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The surface electric field (F) of β-FeSi2 has been investigated by Franz–Keldysh oscillations (FKOs) observed in photoreflectance spectra. The FKO signals were observed in an undoped β-FeSi2 epitaxial layer (3 nm) grown on p+-type β-FeSi2 layers (UP+ structure) by molecular beam epitaxy. The surface electric field obtained from the FKO at 11 K was F = 220 kV/cm. The surface electric field was almost independent of the excitation light power and temperature, showing that the surface electric field was not affected by the surface photovoltage effect. In the dependence of F on the thickness of the undoped layer (d), F was nearly constant at d = 2–56 nm. The result showed that the surface electric field of β-FeSi2 was applied to a thin region (<2 nm) at the surface. [ABSTRACT FROM AUTHOR]

Carbon-based Materials have been extensively researched for their prospect in the fields of environment and energy, especially for graphene oxide (GO). In this work, a novel sodium dodecyl sulfate (SDS)-assisted synthesis of BiOBr/Bi2WO6/GO ternary composite has been synthesized successfully by a handy hydrothermal method. Photoluminescence, Photocurrent, Electrochemical Impedance Spectroscopy, surface photovoltage and transient photovoltage measurements illustrate that construction of p-n BiOBr/Bi2WO6 heterojunction leads to the obviously enhancement of charge separation efficiency, and the photogenerated electrons trapped by GO can effectively inhibit the recombination process of photogenerated charge, resulting in the improvement of charge separation efficiency and the longer lifetime of photogenerated carriers for BiOBr/Bi2WO6/GO. The characterization of structure and morphology indicate that role of GO can also improve the visible light absorption range, and the SDS-assisted synthesis can reduce the size of particle in the composite and enhances the specific surface area of the composite by regulating the particle size and agglomeration. Under optimal conditions, BiOBr/Bi2WO6/GO (SDS) has the outstanding photocatalytic degradation performance and the degradation rate constants for oxytetracycline, tetracycline hydrochloride, methylene blue and rhodamine are 0.056, 0.057, 0.103 and 0.414 min−1, respectively. Notably, the degradation rate constants obtained by BiOBr/Bi2WO6/GO (SDS) are more ten times higher than that of pure BiOBr and Bi2WO6. The possible mechanism of photocatalytic degradation was suggested for BiOBr/Bi2WO6/GO based on the dynamic properties of photogenerated charge and reactive oxidation species results. Surprisingly, the recyclability of the BiOBr/Bi2WO6/GO (SDS) composite obtained from the cyclic experiments has laid a foundation for the study of efficient and stable photocatalysts. [ABSTRACT FROM AUTHOR]

Photocatalytic oxygen reduction reaction (ORR) is an environmentally friendly and cost‐effective approach for H2O2 synthesis. However, the current photosynthesis system suffers from sluggish kinetics, rapid recombination of photoexcited charge carriers, and weak redox potentials, resulting in unsatisfactory solar‐to‐chemical conversion efficiency. Herein, a Z‐scheme heterojunction (UiO/IKCN) is constructed through coupling I−/K+ co‐doped g‐C3N4 (IKCN) with NH2‐UiO‐66, a typical metal‐organic framework material. Under visible light irradiation, the optimal UiO/IKCN exhibits exceptional H2O2 production rates in pure water (13.3 mM g−1 h−1) and in isopropanol solution (72.6 mM g−1 h−1), that is 48.4 times higher than pristine CN in isopropanol (1.5 mM g−1 h−1). A high apparent quantum yield of 10.28% at 420 nm is achieved by UiO/IKCN, surpassing most previously reported values. The dominating role of two‐electron ORR in H2O2 photosynthesis is elucidated in detail. The significantly enhanced photocatalytic activity can be attributed to the facilitated charge separation and Z‐scheme charge transfer, which are unambiguously verified by stable‐state surface photovoltage, transient photoluminescence, femtosecond transient absorption spectroscopy, in‐situ irradiated X‐ray photoelectron spectroscopy, and density functional theory calculations. This study represents the first exploration of H2O2 production using NH2‐UiO‐66 and provides insights into the rational design of Z‐scheme heterojunction for highly efficient photosynthesis. [ABSTRACT FROM AUTHOR]

Hybrid Perovskite materials have gone through an astonishing development due to their unique optoelectronic behavior, leading to the creation of a wide range of synthetic strategies. As the materials’ surface is found to play a crucial role with respect to the properties, e.g. hydration, stability and carrier mobilities, considerable efforts have been made to optimize the surface through various approaches. Especially the passivation of the perovskite surface attracted a lot of attention in this field, often resulting in more complex, multi‐step synthetic processes. In this study, a simple one‐step aerosol‐assisted synthetic approach is presented to obtain thiocyanate (SCN) passivated single‐crystal MAPbBr3 microcrystals. To elucidate the role of the additive in the crystallization process, mixed (pseudo‐)halide precursors are systematically investigated. The as processed, passivated microcrystals exhibit enhanced stability and charge carrier lifetimes. Additionally, a decrease in surface photovoltage, attributed to the presence of the SCN additive, is observed. Furthermore, the aerosol process is further developed resulting in a novel binary system containing MAPbBr3‐SCN perovskite microcrystals and Au nanostructures. This system serves as a promising model for further investigations into potential interactions between plasmonic and semiconducting materials, with initial results indicating prolonged charge carrier lifetimes. [ABSTRACT FROM AUTHOR]

