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The quaternary chalcogenide Cu2NiSnS4 (CNTS) nanoparticles, made up of earth-abundant elements, are one of the most favorable in the family of CMxTS (Mx = Ni, Co, Cd, Fe, Mg, Mn, and Zn) for photoelectrochemical (PEC) hydrogen production due to the lowest resistivity, high absorption coefficient, and tunable band gap for sunlight absorption with suitable band edges. A p-type semiconductor, CNTS, is one of the stable photocathodes in the category of efficient ones. In this theoretical-aided experimental work, we illustrate the photoelectrochemical credibility of CNTS nanomaterials synthesized by a facile hot-injection method with CdS as a photoanode for hydrogen evolution with the interface of an alkaline electrolyte. Using density functional theory simulations, charge density difference, work function, and structural properties were evaluated, suggesting better lattice matching at the CNTS/CdS supercell interface with a lattice mismatch less than 3% along with better charge transfer. An optical band gap of 1.40 eV and a crystallite size of 48 nm were observed for CNTS evaluated. A high short-circuit current density of 6.656 mA cm–2 IPCE for the CNTS/CdS heterojunction was observed to be 14.87% at 505 nm. This promotes the heterojunction to possess minimal chances of material's phase change and hence stability. [ABSTRACT FROM AUTHOR]

We report the synthesis of tungsten sulfide (WS2) films using RF‐magnetron sputtering at different RF powers. X‐ray diffraction (XRD) data confirm the hexagonal crystal structure of WS2 with an average crystallite size of ∼44.54 Å. With increased RF power, the preferred orientation of WS2 crystallites shifts from (002) to (100). Linear sweep voltammetry (LSV) was used to assess the Photoelectrochemical (PEC) activity of WS2 films. The film deposited at 150 W demonstrated the highest photocurrent density of 5.44 mA/cm2. The 150 W film also showed a lower Tafel slope of ∼0.374 V/decade, indicating superior PEC activity. Mott Schottky's (MS) analysis revealed a notable shift in the flat band potential towards the negative side, suggesting a shifting of the Fermi level towards the conduction band. WS2 film grown at 150 W demonstrated a majority charge carrier density of 6.2×1021 cm−3 and a depletion layer width of 1.54 nm. The observed low charge transfer resistance of 155 Ω contributed to the enhanced PEC activity with a relaxation time constant of 37 ms. These properties suggest that WS2 can be suitable for PEC water splitting. [ABSTRACT FROM AUTHOR]

A N, N‐dimethylformamide and thiourea‐based route is developed to fabricate submicron (0.55 and 0.75 µm) thick CuIn(S,Se)2 (CISSe) thin films for photovoltaic applications, addressing challenges of material usage, throughput, and manufacturing costs. However, reducing the absorber film thickness below 1 µm in a regular CISSe solar cell decreases the device efficiency due to losses at the highly‐recombinative, and mediocre‐reflective Mo/CISSe rear interface. For the first time, to mitigate the rear recombination losses, a novel rear contacting structure involving a surface passivation layer and point contact openings is developed for solution processed CISSe films and demonstrated in tangible devices. An atomic layer deposited Al2O3 film is employed to passivate the Mo/CISSe rear surface while precipitates formed via chemical bath deposition of CdS are used to generate nanosized point openings. Consequently, Al2O3 passivated CISSe solar cells show an increase in the open‐circuit voltage (VOC) and short‐circuit current density when compared to reference cells with equivalent absorber thicknesses. Notably, a VOC increase of 59 mV contributes to active area efficiencies of 14.2% for rear passivated devices with 0.75 µm thick absorber layers, the highest reported value for submicron‐based solution processed, low bandgap CISSe solar cells. [ABSTRACT FROM AUTHOR]

