitated by the photoactive organic dyes has been restricting the significant development, and large‐scale applications of dye‐sensitized solar cells (DSSC). The major problem that limits the power conversion efficiency (PCE) of DSSC is the limitations of the organic dyes (light absorbers in DSSC) to absorb beyond the visible region of solar spectrum that resulting in lower PCE (≈13%) as compared with the commercialized technologies. Hence, the focus on developing efficient strategies to harvest the ultraviolet and infrared light regions of the solar spectrum and effective conversion into the absorption limit of dyes and thereby increasing the device performance and stability is the emerging technological development in DSSCs. Rare earth ion‐doped upconversion (UC) and downconversion (DC) phosphors are the most promising solutions for the prevalent issues of the liquid junction solar cells. This review will focus on the emerging strategies for the PCE enhancement of DSSC with UC and DC materials. An exclusive review on the facile approach of simultaneous usage of both the UC and DC phosphors and the effective positioning of these spectral conversion phosphors, to achieve highly stable DSSCs with superior PCE is provided.