In the present study, the minority carrier diffusion length (MCDL), determined by surface photovoltage spectroscopy measurements, is compared in n‐ and p‐type Si wafers after their oxidation under different conditions using various tools (horizontal and vertical furnaces, atomic layer deposition (ALD), low‐pressure chemical vapor deposition, and plasma‐enhanced chemical vapor deposition). It is shown that MCDL varies significantly depending on the design of furnaces, oxidation temperatures, the type of gases used before and during oxidation, and their flow ratios. The type and crystal growth method of Si wafers used for the oxidation also play a significant role and influence MCDL. Additionally, MCDL after the deposition of alumina layers using ALD techniques is found to be significantly larger compared to that observed after the thermal oxidation of Si. The larger values of MCDL after the ALD of Al2O3 are detected independent of temperature and precursors used for the deposition. The origin of different MCDL values after various oxidation processes, with an emphasis on the formation of electrically active defects in Czochralski (CZ)‐ and float‐zone (FZ)‐grown Si wafers is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] The anchoring sites of metal single atoms are closely related to photogenerated carrier dynamics and surface reactions. Achieving smooth photogenerated charge transfer through precise design of single-atom anchoring sites is an effective strategy to enhance the activity of photocatalytic hydrogen evolution. In this study, Pt single atoms were loaded onto ultra-thin carbon nitride with two-coordination nitrogen vacancies (V N2c -UCN-Pt) and ultra-thin carbon nitride with three-coordination nitrogen vacancies (V N3c -UCN-Pt). This paper investigated the photocatalytic hydrogen evolution performance and photogenerated carrier behavior of Pt single atoms at different anchoring sites. Surface photovoltage measurements indicated that V N2c -UCN-Pt exhibits a superior carrier separation efficiency compared to V N3c -UCN-Pt. More importantly, the surface photovoltage signal under the presence of H 2 O molecules revealed a significant decrease. Theoretical calculations suggest that V N2c -UCN-Pt exhibits superior capabilities in adsorbing and activating H 2 O molecules. Consequently, the photocatalytic hydrogen evolution efficiency of V N2c -UCN-Pt reaches 1774 µmol g−1h−1, which is 1.8 times that of V N3c -UCN-Pt with the same Pt loading. This work emphasized the structure–activity relationship between single-atom anchoring sites and photocatalytic activity, providing a new perspective for designing precisely dispersed single-atom sites to achieve efficient photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Spatially-ordered MoSe 2 /CdS intimate S-scheme heterojunction was constructed, which exhibited an outstanding photocatalytic capability due to the strengthened built-in electric field via Fermi level modulation with donor (Se vacancies) and acceptor (Mo5+) impurities. [Display omitted] • Multi-armed MoSe 2 /CdS Z-scheme heterojunction with intimate Mo-S bond connection. • Se vacancies and Mo5+ serve as donor and acceptor impurities of MoSe 2. • Strengthened built-in electric field of MoSe 2 /CdS via Fermi level modulation. • Excellent HER rate (52.62 mmol·g−1·h−1) and AQE (34.8 % at 400 nm) are achieved. • Outstanding H 2 production stability confirmed by cycling and long-term tests. Spatially-ordered S-scheme photocatalysts are intriguing due to their enhanced light harvesting, spatially isolated redox sites, and strong redox abilities. Nonetheless, heightening the performance of S-scheme photocatalysts via controllable defect engineering is still challenging to now. In this work, multi-armed MoSe 2 /CdS S-scheme heterojunction with intimate Mo-S bond coupling and adjustable Se vacancies (V Se) and Mo5+ concentrations was constructed, which consisted of few- or even single-layered MoSe 2 growing on the {11–20} facets of wurtzite CdS arms. The S-scheme charge transmission mechanism of MoSe 2 /CdS heterojunction was validated by density functional theory calculation combined with in situ photo-irradiated X-ray photoelectron spectroscopy, surface photovoltage, and radical measurements. Moreover, the Fermi level gap between CdS and MoSe 2 was enlarged by regulating the contents of donor (V Se) and acceptor (Mo5+) impurities with synthesis temperature, which strengthens the built-in electric field and carriers transfer driving force of MoSe 2 /CdS composites, contributing to an outstanding H 2 evolution activity of 52.62 mmol·g−1·h−1 (corresponding to an apparent quantum efficiency of 34.8 % at 400 nm) under visible-light irradiation (λ > 400 nm), 25.8 times that of Pt-loaded CdS counterpart and a substantial amount of reported CdS-containing photocatalysts. Our study results are anticipated to facilitate the rational design of advanced semiconductor nanostructures for efficient solar conversion and utilization. [ABSTRACT FROM AUTHOR]

Porous SrTiO 3 single crystals with (0 0 1) facets were synthesized using carbon spheres as templates via hydrothermal method, exhibiting boosted photocatalytic overall water splitting (POWS) due to the numerous pore walls acting as "highways" to facilitate carrier transfer. [Display omitted] Suppressing carrier recombination in bulk and facilitating carrier transfer to surface via rational structure design is of great significance to improve solar-to-H 2 conversion efficiency. We demonstrate a facile hydrothermal method to synthesize porous SrTiO 3 single crystals (SrTiO 3 -P) with exposed (0 0 1) facets by introducing carbon spheres as templates. The obviously increased surface photovoltage and photocurrent response indicate that the interconnected pore walls act as enormous charge transfer "highways", accelerating carrier transport from bulk to surface. Furthermore, the absence of grain boundaries and high crystallinity could also lower the carrier recombination rate. Thus, the SrTiO 3 -P photocatalyst loaded with Rh/Cr 2 O 3 as cocatalyst exhibits 1.5 times higher overall water splitting activity than that of solid SrTiO 3 , with gas evolution rate of 19.99 μmol h−1 50 mg−1 for H 2 and 11.37 μmol h−1 50 mg−1 for O 2. Additionally, SrTiO 3 -P also shows superior stability without any decay during cycling testing. This work provides a new insight into designing efficient multicomponent photocatalysts with a single-crystal porous structure. [ABSTRACT FROM AUTHOR]

Till date it is a great challenge to synthesize CdS photocatalyst with a high stability. In this study, a stable CdS photocatalyst was successfully synthesized by a simple, cost‐effective hydrothermal route via cadmium acetate and thiourea as Cd and S precursors, respectively. The effect of different processing times (8 h and 24 h) and molar ratios on the photocatalytic activity and stability were mainly investigated. The samples were characterized in detail by XRD, FT‐IR, XPS, UV‐vis DRS, Photolummiscence spectroscopy and Surface photovoltage. The photocatalytic activity of the as‐obtained nanostructures was examined for methylene blue (MB) dye degradation under visible light irradiation (λ≥420 nm). After 70 min of irradiation, nearly 82 % of MB was degraded by CdS nanostructures, display an improved photocatalytic activity for MB degradation with an apparent rate constant (k) of 0.019 min−1. Additionally, CdS nanostructures sustained a good photostability after five consecutive cycles. The higher photocatalytic activity of CdS nanostructure is attributed to an efficient separation of photogenerated electron‐hole pairs stimulated by its optimal molar ratio, optimal temperature and surface morphology. Our synthesized stable nanostructures have potential for dye contaminated waste‐water treatment. [ABSTRACT FROM AUTHOR]

The efficient functioning of perovskite solar cells largely depends on the interaction between perovskite halide materials and the hole‐transport layer poly(3‐hexylthiophene) (P3HT). However, a high rate of nonradiative recombination often hampers this interaction, leading to poor performance of the solar cells. We have developed a technique to modify the interface using a long‐chain alkyl halide molecule called n‐hexyl trimethylammonium bromide to address this issue. This modification technique significantly improves hole extraction, leading to an impressive open‐circuit voltage of 1.14 V and a power conversion efficiency of 15.8% for inorganic perovskite CsPbI3 with P3HT as a dopant‐free hole‐transport layer. This breakthrough can pave the way for developing more efficient and sustainable solar cells. [ABSTRACT FROM AUTHOR]

CdS, as an important photocatalytic degradation material, exhibits certain limitations. In our study, carbon nitride/cadmium sulfide (C3N5/CdS) nanocomposites were synthesized via an in-situ method, and the crystalline structure, composition, and morphology of the hybrid samples were evaluated using various techniques. The development of the Z-scheme heterojunction in the C3N5/CdS composite photocatalyst facilitated more effective separation of photogenerated charges, resulting in higher photocatalytic degradation efficiency. Under visible light irradiation at 425 nm, the composite with a 1:1 ratio exhibited the best degradation performance, achieving degradation rates of 93.8% for methyl orange solution and 96.8% for rhodamine B solution. Additionally, the introduction of C3N5 significantly reduced the photocorrosion of CdS. These experimental results were confirmed by fluorescence analysis, surface photovoltage (SPV) measurements, electrochemical tests, etc. [ABSTRACT FROM AUTHOR]