SnSe nanomaterials are challenging to use in sustainable energy production due to difficulties in phase-pure synthesis and efficient charge-carrier separation. We demonstrate a systematic facile synthesis method with an in-depth nucleation and growth mechanism for the rational design of phase-pure and morphology-controlled SnSe-based efficient and cost-effective photocatalysts. Transient absorption spectroscopy measurements are performed to investigate the charge-carrier kinetics of SnSe microflowers (MFs), which exhibit a free charge-carrier lifetime of 6.2 ps. Although the bare SnSe, CdSe, and ZnSe photoanodes demonstrate sizable photocurrents, the construction of CdSe/SnSe and ZnSe/SnSe heterojunctions dramatically improves the photoelectrochemical devices activity. The CdSe/SnSe photoanode shows higher photocurrents of 35 μA cm–2, compared to the ZnSe/SnSe (15 μA cm–2) heterojunction and the individual SnSe (10 μA cm–2), CdSe (7 μA cm–2), and ZnSe (1 μA cm–2). The decent photoactivity of the CdSe/SnSe photoanode is attributed to the desired type-II band alignment and very small band offset (0.08 eV) that exists across the interface, which promotes the efficient separation of photogenerated electron–hole pairs confirmed by cyclic voltammetry measurements and is corroborated by first-principles density functional theory calculations. These findings should open new avenues for the design and development of advanced next-generation tin selenide-based heterostructures for efficient PEC water-splitting applications. [ABSTRACT FROM AUTHOR]

This study investigates the incorporation of Ba2+ at a low concentration into CsPbI2Br, resulting in the formation of mixed CsPb1−xBaxI2Br perovskite films. Photovoltaic devices utilizing these Ba-doped CsPbI2Br (Ba–CsPbI2Br) perovskite films achieved a higher stabilized power conversion efficiency of 14.07% compared to 11.60% for pure CsPbI2Br films. First-principles density functional theory calculations indicate that the improved device performance can be attributed to the efficient transport of conduction electrons across the interface between Ba–CsPbI2Br and the TiO2 electron transporting layer (ETL). The Ba–CsPbI2Br/TiO2 interface exhibits a type-II staggered band alignment with a smaller conduction band offset (CBO) of 0.25 eV, in contrast to the CsPbI2Br/TiO2 interface with a CBO of 0.48 eV. The reduced CBO at the Ba–CsPbI2Br/TiO2 interface diminishes the barrier for conduction electrons to transfer from the Ba–CsPbI2Br layer to the TiO2 layer, facilitating efficient charge transport. [ABSTRACT FROM AUTHOR]

In this work, we develop a photocatalyst wherein nitrogen and phosphorus co-doped carbon quantum dots are scaffolded onto TiO2 nanoparticles (NPCQD/TiO2), denoted as NPCT hereafter. The developed NPCT photocatalyst exhibits an enhanced visible light photocatalytic hydrogen production of 533 μmol h−1 g−1 compared to nitrogen doped CQD/TiO2 (478 μmol h−1 g−1), phosphorus doped CQD/TiO2 (451 μmol h−1 g−1) and pure CQD/TiO2 (427 μmol h−1 g−1) photocatalysts. The enhanced photocatalytic activity of the NPCT photocatalyst is attributed to the excellent synergy between NPCQDs and TiO2 nanoparticles, which results in the creation of virtual energy levels, a decrease in work function and suppressed recombination rates, thereby increasing the lifetime of photogenerated electrons. A detailed mechanism is proposed for the enhancement in visible light hydrogen production by the NPCT photocatalyst from the experimental results, Mott–Schottky plots and ultraviolet photoelectron spectroscopy results. Further, first-principles density functional theory (DFT) simulations are carried out which predict the decrease in the work function and band gap, and the increase in the density of states of NPCT as the factors responsible for the observed enhancement in visible light photocatalytic hydrogen production. [ABSTRACT FROM AUTHOR]

Semiconductors based on bismuth halides have gained attention for a wide range of electronic applications, including photovoltaics, light-emitting diodes, and radiation detectors. Their appeal is due to their low toxicity, high environmental stability under ambient conditions, and easy processability by a wide range of scalable methods. The performance of Bi-based semiconductors is dictated by electron–phonon interactions, which limit carrier mobilities and can also influence optoelectronic performance, for example, by giving rise to a large Stokes shift for photoluminescence, unavoidable energy loss channels, or shallow optical absorption onsets. In this Perspective, we discuss the recent understanding of how polarons and self-trapped excitons/carriers form in Bi-based semiconductors (particularly for the case of Cs2AgBiBr6), their impact on the optoelectronic properties of the materials, and the consequences on device performance. Finally, we discuss the opportunities that control of electron–phonon coupling enables, including stable solid-state white lighting, and the possibilities of exploiting the strong coupling found in bipolarons for quantum technologies. [ABSTRACT FROM AUTHOR]

