Preparation of high-yield CTS NSs through the hot injection method with the new blend of two ligands, oleic acid (OLA) and oleyl alcohol (OLAL) has been highlighted. The CTS NSs were treated with a ligand exchange process and analysed with various characterization methods. The cubic crystal structure of CTS NSs was confirmed with XRD results. This was not altered for ligand exchange treated samples. UV-Visible spectroscopic studies revealed good optical absorbance and the bandgap was estimated to be 1.63 eV. The presence of functional groups of OLAL and OLA was identified through infrared spectroscopy. The presence of mixed structures of nanorods and nanospheres was confirmed through SEM and TEM analyses. Significant changes appeared in optical and morphological results for ligand-exchanged samples. Among all ligand exchange treated samples, sodium sulfide-methanol (NS-MeOH) treated CTS NSs emerged as the best material for catalytic applications and the plausible growth mechanism of CTS nanorods was proposed.

Novel binary solvent mixtures of chlorinated carbon compounds (CCs = CCl4, CHCl3, and C2Cl4) and 1-octanol are used to prepare pastes of TiO2 nanoparticles (NPs), which facilitate the formation of stable and thick TiO2 mesoporous films for photoanodes of dye-sensitized solar cells (DSSCs). CCs and 1-octanol readily form a complex, leading to enhanced interparticle connectivity within TiO2 NPs through hydrogen bonding interactions. The as-prepared chemically sintered TiO2 films exhibit high porosity and homogeneity, and a strong interparticle network for improved mechanical stability. The highest power conversion efficiency (PCE) of 7.0 and 5.8% is achieved using C2Cl4 for fluorine-doped tin oxide (FTO)-based rigid-type DSSCs and flexible-photoanode (indium-doped tin oxide (ITO)-coated polyethylene naphthalate (ITO/PEN))-based DSSCs, respectively, under 1-sun illumination conditions. Furthermore, the optimized device exhibits a significantly high PCE of 19.9% under indoor low-intensity light conditions. Novel binary solvent mixtures of chlorinated carbon compounds (CCs = CCl4, CHCl3, and C2Cl4) and 1-octanol are used to prepare pastes of TiO2 nanoparticles (NPs), facilitating the formation of TiO2 mesoporous films for flexible photoanodes.

The hybrid-type of supercapacitors based on transition metal sulfides-carbon composite electrodes are found to be a prominent and emerging technological advancement with beneficial characteristics such as a larger surface area, high durability, and a unique charge storage mechanism. In this work, phase pure copper tin sulfide (Cu2SnS3/CTS) nanoparticles (NPs) and the nanocomposite of CTS NPs decorated graphitic carbon nitride (gC3N4) CTS-gCN were prepared by an inexpensive solvothermal approach. The CTS-gCN nanocomposite-based supercapacitors show a high specific capacitance of 477 F/g at 1 A g- 1 current density, which is much higher than the pristine CTS NPs based supercapacitors (362 F/g) in three electrode configurations. The asymmetric hybrid supercapacitors were prepared with CTS-gCN electrodes and reduced graphene oxide (rGO) as a negative electrode with potassium hydroxide (KOH) as an electrolyte. The electrochemical characteristics of asymmetric CTS-gCN//rGO supercapacitors exhibit battery-like behavior with a specific capacitance of 108 F/g at the scan rate of 1 A g- 1 with a high energy density of 42 W h kg- 1 and a power density of 835.4 W kg- 1. The CTS-gCN// rGO supercapacitors show excellent capacitance retention over 94 % even after 2000 cycles. The obtained electrochemical results of the supercapacitors with high energy density, power density, wider potential window, and cyclic stability suggest the CTS-gCN//rGO hybrid supercapacitors as a promising candidate for emerging electrochemical energy storage technologies.