An ultranarrow‐band ultraviolet (UV) GaN detector with a simple device architecture is presented. The device displays an ultranarrow band response centred at 366 nm with only ≈5 nm width, a UV–visible rejection ratio of >2 × 103, and detectivity of 1.3 × 1010 Jones at room temperature. The device is tested over a wide temperature range where the maximum response is recorded at 200 K. Temperature dependence of device response is explained by considering the thermal activation of shallow donors in low‐temperature regime and the establishment of thermal equilibrium of the donor level with conduction band at elevated temperatures. Moreover, the device displays three orders UV‐to‐visible rejection ratio over a wide temperature range of 150–350 K, showing great potential for narrowband UV detection even at elevated temperatures. Conventional and pump‐probe surface photovoltage spectroscopy measurements are performed with UV and infrared lasers to identify the electronic transitions associated with the narrowband response. It is understood that carrier excitation from valance band to shallow donor level in the interfacial depletion region is responsible for the observed behavior. The results presented here demonstrate an innovative methodology for achieving a stable and high spectrum‐selective UV photodetection without involving complex device architecture. [ABSTRACT FROM AUTHOR]

The performance of conventional methylammonium (MA)‐based perovskite solar cells (PSCs) and their MA‐free counterparts showcase explicit divergence in device performance often stemming from crucial open‐circuit voltage (VOC) deficits while employing NiOx hole‐transport layer (HTL). In this work, the performance of MAPbI3 and FA0.9Cs0.1PbI3 based PSCs are correlatively analyzed using surface photovoltage (SPV) and photocurrent density (Jph) studies for the first time to quantify hole selectivity and contact passivation of NiOx HTL when used in conjunction with distinct perovskite compositions. In the findings of the study, it is shown that the perovskite composition is a major determinant of NiOx HTL's carrier selectivity by regulating quasi‐Fermi level (QFL) equilibration at the absorber/HTL interface. Higher charge collection probability and SPV shown by methylammonium (MA)‐free devices highlight the suppressed formation of PbI2‐rich hole‐extraction barrier at FACsPbI3/HTL interface as opposed to MAPbI3/HTL interface, in‐turn establishing a trade‐off between carrier selectivity and contact passivation of NiOx HTL. These experimental quantifications help in understanding the evolution of internal QFL splitting and external VOC of devices employing NiOx HTL for varied perovskite composition. Therefore, to maximize the performance of PSCs, the findings of the study emphasize the significance of tailoring the energetics and kinetics at the perovskite/HTL interfaces. [ABSTRACT FROM AUTHOR]

Hollow semiconductor nanostructures with direct Z-scheme heterojunction have significant advantages for photocatalytic reactions, and optimizing the interfacial charge transmission of Z-scheme heterojunction is the hinge to achieve excellent solar conversion efficiency. In this work, tubular Ni1-xCoxS2-CdS heterostructures with reinforced Z-scheme charge transmission were constructed through an In-metal-organic framework (MOF) templated strategy. The Z-scheme charge transfer mechanism was sufficiently confirmed by combining density functional theory (DFT) calculation, X-ray photoelectron spectroscopy (XPS), surface photovoltage spectroscopy (SPV), and radical testing results. Crucially, the use of sodium citrate complexant contributes to the formation of intimate heterointerface, and the Fermi level gap between CdS and NiS2 is enlarged through Co doping into NiS2, which enhances the built-in electric field and photo-carriers transmission driving force for Ni1-xCoxS2-CdS heterojunction, resulting in an evidently promoted activity toward H2 evolution reaction (HER). Under visible-light (λ > 400 nm) irradiation, the Ni1-xCoxS2-CdS composite with 10 mol% Co doping and 80 wt.% CdS (NC0.10S-80% CdS) achieved an outstanding HER rate up to 35.94 mmol·g-1·h-1 (corresponding to the apparent quantum efficiency of 34.7% at 420 nm), approximately 76.4 times that of 3 wt.% Pt-loaded CdS and it is much superior to that of most CdS-based photocatalysts ever reported. Moreover, the good photocatalytic durability of Ni1-xCoxS2-CdS heterostructures was validated by cycling and long-term HER tests. This work could inspire the development of high-performance Z-scheme heterojunction via optimizing the morphology and interfacial charge transmission. [ABSTRACT FROM AUTHOR]

CuNb2O6 (CNO), a novel ternary metal oxide, has garnered much attention since it has a modest bandgap and potentially high current density. However, the reported photocurrent density so far is still much lower than the theoretical value. In this study, a CuO/CNO photoelectrode heterojunction was synthesized for the first time by using a solution‐based spray pyrolysis method. The properties of the heterojunction were investigated through various characterization techniques, including Mott‐Schottky analysis, time‐resolved photoluminescence, surface photovoltage analysis, chopper linear sweep voltammetry, and electrochemical impedance spectroscopy. The optimized maximum photocurrent density of the CuO/CNO heterojunction was ~0.75 mA/cm2 at 0.4 V vs. reversible hydrogen electrode (RHE), which is 2.8 times higher compared to the bare CNO photocathode. The improvement is attributed to the enhanced transport properties of charge carriers and promoted better separation of photo‐generated electrons and holes in the photoelectrode by the heterostructure. By the generation of heterojunctions, this work provides a new foundation for the design and construction of photocathodes with high charge separation efficiencies. This is also useful for future studies on water decomposition using heterojunctions as photoelectrode materials. [ABSTRACT FROM AUTHOR]

Mild-temperature nitrogen-doping could flatten the pristine upward band bending without triggering the formation of Ti3+, thus enhancing the visible-light-responsiveness of nitrogen doped TiO 2. [Display omitted] Herein, a mild-temperature nitrogen doping route with the urea-derived gaseous species as the active doping agent is proposed to realize visible-light-responsive photocatalytic hydrogen evolution both for the anatase and rutile TiO 2. DFT simulations reveal that the cyanic acid (HOCN), derived from the decomposition of urea, plays a curial role in the effective doping of nitrogen in TiO 2 at mild temperatures. Photocatalytic performance demonstrates that both the anatase and rutile TiO 2 doped at mild temperatures exhibit the highest hydrogen evolution rates, although the ones prepared at high temperatures possess higher absorbance in the visible range. Steady-state and transient surface photovoltage characterizations of these doped TiO 2 polymorphs prepared at different temperatures reveal that harsh conditions (high temperature reaction) typically result in the formation of intrinsic defects that are detrimental to the transport of the low-energy visible-light-induced electrons, while the mild-temperature nitrogen-doping could flatten the pristine upward band bending without triggering the formation of Ti3+, thus achieving enhanced visible-light-responsive hydrogen evolution rates. We anticipate that our findings will provide inspiring information for shrinking the gap between the visible-light-absorbance and the visible-light-responsiveness in the band engineering of wide-bandgap metal-oxide photocatalysts. [ABSTRACT FROM AUTHOR]

Abstract This research delves into the effects of 2D layers on the functionality of 3D perovskite using lock‐in amplifier‐based in situ surface photovoltage (SPV) and its phase spectroscopy, with an emphasis on elucidating the connection between the tuning of dipole moments and the photocurrent hysteresis. Conventionally, the SPV of a perovskite/hole transport layer is observed to diminish as positive bias escalates. However, this trend is reversed in the case of 3D perovskite samples, where an augmentation in SPV is noted under positive bias. Notably, 3D/2D perovskite structures initially show a decrease, then an increase in SPV as bias intensifies, a phenomenon more pronounced with larger dipole moments in 2D. However, there is no linear relationship between the dipole moment and the hysteresis factor. Furthermore, using in situ light‐chopping‐frequency‐modulated SPV and Kelvin Probe Force Microscopy, it is revealed that the dipole fields of 2D layers can hinder ion migration. This leads to efficient hole transfer and minimal photocurrent hysteresis in 3D/2D perovskites, providing strong evidence for the underlying cause of hysteresis. Additionally, these findings suggest intricate interplays among the external electric field, interface dipole moments, and surface photovoltaics, offering significant insights into perovskite optoelectronics.