Organic–inorganic lead halide perovskites (OIHPs) have emerged as promising materials for next‐generation photovoltaics. However, performance improvements in the perovskite‐based device are still limited due to defects that exist more intensively on the surface as well as grain boundaries (GBs) and mismatching energy levels at the interface. Herein, a reactive post‐treatment process (RPP) using guanidine acetate (GA) is adopted to address defects and interfacial energy level matching at the perovskite surface. The RPP with GA (GA‐RPP) results in the formation of an improved perovskite layer with large grain size and low GB density, leading to the formation of secondary phases on the perovskite surface with appropriate energy levels, resulting in reduced defect density and charge recombination. Furthermore, density functional theory analysis reveals that the Pb‐rich secondary phase could improve the conduction of electrons at the perovskite interface. Therefore, the GA‐RPP‐based perovskite‐based solar cell (PSC) shows enhanced performance with 20.4% efficiency and long‐term stability. [ABSTRACT FROM AUTHOR]

Layered binary semiconductor materials have attracted significant interest as field emitters due to their low work function, mechanical stability, and high thermal, and electrical conductivity. Herein, we report a systematic experimental and theoretical investigation of SnS nanoflakes synthesized using a simple, low-cost, and non-toxic hot injection method for field emission studies. The field emission studies were carried out on SnS nanoflake thin films prepared using a simple spin coating technique. The X-ray diffraction (XRD) and Raman spectroscopy analysis revealed an orthorhombic phase of SnS. Scanning electron microscopy (SEM) analysis revealed that as-synthesized SnS has a flakes like morphology. The formation of pure-phase SnS nanoflakes was further confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The UV-Visible-NIR spectroscopy analysis shows that SnS nanoflakes have a sharp absorption edge observed in the UV region and have a band gap of ∼1.66 eV. In addition, the first-principles density functional theory (DFT) calculations were carried out to provide atomic-level insights into the crystal structure, band structure, and density of states (DOS) of SnS nanoflakes. The field emission properties of SnS nanoflakes were also investigated and it was found that SnS nanoflakes have a low turn-on field (∼6.2 V μm−1 for 10 μA cm−2), high emission current density (∼104 μA cm−2 at 8.0 V μm−1), superior current stability (∼1 μA for ∼2.5 hrs), and a high field enhancement factor of 1735. First principles calculations predicted lower work function for different surfaces, especially for the most stable SnS (001) surface (φ = 4.32 eV), which is believed to be responsible for the observed facile electron emission characteristics. We anticipate that the SnS could be utilized for future vacuum nano/microelectronic and flat panel display applications due to the low turn-on field and flakes like structure. [ABSTRACT FROM AUTHOR]

Lead‐free double perovskites have emerged as stable and non‐toxic alternatives to Pb‐halide perovskites. Herein, the synthesis of Fe‐doped Cs2AgBiCl6 lead‐free double perovskites are reported that display blue emission using an antisolvent method. The crystal structure, morphology, optical properties, band structure, and stability of the Fe‐doped double perovskites were investigated systematically. Formation of the Fe‐doped Cs2AgBiCl6 double perovskite is confirmed by X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) analysis. XRD and thermo‐gravimetric analysis (TGA) shows that the Cs2AgBiCl6 double perovskite has high structural and thermal stability, respectively. Field emission scanning electron microscopy (FE‐SEM) analysis revealed the formation of dipyramidal shape Cs2AgBiCl6 crystals. Furthermore, energy‐dispersive X‐ray spectroscopy (EDS) mapping shows the overlapping of Cs, Bi, Ag, Fe, and Cl elements and homogenous incorporation of Fe in Cs2AgBiCl6 double perovskite. The Fe‐doped Cs2AgBiCl6 double perovskite shows a strong absorption at 380 nm. It extends up to 700 nm, suggesting that sub‐band gap states transition may originate from the surface defect of the doped perovskite material. The radiative kinetics of the crystals was studied using the time‐correlated single‐photon counting (TCSPC) technique. Lattice parameters and band gap value of the Fe‐doped Cs2AgBiCl6 double perovskites predicted by the density functional theory (DFT) calculations are confirmed by XRD and UV/Visible spectroscopy analysis. Time‐dependent photo‐response characteristics of the Fe‐doped Cs2AgBiCl6 double perovskite show fast response and recovery time of charge carriers. We believe that the successful incorporation of Fe in lead‐free, environmentally friendly Cs2AgBiCl6 double perovskite can open a new class of doped double perovskites with significant potential optoelectronics devices fabrication and photocatalytic applications. [ABSTRACT FROM AUTHOR]