The hydrogen evolution reaction (HER) driven by electrocatalytic water splitting is attaining prevalent attention for the manufacturing of clean and green hydrogen energy. Herein, we report the simple one-step hydrothermal synthesis of cobalt sulfide nanoflakes decorated with reduced graphene oxide (CoS/rGO) nanocomposites as an effective electrode material for HER. The CoS/rGO nanocomposites exhibited the rGO nanosheet-decorated hierarchically interconnected CoS nanoflakes structure. The CoS/rGO nanocomposites exhibited an excellent HER activity with a low overpotential of 371 mV and a small Tafel slope of 103 mV/dec. More interestingly, the catalytic stability of CoS/rGO nanocomposites is comparatively higher than the pristine CoS NFs. These results suggest that the facile nanocomposites of CoS/rGO could be a prominent catalytic material for effective green hydrogen production.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Wide-bandgap perovskite solar cells (PSCs) with high open-circuit voltage (V-oc) represent a compelling and emerging technological advancement in high-performing perovskite-based tandem solar cells. Interfacial engineering is an effective strategy to enhance V-oc in PSCs by tailoring the energy level alignments between the constituent layers. Herein, n-type quinoxaline-phosphine oxide-based small molecules with strong dipole moments is designed and introduce them as effective cathode interfacial layers. Their strong dipole effect leads to appropriate energy level alignment by tuning the work function of the Ag electrode to form an ohmic contact and enhance the built-in potential within the device, thereby improving charge-carrier transport and mitigating charge recombination. The organic interfacial layer-modified wide-bandgap PSCs exhibit a high V-oc of 1.31 V (deficit of <0.44 V) and a power conversion efficiency (PCE) of 20.3%, significantly improved from the device without an interface dipole layer (V-oc of 1.26 V and PCE of 16.7%). Furthermore, the hydrophobic characteristics of the small molecules contribute to improved device stability, retaining 95% of the initial PCE after 500 h in ambient air.

Interfacial engineering in organic-inorganic hybrid perovskite solar cells (PSCs) has attracted significant attention, aiming to achieve high-performing and highly stable devices. Here, newly designed organic small molecules based on quinoxaline and triphenylamine for inverted type wide-bandgap PSCs are introduced, with the objective of enhancing the interfacial properties between perovskite and NiOx hole transport layer (HTL). The incorporation of an organic interlayer effectively reduces the energy level offset between the HTL and wide-bandgap perovskite, while passivating defects within the perovskite layer. It leads to improved charge extraction and minimized non-radiative recombination at the interface. Furthermore, the enhanced interfacial characteristics and hydrophobicity contribute to the improvement of perovskite film quality, resulting in larger grain size and higher crystallinity. As a result, the power conversion efficiency (PCE) of the PSC is enhanced from 18.9% to 20.1% with the incorporation of the IQTPAFlu interlayer, accompanied by an increase in Voc to approximate to 1.3 V, achieving a significantly low Voc deficit of 0.46 V. And the IQTPAFlu-based devices demonstrate stable and consistent performance over 500 h, with approximate to 91% of their initial PCE retained. The highly stable wide-bandgap PSCs, characterized by high Voc and PCEs, hold great promise as potential candidates for tandem solar cells. Quinoxaline and triphenylamine-based organic small molecules are designed to enhance the interfacial properties between the perovskite and the NiOx hole transport layer in inverted-type wide-bandgap perovskite solar cells (PSCs). The integration of these organic interlayers effectively mitigates the energy level offset, passivates defects, and enhances the quality of the perovskite film. This improvement results in an outstanding efficiency of 20.1% for a 1.75 eV wide-bandgap PSC.image

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.