Understanding the transport of photogenerated charge carriers in semiconductors is crucial for applications in photovoltaics, optoelectronics, and photo-detectors. While recent experimental studies using scanning ultrafast electron microscopy (SUEM) have demonstrated that the local change in the secondary electron emission induced by photoexcitation enables direct visualization of the photocarrier dynamics in space and time, the origin of the corresponding image contrast still remains unclear. Here, we investigate the impact of photoexcitation on secondary electron emissions from semiconductors using a Monte Carlo simulation aided by time-dependent density functional theory. Particularly, we examine two photoinduced effects: the generation of photocarriers in the sample bulk and the surface photovoltage (SPV) effect. Using doped silicon as a model system and focusing on primary electron energies below 1 keV, we found that both the hot photocarrier effect immediately after photoexcitation and the SPV effect play dominant roles in changing the secondary electron yield (SEY), while the distribution of photocarriers in the bulk leads to a negligible change in SEY. Our work provides insights into electron–matter interaction under photo-illumination and paves the way toward a quantitative interpretation of the SUEM contrasts. [ABSTRACT FROM AUTHOR]

The design and development of smart materials in developing advanced sensing platforms for volatile organic compounds (VOCs) have attracted increasing attention. π-Conjugated small organic building blocks, which can self-assemble into well-ordered superstructures, offer multiple advantages of high surface area, unique optoelectronic properties, good chemical/thermal stability, and host–guest interaction ability, which make them appealing candidates for VOC sensing. However, the fabrication of stable and well-ordered self-assembled structures from π-conjugated building blocks with appreciable electrical properties and their successful employment in the selective detection of VOCs remains a challenge due to the non-specific interaction between monomers during self-assembly and with other existing VOCs during sensing, respectively. Herein, we have designed and synthesized three phenanthro[9,10-d] imidazole-based ligands; L1, L2, and L3 with three different hydroxy benzene analog substitutions at the 2-position and their corresponding Zn(II) and Cd(II) complexes followed by fabrication into well-ordered superstructures with discrete morphologies for the selective detection of acetone vapour by measuring the contact potential difference using the Scanning Kelvin Probe (SKP). Several experimental analyses suggest that a precise combination of the operative non-covalent interactions along with the metal–ligand interactions drive the overall self-assembly process of these metal coordinated π-conjugated probes and could lead to generation of well-ordered various superstructures. Surface photovoltage measurements using the SKP on the surfaces of films coated with superstructures derived from these metal complexes were carried out both in the dark and under UV (Ultra-Violet) illumination in the presence of different vapours of VOCs. As per the results, under UV illumination, the thin film fabricated with superstructures derived from Cd complexes ((L1)2M, (L2)2M and (L3)2M; M = Cd(II)) exhibit higher sensitivity and selectivity towards acetone in comparison with Zn(II) complexes-based superstructures. Thus, these self-assembled structures generated by the metal complexes of these π-conjugated molecular probes may provide new insights into the fabrication of organic electronic devices for gas sensors. [ABSTRACT FROM AUTHOR]

Spatially-ordered 1D nanocrystal-based semiconductor nanostructures possess distinct merits for photocatalytic reaction, including large surface area, fast carrier separation, and enhanced light scattering and absorption. Nevertheless, establishing a valid photo-carrier transmission channel is still crucial yet challenging for semiconductor heterostructures to realize efficient photocatalysis. In this work, spatially ordered NiOOH-ZnS/CdS heterostructures were constructed by sequential ZnS coating and NiOOH photo-deposition on multi-armed CdS, which consists of {112¯0}-faceted wurtzite nanorods grown epitaxially on {111}-faceted zinc blende core. Intriguingly, the surface photovoltage spectroscopy and PbO2 photo-deposition results suggest that the photogenerated holes of CdS were first transferred to the Zn-vacancy level of ZnS and then to NiOOH, as driven by the built-in electric field between ZnS and CdS and the hole-extracting effect of the NiOOH cocatalyst, leading to the efficient charge separation of NiOOH-ZnS/CdS. With visible-light (λ > 420 nm) irradiation, NiOOH-ZnS/CdS exhibited a distinguished H2-evolution rate of 152.20 mmol g−1 h−1 (apparent quantum efficiency of 40.9% at 420 nm), approximately 18 folds that of 3 wt% Pt-loaded CdS and much higher than that of ZnS/CdS and NiOOH-CdS counterparts as well as the most reported CdS-containing photocatalysts. Moreover, the cycling and long-term H2 generation tests manifested the outstanding photocatalyst stability of NiOOH-ZnS/CdS. The study results presented here may propel the controllable design of highly-active nanomaterials for solar conversion and utilization. [ABSTRACT FROM AUTHOR]

Optically active color centers in diamonds have been intensively studied due to their potential in photonics, energy harvesting, biosensing, and quantum computing. Silicon vacancy (SiV) center offers an advantage of suitable emission wavelength and narrow zero‐phonon line at room temperature. Measurement of surface potential and photovoltage can provide better understanding of the physics and control of SiV light emission, such as charge states and charging effects. Herein, optoelectronic properties of nanocrystalline diamond films with SiV centers at different layer thicknesses (10–200 nm, controlled by the growth time) under ambient conditions are studied. Time‐dependent measurements are performed in the light–dark–light cycle. Positive photovoltage arises on samples with SiV layer thicknesses below 55 nm on both H‐ and O‐terminated surfaces. Above 55 nm the photovoltage switches to negative. This layer thickness thus represents a halfway boundary between surface‐controllable and bulk SiV centers dominant contribution. A band diagram scheme explaining the photovoltage switching mechanism is provided. [ABSTRACT FROM AUTHOR]

In this study, we systematically investigated the effect of single-atom gold (Au) loaded on ZnIn2S4 nanosheets on the photocatalytic reduction of carbon dioxide (CO2). Utilizing a photodeposition method, we successfully dispersed single-atom Au uniformly on the surface of ZnIn2S4 nanosheets. Under simulated sunlight irradiation, the Au-loaded catalyst demonstrated a higher yield and selectivity in the CO2 reduction reaction compared to the pure ZnIn2S4 nanosheets. Surface photovoltage testing revealed that the addition of Au significantly enhanced the separation efficiency of photo-generated charge carriers, thereby improving the photocatalytic efficiency. Density functional theory calculations indicated that the loading of single-atom Au reduced the reaction energy barrier from CO2 to CO, enhancing the selectivity of photocatalytic CO2 reduction. This research not only developed an efficient catalyst for CO2 reduction but also provided deep insights into the mechanism of single-atom catalysts in the photocatalytic CO2 reduction process through extensive experimental and theoretical analysis. [ABSTRACT FROM AUTHOR]

Understanding electron and ion dynamics is an important task for improving modern energy materials, such as photovoltaic perovskites. These materials usually have delicate nano‐ and microstructures that influence the device parameters. To resolve detailed structure–function relationships on the relevant micro‐ and nanometer length scales, the current macroscopic and microscopic measurement techniques are often not sufficient. Here, nanoscale surface photovoltage spectroscopy (nano‐SPV) and nanoscale ideality factor mapping (nano‐IFM) via time‐resolved Kelvin probe force microscopy are introduced. These methods can map nanoscale variations in charge carrier recombination, ion migration, and defects. To show the potential of nano‐SPV and nano‐IFM, these methods are applied to perovskite samples with different morphologies. The results clearly show an improved uniformity of the SPV and SPV decay distribution within the perovskite films upon passivation and increasing the grain size. Nevertheless, nano‐SPV and nano‐IFM can still detect local variations in the defect density on these optimized samples, guiding the way for further optimization. [ABSTRACT FROM AUTHOR]

The dynamics of photoexcited carriers in magnetron sputtered ZnO films is characterized employing time-domain impedance analysis, which is based on the measurements of the surface photovoltage (SPV) transients. The studies focus on observing the damage after the implantation of Nd+ ions in ZnO layers and a subsequent anneal. We observed the positive and negative components of the measured SPV transient and develop equivalent circuits of the structure involving multiple series of parallel resistance (R), capacitance (C), and inductance (L) elements, and derive a simple fitting procedure which allows to reproduce accurately the measured SPV transient. The relationship between these RCL elements and a rough physical picture of the charge transport phenomena in the interface regions of the structure is envisaged. This approach is conceptually useful for characterizing interfaces in semiconductor structures and devices. [ABSTRACT FROM AUTHOR]

Designing photocatalysts with efficient charge separation and electron transport capabilities to achieve efficient visible-driven hydrogen production remains a challenge. Herein, 2D–2D conductive metal–organic framework/g-C3N4 heterojunctions were successfully prepared by an in situ assembly. Compared to pristine g-C3N4, the ratio-optimized Ni-CAT-1/g-C3N4 exhibits approximately 3.6 times higher visible-light H2 production activity, reaching 14 mmol g−1. Through investigations using time-resolved photoluminescence, surface photovoltage, and wavelength-dependent photocurrent action spectroscopies, it is determined that the improved photocatalytic performance is attributed to enhanced charge transfer and separation, specifically the efficient transfer of excited high-energy-level electrons from g-C3N4 to Ni-CAT in the heterojunctions. Furthermore, the high electrical conductivity of Ni-CAT enables rapid electron transport, contributing to the overall enhanced performance. This work provides a feasible strategy to construct efficient dimension-matched g-C3N4-based heterojunction photocatalysts with high-efficiency charge separation for solar-driven H2 production. [ABSTRACT FROM AUTHOR]

The spatiotemporal evolution of photogenerated charge carriers on surfaces and at interfaces of photoactive materials is an important issue for understanding fundamental physical processes in optoelectronic devices and advanced materials. Conventional optical probe-based microscopes that provide indirect information about the dynamic behavior of photogenerated carriers are inherently limited by their poor spatial resolution and large penetration depth. Herein, we develop an ultrafast scanning electron microscope (USEM) with a planar emitter. The photoelectrons per pulse in this USEM can be two orders of magnitude higher than that of a tip emitter, allowing the capture of high-resolution spatiotemporal images. We used the contrast change of the USEM to examine the dynamic nature of surface carriers in an InGaAs/InP avalanche photodiode (APD) after femtosecond laser excitation. It was observed that the photogenerated carriers showed notable longitudinal drift, lateral diffusion, and carrier recombination associated with the presence of photovoltaic potential at the surface. This work demonstrates an in situ multiphysics USEM platform with the capability to stroboscopically record carrier dynamics in space and time. [ABSTRACT FROM AUTHOR]

Carbon‐based hole transport material (HTM)‐free perovskite solar cells (CPSCs) are an innovative device architecture that mitigates inherent challenges associated with record‐breaking perovskite solar cells (PSCs), which rely on metal/HTMs, including instability, manufacturing intricacy, and elevated costs. The photovoltaic efficiency and stability of CPSCs are profoundly influenced by the charge carrier dynamics at the interfaces. Herein, the charge carrier dynamics at the carbon(C)–perovskite interface in CPSCs and its implications on photovoltaic performances and stability, an aspect that has received limited exploration thus far are probed, are investigated using transient surface photovoltage (Tr‐SPV) and transient photoluminescence measurements. The study reveals that the C‐electrode effectively acts as a selective barrier, impeding electrons while facilitating the extraction of holes at the C–perovskite interface. This selective blocking mechanism holds significant implications for improving the performance and stability of CPSCs over HTM‐free PSCs with gold(Au) electrodes. The stability of CPSCs is evaluated by measuring shelf life, maximum power point tracking, Tr‐SPV, and X‐Ray diffraction measurements. By delving into these pivotal aspects, this work aims to contribute to the advancement and understanding of CPSCs for sustainable and efficient energy conversion. [ABSTRACT FROM AUTHOR]

Novel Li/Al‐LDHs with high layer charges (HCLDHs) were synthesized in the light of the inter‐layer effect on Li+ adsorption. Compared with conventional low‐charge Li/Al‐LDHs (LCLDHs), HCLDHs exhibited a distinct micromorphology characterized by a preferential growth orientation along the c‐axis and a significantly reduced lateral diameter. Adsorption experiments showed that HCLDHs possessed superior Li+ adsorption performance in various brines, specifically with a Li+ adsorption capacity of 9.72 mg/g in Qarhan old brine, surpassing that of LCLDHs by 2 mg/g. All‐around characterizations and finite element analysis calculations uncovered that the reduced lateral dimensions facilitated the exposure of more accessible Li+ adsorption sites, while the high positive charge of the host layers decreased the electrostatic repulsion toward Li+ by attracting anions and increased the surrounding ionic strength. Surface photovoltage (SPV) and x‐ray absorption fine structure (XAFS) further proved the structural stability of HCLDHs, which ensured the maintenance of a high Li+ adsorption capacity during adsorption–desorption cycles. [ABSTRACT FROM AUTHOR]

Photocatalytic H 2 evolution requires excellent charge separation and fast surface electron injection, whereas it is difficult to achieve with a single semiconductor catalyst. Herein, we present a simple two-step hydrothermal method for coupling metalloid CoS 2 nanospheres with CaIn 2 S 4 micro-flowers, which exhibits a 6-fold increase in the photocatalytic hydrogen evolution rate as bare CaIn 2 S 4. This activity enhancement surpasses that of noble metal (Pt or AuCu) modified CaIn 2 S 4. During five runs of photocatalytic tests, the composite photocatalysts maintain high photostability, without significant changes in crystal structure or morphology. The charge transfer at CoS 2 /CaIn 2 S 4 interface is revealed by synchronous illumination X-ray photoelectron spectroscopy, surface photovoltage spectrum and DFT calculation. According to the mechanism study, it shows that metallic CoS 2 can act as electron traps to speed up electron transfer due to the formation of intimate CoS 2 /CaIn 2 S 4 heterojunctions, while at the same time CoS 2 can serve as active centers to catalytic the water reduction into H 2 molecules. Overall, we propose a simple route to modify a semiconductor photocatalyst that can result in multiple distinct effect including improved charge separation and injection efficiency. [Display omitted] • CoS 2 nanoparticles were deposited on the surface of CaIn 2 S 4 micro-flowers. • 5 wt% CoS 2 cocatalyst coupled with CaIn 2 S 4 shows the highest H 2 evolution rate (960 μmol g−1 h−1). • The AQE of the sample of 5 wt% CoS 2 /CaIn 2 S 4 reaches 3.2% at 480 nm. • Charge transfer process of CoS 2 /CaIn 2 S 4 was elucidated in detail. [ABSTRACT FROM AUTHOR]