Conventional dye-sensitized solar cells (DSSCs) involving charge-transfer interfaces face charge injection losses and offsets for TiO2-sensitizer band alignment. The direct charge -transfer mechanism in DSSCs with catechol (CT, 1,2-benzene-diol)-based compounds minimizes the injection losses and eliminates band alignment issues, although the photovoltaic performance of the corresponding device is very poor due to the ultrafast (picosecond) recombination of photoexcited electrons. Just as in a natural photosystem, structural selectivity toward inhibition of this recombination needs to be defined. The interfacial electron density and back electron transfer kinetics at the molecular sensitizer-TiO2 interface play a significant role in the overall energy conversion efficiency. Herein, we identified, for the first time, that the ir-electron cloud at the sensitizer-TiO2 interface facilitates the degree of recombination. Comparative density functional theory analyses confirmed that these electron clouds act as large recombination sites. Luminol (LM) and isoluminol (ILM) were employed as "small molecule" sensitizers without the cloud, having a secondary amine linker, which increased the photoenergy conversion efficiency of the single-step sensitization-based photovoltaic cell (type-II DSSC) by reducing the recombination. The device with LM exhibited a power-conversion efficiency (PCE) of ca. 1.11% (representing 363% improvement when compared to CT), the highest ever reported in this category. This understanding is insightful for the design of novel small molecular sensitizers for future DSSCs.

Third-generation solar cells have gained promising momentum in recent decades as an inexpensive replacement for conventional silicon wafer-based technology. In particular, dye-sensitized solar cells (DSSCs) have attracted considerable attention owing to their simpler manufacturing procedure, inexpensiveness, and competing power conversion efficiency. The overall device performances of the DSSCs rely on four major components, which are photoanodes, sensitizing dyes, electrolytes, and counter electrodes. The final device completion constituent is the counter electrode – one of the major component, which determines the power conversion efficiency of the device. The final output of DSSCs has been measured through the counter electrode characteristics such as efficient charge transfer and reduction of electrolytes during the energy conversion process. In general, platinum (Pt) is the most commonly used counter electrode in DSSCs due to its superior catalytic property, charge transfer characteristics, and high conductivity. However, for a cost-effective solar cell application, the usage of a noble metal such as Pt is an expensive choice of candidate; and for the reduction of expensiveness, the search for alternative inexpensive material is inevitable. In this review article, we have presented the recent research developments of promising Pt-free metal chalcogenide-based counter electrodes; and the prospects in this emerging field have been discussed. In addition, this review devotes to exploring the novel concepts of various metal chalcogenides; and their composite with other materials such as metal nanoparticles, carbonaceous materials, and doped metal chalcogenide counter electrodes are described.

Perovskite solar cells (PSCs) have exhibited a tremendous photovoltaic performance over the past few years. However, the ionic nature of perovskite and the solution‐processable fabrication methods lead to various defects (vacancies, interstitials, and antisites) at the perovskite surface. Incorporating interfacial or surface passivation layers has proved to be crucial in passivating these defects. Herein, a novel donor–acceptor–donor (D–A–D)‐based bidentate material, namely, BDTBT, consisting of benzothiadiazole (BDT) as the central acceptor unit and benzothiophene (BT) as a donor end cap unit, is synthesized. The various structural analyses reveal that N and S heteroatoms at BDTBT coordinate effectively to undercoordinated Pb2+in perovskite via Pb–N/S bidentate interactions. As a result, the BDTBT‐treated perovskite exhibits an improved power conversion efficiency (PCE) of 20.42% compared with the bare perovskite, having a PCE of 17.18%. The BDTBT incorporation provides favorable band alignment, increased hole transfer, and suppressed nonradiative recombination losses by reducing the surface defect states. In addition, there is significant increase in the device stability and moisture resistance owing to the hydrophobic nature of BDTBT. This study provides a simple and efficient route to obtain stable and highly efficient PSCs by incorporating small molecules as an additional interfacial layer.

Cu2ZnSnSe4 (CZTSe) nanoparticles (NPs) are successfully synthesized via cost‐effective hot‐injection process and morphologically modified by biphasic ligand exchange method. X‐ray diffraction (XRD) results indicate kesterite phase for the as‐prepared CZTSe NPs. Scherrer equation is used to evaluate the average crystallite size (≈30 nm). Scanning electron microscopy (SEM) images reveal that the interconnected nanoflakes structure combines to produce hierarchical CZTSe nanoflower. Fourier‐transform infrared spectroscopy (FTIR) results confirm the replacement of native long‐chain ligand over the surface of NPs with inorganic salts. The optical studies reveal that the CZTSe NPs have a large absorbance over the visible region with optimum bandgap value of 1.23 eV. The photocatalytic studies confirm the high efficiency of CZTSe NPs in degrading the methylene blue (MB) dye within 120 min under visible light irradiation. The intermediate products formed during the degradation of MB have been analyzed by electrospray ionization mass spectrometry (ESI‐MS). The photocatalytic degradation mechanism is discussed.