[Display omitted] The growing concern over the rapid consumption of fossil fuels has spurred scientists to seek environment-friendly and sustainable energy alternatives. The utilization of photocatalytic water splitting shows great potential in generating environmentally friendly hydrogen energy. Zirconium-based porphyrin MOF-545 has drawn extensive attention in photocatalysis since it has strong light absorption and fast electron transfer capability. A series of Zr-based metalloporphyrins containing different metals, MOF-545M (M = Co, Ni, Cu, Zn), were synthesized and assembled with solid solution Zn x Cd 1-x S (ZCS) nanoparticle to develop the corresponding of hybrid photocatalysts, ZCS/MOF-545M. Various characterizations show that introducing the porphyrin MOF-545Co not only improve the visible light response range of Zn 0.5 Cd 0.5 S (ZCS-0.5) but also enhance the carrier separation efficiency of ZCS-0.5. The carrier transfer direction during the reaction was confirmed by surface photovoltage spectroscopy and shows the formation of S-scheme. Under visible light irradiation, the hybrid photocatalyst ZCS-0.5/MOF-545Co exhibits a high H 2 evolution rate of 148 μmol h−1, with increases of 52.8, 22.9 and 6.5 times than those of bare ZnS, CdS and ZCS-0.5, respectively. The present work gives a strategy for erecting S-scheme heterojunction to inhibit the photocorrosion of metal sulfides and enhancement the carrier separation efficiency. [ABSTRACT FROM AUTHOR]

Among the various photoanode materials investigated for photoelectrochemical water splitting cells, TiO2 stands out due to its abundance, stability, and favorable valence band edge for water oxidation. In this study, the importance of introducing and combining oxygen and titanium vacancy point defects in anatase TiO2 photoanodes to improve their performance is unveiled, achieving a photocurrent density of 0.73 (±0.015) mA cm−2 at +1.23 VRHE under 100 mW cm−2 of simulated sunlight or 26.4 mA cm−2 at +1.23 VRHE under 100 mW cm−2 of 365 nm light. The characterization by X‐ray photoelectron spectroscopy, surface photovoltage, and electron paramagnetic resonance demonstrates that these oxygen and titanium vacancies can have both collective and localized positive effects on the material, leading to a narrowing of the bandgap, an increase in donor density, and an increase in hydroxyl groups on the surface of TiO2. These result in enhanced light absorption, conductivity, and photovoltage, as well as a more negative flat‐band potential and increase in hole flux to the semiconductor–electrolyte interface. These findings provide valuable insights into the role of point defects in modulating the properties of TiO2 and have important implications for the development of high‐performance TiO2‐based devices. [ABSTRACT FROM AUTHOR]

The construction of interfacial electric field (IEF) in semiconductor heterojunction is of great significance in boosting photocatalytic hydrogen evolution through efficient separation of photogenerated charge‐carriers. However, the exploitation of IEF in type‐I heterojunction has not been proposed for designing photocatalysts. Herein, based on the density functional theory prediction, p‐SnS with different work functions modulated by Sn‐vacancy are compounded with n‐ZnIn2S4 containing S‐vacancy to form type‐I heterojunction. The optimized SnS/ZnIn2S4 photocatalyst without co‐catalysts exhibits an impressive hydrogen evolution rate of 22.75 mmol g−1 h−1, 6.23 times of ZnIn2S4. Systematic investigations reveal that the interfacial Sn‐S bond acts as a transport channel that accelerates the interface charge‐carriers transfer under the promotion of IEF originating from the significant Fermi level difference. A large difference in the surface photovoltage signal of SnS/ZnIn2S4 and ZnIn2S4 is achieved from effective photogenerated charge‐carriers separation by IEF. The new p‐n type‐I scheme of SnS/ZnIn2S4 induced by the interfacial mediation can separate the photogenerated charge‐carriers, and retain the highly reductive electrons of ZnIn2S4 for hydrogen evolution, overcoming the disadvantage of reduction potential decline in the typical type‐I scheme. This study will afford a new theoretical basis for the achievement of high‐efficiency photocatalytic hydrogen evolution through interface modulation. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate the potential of the contactless surface photovoltage (SPV) method for fast and reliable control of GaAs-based solar cells directly on epitaxial heterostructures before metallization and photolithography processes. The magnitude of the SPV corresponds to the generated photovoltage in the photoactive region, which is related to the open circuit voltage of the cell. The focus of this investigation is the potential of dilute nitride compounds grown by low-temperature liquid-phase epitaxy (LPE) for application as intermediate cells in multijunction solar cells. First, SPV spectroscopy is used to determine the photosensitivity spectral range and bandgap of the grown dilute nitride compound layers. Further, the photovoltaic quality of the grown solar cell heterostructures is evaluated by comparing the magnitude of their SPV signals with that of a reference GaAs solar cell. A drastic reduction in the measured SPV is observed for nitrogen-containing solar cell structures, which correlates with the lowering of solar cell open-circuit voltage values measured under standard test conditions. Finally, solar cell structures based on nitrogen-free GaAsSb compounds with the same long-wavelength photosensitivity limit as GaAsSbN are grown by LPE. They show one order of magnitude higher SPV signal and, therefore, have a great potential for solar cell application. [ABSTRACT FROM AUTHOR]

We present a new open-loop implementation of Kelvin probe force microscopy (KPFM) that provides access to the Fourier spectrum of the time-periodic surface electrostatic potential generated under optical (or electrical) pumping with an atomic force microscope. The modulus and phase coefficients are probed by exploiting a double heterodyne frequency mixing effect between the mechanical oscillation of the cantilever, modulated components of the time-periodic electrostatic potential at harmonic frequencies of the pump, and an ac bias modulation signal. Each harmonic can be selectively transferred to the second cantilever eigenmode. We show how phase coherent sideband generation and signal demodulation at the second eigenmode can be achieved by using two numerical lock-in amplifiers configured in cascade. Dual-heterodyne KPFM (DHe-KPFM) can be used to map any harmonic (amplitude/phase) of the time-periodic surface potential at a standard scanning speed. The Fourier spectrum (series of harmonics) can also be recorded in spectroscopic mode (DHe-KPFM spectroscopy), and 2D dynamic images can be acquired in data cube mode. The capabilities of DHe-KPFM in terms of time-resolved measurements, surface photovoltage (SPV) imaging, and detection of weak SPV signals are demonstrated through a series of experiments on difference surfaces: a reference substrate, a bulk organic photovoltaic heterojunction thin film, and an optoelectronic interface obtained by depositing caesium lead bromide perovskite nanosheets on a graphite surface. The conclusion provides perspectives for future improvements and applications.

Surface electric potential measurements are widely used in non-destructive inspection and testing of precision surfaces, for example, in the production of semiconductor devices and integrated circuits. Features of the construction and application of devices for measuring the surface electric potential using an immovable reference electrode are considered. Despite the need to increase the area of the probe compared to devices with a vibrating probe, measurement techniques with an immovable probe have a number of advantages and could expand the scope of surface electric potential measurements in the inspection of samples with precise surfaces. Models of the formation of a measuring signal in the presence of a spatial inhomogeneity of surface electric potential are presented and discussed.

Multilayer III–V-based solar cells are complex devices consisting of many layers and interfaces. The study and the comprehension of the mechanisms that take place at the interfaces is crucial for efficiency improvement. In this work, we apply frequency-modulated Kelvin probe force microscopy under ambient conditions to investigate the capability of this technique for the analysis of an InP/GaInAs(P) multilayer stack. KPFM reveals a strong dependence on the local doping concentration, allowing for the detection of the surface potential of layers with a resolution as low as 20 nm. The analysis of the surface potential allowed for the identification of space charge regions and, thus, the presence of several junctions along the stack. Furthermore, a contrast enhancement in the surface potential image was observed when KPFM was performed under illumination, which is analysed in terms of the reduction of surface band bending induced by surface defects by photogenerated carrier distributions. The analysis of the KPFM data was assisted by means of theoretical modelling simulating the energy bands profile and KPFM measurements.

Drawing inspiration from the enzyme nitrogenase in nature, researchers are increasingly delving into semiconductor photocatalytic nitrogen fixation due to its similar surface catalytic processes. Herein, we reported a facile and efficient approach to achieving the regulation of ZnO/ZnCr2O4 photocatalysts with ZnCr‐layered double hydroxide (ZnCr‐LDH) as precursors. By optimizing the composition ratio of Zn/Cr in ZnCr‐LDH to tune interfaces, we can achieve an enhanced nitrogen photofixation performance (an ammonia evolution rate of 31.7 μmol g−1 h−1 using pure water as a proton source) under ambient conditions. Further, photo‐electrochemical measurements and transient surface photovoltage spectroscopy revealed that the enhanced photocatalytic activity can be ascribed to the effective carrier separation efficiency, originating from the abundant composite interfaces. This work further demonstrated a promising and viable strategy for the synthesis of nanocomposite photocatalysts for nitrogen photofixation and other challenging photocatalytic reactions. [ABSTRACT FROM AUTHOR]

The loading of PDS improves the separation of photogenerated carriers, suppresses the bulk and surface recombination (including surface recombination of the back electron(BER)), and enhances the water oxidation kinetics, synthetically improves the PEC water oxidation performance [Display omitted] The kinetic competition between water oxidation/electron extraction processes and recombination behaviors is a key consideration in the development of efficient photoanodes for solar-driven water splitting. Investigating the photogenerated charge behaviors could guide the construction of high-efficiency photoanodes. In this study, the charge carrier kinetics involved in photoelectrochemical water oxidation of PDS/Ti-Fe 2 O 3 were analyzed using surface photovoltage (SPV), transient photovoltage (TPV), short-pulse transient photocurrent (TPC) and photoelectrochemical impedance spectra (PEIS). The TPC results indicate the interfacial electric field introduced by the PDS loading increases the electron extraction and suppresses the bulk recombination, enhancing the spatial separation of photogenerated charges, which is consistent with the SPV and TPV results. Besides, the surface recombination of the back electron (BER) is also attenuated, which enhances the long-lived holes at the surface of PDS/Ti-Fe 2 O 3 photoanode. Similarly, as obtained by PEIS fitting, the loading of PDS accelerates holes transfer at the photoanode/electrolyte interface, and increases the utilization of long-lived holes. In other word, the recombination behaviors of photogenerated charges are restrained both in the bulk and surface of the photoanode after the deposition of PDS, leading to enhanced PEC performance. These findings highlight the importance of understanding charge carrier dynamics in the design of high-efficient photoanodes. [ABSTRACT FROM AUTHOR]

Solvated electrons are highly reductive chemical species whose chemical properties remain largely unknown. Diamond materials are proposed as a promising emitter of solvated electrons and visible light excitation would enable solar‐driven CO2 or N2 reductions reactions in aqueous medium. But sub‐bandgap excitation remains challenging. In this work, the role of surface states on diamond materials for charge separation and emission in both gaseous and aqueous environments from deep UV to visible light excitation is elucidated. Four different X‐ray and UV–vis spectroscopy methods are applied to diamond materials with different surface termination, doping and crystallinity. Surface states are found to dominate sub‐bandgap charge transfer. However, the surface charge separation is drastically reduced for boron‐doped diamond due to a very high density of bulk defects. In a gaseous atmosphere, the oxidized diamond surface maintains a negative electron affinity, allowing charge emission, due to remaining hydrogenated and hydroxylated groups. In an aqueous electrolyte, a photocurrent for illumination down to 3.5 eV is observed for boron‐doped nanostructured diamond, independent of the surface termination. This study opens new perspectives on photo‐induced interfacial charge transfer processes from metal‐free semiconductors such as diamonds. [ABSTRACT FROM AUTHOR]

Constructing efficient polymer semiconductor/g‐C3N4 heterojunctions is highly desirable for enhancing the photogenerated charge separation of g‐C3N4 and further improving the solar‐hydrogen production efficiency. Herein, we synthesized poly(3‐thiophene boronic acid)/g‐C3N4 (PTBA/CN) heterojunctions with tight interface contact by a simple wet‐chemical strategy. The resulting ratio‐optimized 3PTBA/CN heterojunction exhibits 8.7 times enhancement of the visible‐light photocatalytic hydrogen production compared to CN. Based on the steady‐state surface photovoltage spectra (SS‐SPS), photoluminescence spectra (PL), ⋅OH amount measurements, time‐resolved photoluminescence spectra (TR‐PL), and single‐wavelength photocurrent action spectra, it is confirmed that the enhanced photocatalytic performance is mainly attributed to the promoted photogenerated charge separation resulting from the transfer of high‐level electrons from CN to PTBA via the formed tight interface contact, depending on the hydrogen bonding interactions between the boronic acid groups [−B(OH)2] of PTBA and the amino groups (−NH2) of CN. Furthermore, the −B(OH)2 of PTBA facilitates the uniform dispersion of the co‐catalyst Pt. This work provides an effective strategy for constructing efficient tightly connected polymer semiconductor/CN heterojunction photocatalysis. [ABSTRACT FROM AUTHOR]

A composite catalytic system using sulfur-vacancy-containing ZnIn2S4-Sv as a light-harvesting material and nickel-based polyoxometalate Na6K4[Ni4(H2O)2(PW9O34)2] (Ni4POM) as a co-catalyst was developed. The Ni4POM/ZnIn2S4-Sv composite gave a good hydrogen production rate of 337.5 μmol h−1, a value 11.8 times higher than that of ZnIn2S4-Sv. The direction of electron transfer, from ZnIn2S4-Sv to Ni4POM, was verified using surface photovoltage spectra. [ABSTRACT FROM AUTHOR]

Objective: A highly active and stable composite photocatalyst which can be used in practical environmental remediation was developed. Methods: g‐C3N4/SnO2/BiPO4 ternary composites (CN/SO/BPO) were synthesised via simple impregnation, and their texture structure, morphology, and surface composition were deeply characterized. Results: In just 25 min under visible‐light radiation, CN/SO/BPO almost eliminated rhodamine B, and the observed rate constant for the reaction was almost 36 and 3 times higher in comparison to that of CN/BPO and SO/BPO, respectively. Conclusions: On the basis of experimental outcomes and DFT calculation, the direct Z‐type structure of CN/SO/BPO lead to the improved photogenerated charge separation efficiency, as confirmed by surface photovoltage spectroscopy, electrochemical impedance spectroscopy, and transient photocurrent responses. [ABSTRACT FROM AUTHOR]