The conventional iodine-based (I−/I3 −) electrolyte used in dye-sensitized solar cells (DSSCs) presents several limitations, such as ∼30% absorption of visible light in the wavelength range of 300–500 nm and a large potential difference between the Fermi level of I−/I3 − and the HOMO level of the dye. This has a negative impact on the characteristics of DSSC such as transparency and open circuit voltage (Voc). In the present work, a series of transparent electrolytes are prepared using various additives such as I2, LiI, guanidine thiocyanate/guanidine nitrate (GuSCN/GuNO3), and Br2 to obtain highly transparent and high voltage DSSCs. The results demonstrate that the usage of the optimized electrolyte consisting of 0.003 M Br2, 0.01 M LiI, and 0.1 M GuNO3, with the binary redox couple (I−, Br−)/(I3 −, I2Br−), contributes to an ∼25% increase in transmittance compared to that of the conventional electrolyte, while the concentration of I3 − is significantly reduced. Furthermore, the downward shift in the Fermi level of the binary redox system is shown to provide an ∼100 mV enhancement in the Voc of the DSSC compared with that of the conventional electrolyte based DSSC. In addition, the devices with the optimized binary redox system achieve a power conversion efficiency of ∼7.94% which is closely comparable to the performance of conventional (I−/I3 −) electrolyte-based DSSCs. Thus, the present study could provide immense insights toward the fabrication of high-voltage and transparent DSSCs for the application in transparent photovoltaic windows. Furthermore, by using a binary redox electrolyte, the DSSCs that operative under a 2000 lux compact fluorescent lamp (CFL) were also successfully fabricated and yielded a promising efficiency of 23.6%.

Charge transfer at the semiconductor/electrolyte interface is an important process that dictates the efficiency of quantum dots solar cells. Hole transfer kinetics remains a sluggish reaction for metal chalcogenide electrodes. In this work we examine the beneficial effect of CuxS nanoparticles on the photoelectrochemical performance of Cu-In-Zn-S (CIZS) quantum dots sensitized solar cells as they promote hole transfer to the S2-/S-n(2-) redox couple. CuxS nanoparticles if deposited without a protecting layer undergo compositional transformation in sulfur rich electrolytes. Addition of a protecting ZnS layer improves the stability and efficiency of the resulting solar cells. Establishing the hole transport property of CuxS in solar cell offers new ways to improve photovoltaic performance of QDSSC. (C) The Author(s) 2019. Published by ECS.

Two dimensional metal chalcogenides are promising candidate for optoelectronics owing to their interesting physical and chemical properties. In the present work, 2-D layer structured CuSe nanosheets were developed by simple hot injection method. Oleic acid has been employed as solvent as well as capping agent and CuCl, elemental sulfur have been used as precursors at the reaction temperature of 220OC. Crystallinity and phase of the products were characterized by X-ray diffraction (XRD). XRD patterns confirm the presence of hexagonal Klockmannite (CuSe) with space group of P63/mmc. Morphological analyses were carried out through SEM analysis which depicts the 2-D layered nanosheets of CuSe with two different orientations of nanosheets. Elemental composition of copper to selenium ratio was confirmed through Energy dispersive X-ray spectroscopy (EDS) which reveals the stoichiometry of CuSe nanosheets. The EDS results are in line with the XRD results. Optical properties were analysed through UV-Vis absorption spectroscopy in the wavelength range of 350 nm to 900 nm. The presence of capping agent over the CuSe nanosheets were confirmed from Fourier transform infrared spectroscopy (FT-IR).