• Surface photovoltage of n -Bi 2 WO 6 is enhanced by increasing crystal plane orientation ratio of (2 0 0)/(1 1 3) due to higher hole mobility of (2 0 0) crystal plane. • Hydrothermal synthesis and post-heating could be adopted to adjust the crystal plane orientation ratio for enhancing the surface photovoltage. • Surface photovoltaic spectrum could be used to explore the surface charge transfer mechanism of photovoltaic materials. Enhancing photoelectric sensitivity of semiconductors is meaningful to develop novel photoelectric materials but still challenging for a pristine semiconductor. Here we increase the crystal plane orientation ratio for higher hole mobility to enhance the surface photovoltage of n -type Bi 2 WO 6 depending on the anisotropy of hole mobility. A strategy of hydrothermal synthesis and post-heating is adopted to prepare Bi 2 WO 6. The diffraction peak relative intensity of (2 0 0) crystal plane in Bi 2 WO 6 increases with the post-heating temperature from 200 to 400 °C and then decreases. The surface photovoltage of nano-sheet Bi 2 WO 6 is enhanced to the maximum and then decreased with the diffraction peak change of (2 0 0) crystal plane. Theory calculation shows the hole effective mass of the crystal with (2 0 0) crystal plane is smaller than that of (1 1 3), indicating the higher hole mobility in (2 0 0) plane which contributes to the enhanced photovoltaic response. The investigation paves a way to enhance the photovoltaic properties of semiconductors by increasing the hole mobility depending on surface photovoltaic technology facilely. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN) nanowire arrays on silicon are able to drive the overall water-splitting reaction with up to 3.3% solar-to-hydrogen efficiency. Photochemical charge separation is key to the operation of these devices, but details are difficult to observe experimentally because of the number of components and interfaces. Here, we use surface photovoltage spectroscopy to study charge transfer in i-, n-, and p-GaN nanowire arrays on n+-Si wafers in the presence and absence of Rh/Cr2O3 co-catalysts. The effect of the space charge layer and sub-bandgap defects on majority and minority carrier transport can be clearly observed, and estimates of the built-in potential of the junctions can be made. Transient illumination of the p-GaN/n+-Si junction generates up to −1.4 V surface photovoltage by carrier separation along the GaN nanowire axis. This process is central to the overall water-splitting function of the n+-Si/p-GaN/Rh/Cr2O3 nanowire array. These results improve our understanding of photochemical charge transfer and separation in group III–V semiconductor nanostructures for the conversion of solar energy into fuels. [ABSTRACT FROM AUTHOR]

Integrated photoelectrochemical devices rely on the synergy between components to efficiently generate sustainable fuels from sunlight. The micro- and/or nanoscale characteristics of the components and their interfaces often control critical processes of the device, such as charge-carrier generation, electron and ion transport, surface potentials, and electrocatalysis. Understanding the spatial properties and structure–property relationships of these components can provide insight into designing scalable and efficient solar fuel components and systems. These processes can be probed ex situ or in situ with nanometer-scale spatial resolution using emerging scanning-probe techniques based on atomic force microscopy (AFM). In this Perspective, we summarize recent developments of AFM-based techniques relevant to solar fuel research. We review recent progress in AFM for (1) steady-state and dynamic light-induced surface photovoltage measurements; (2) nanoelectrical conductive measurements to resolve charge-carrier heterogeneity and junction energetics; (3) operando investigations of morphological changes, as well as surface electrochemical potentials, currents, and photovoltages in liquids. Opportunities for research include: (1) control of ambient conditions for performing AFM measurements; (2) in situ visualization of corrosion and morphological evolution of electrodes; (3) operando AFM techniques to allow nanoscale mapping of local catalytic activities and photo-induced currents and potentials. [ABSTRACT FROM AUTHOR]

III-nitrides have revolutionized lighting technology and power electronics. Expanding the nitride semiconductor family to include heterovalent ternary nitrides opens up new and exciting opportunities for device design that may help overcome some of the limitations of the binary nitrides. However, the more complex cation sublattice also gives rise to new interactions with both native point defects and defect complexes that can introduce disorder on the cation sublattice. Here, depth-resolved cathodoluminescence spectroscopy and surface photovoltage spectroscopy measurements of defect energy levels in ZnGeN2 combined with transmission electron microscopy and x-ray diffraction reveal optical signatures of mid-gap states that can be associated with cation sublattice disorder. The energies of these characteristic optical signatures in ZnGeN2 thin films grown by metal–organic chemical vapor deposition are in good agreement with multiple, closely spaced band-like defect levels predicted by density functional theory. We correlated spatially resolved optical and atomic composition measurements using spatially resolved x-ray photoelectron spectroscopy with systematically varied growth conditions on the same ZnGeN2 films. The resultant elemental maps vs defect spectral energies and intensities suggest that cation antisite complexes (ZnGe–GeZn) form preferentially vs isolated native point defects and introduce a mid-gap band of defect levels that dominate electron–hole pair recombination. Complexing of ZnGe and GeZn antisites manifests as disorder in the cation sub-lattice and leads to the formation of wurtzitic ZnGeN2 as indicated by transmission electron microscopy diffraction patterns and x-ray diffraction reciprocal space maps. These findings emphasize the importance of growth and processing conditions to control cation place exchange. [ABSTRACT FROM AUTHOR]

The performance of five hole‐transporting layers (HTLs) is investigated in both single‐junction perovskite and Cu(In, Ga)Se2 (CIGSe)‐perovskite tandem solar cells: nickel oxide (NiOx,), copper‐doped nickel oxide (NiOx:Cu), NiOx+SAM, NiOx:Cu+SAM, and SAM, where SAM is the [2‐(3,‐6Dimethoxy‐9H‐carbazol‐9yl)ethyl]phosphonic acid (MeO‐2PACz) self‐assembled monolayer. The performance of the devices is correlated to the charge‐carrier dynamics at the HTL/perovskite interface and the limiting factors of these HTLs are analyzed by performing time‐resolved and absolute photoluminescence ((Tr)PL), transient surface photovoltage (tr‐SPV), and X‐ray/UV photoemission spectroscopy (XPS/UPS) measurements on indium tin oxide (ITO)/HTL/perovskite and CIGSe/HTL/perovskite stacks. A high quasi‐Fermi level splitting to open‐circuit (QFLS‐Voc) deficit is detected for the NiOx‐based devices, attributed to electron trapping and poor hole extraction at the NiOx‐perovskite interface and a low carrier effective lifetime in the bulk of the perovskite. Simultaneously, doping the NiOx with 2% Cu and passivating its surface with MeO‐2PACz suppresses the electron trapping, enhances the holes extraction, reduces the non‐radiative interfacial recombination, and improves the band alignment. Due to this superior interfacial charge‐carrier dynamics, NiOx:Cu+SAM is found to be the most suitable HTL for the monolithic CIGSe‐perovskite tandem devices, enabling a power‐conversion efficiency (PCE) of 23.4%, Voc of 1.72V, and a fill factor (FF) of 71%, while the remaining four HTLs suffer from prominent Voc and FF losses. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are considered as excellent candidate materials for light-emitting diode (LED)-based lighting and display applications due to their excellent optical properties. However, the intrinsic unstable properties of QDs under external environments or the incompatibility between QDs and polymer composites hindered the QD-related applications. Herein, a universal modification method based on the optimization of QDs was developed for device applications. The highly dispersible and photostable QDs/siloxane composite was constructed by using the dual silica-encapsulated strategy of core/multishell CdSe/CdS/ZnCdS QDs to improve the performance of QDs. First, core/multishell QD's size and components were optimized to enhance stability. Then, QDs@SiO2-OTMS was prepared by a combination of the reverse micro-emulsion method and surface modification. Such a double silica surface modification strategy is found to be very effective in improving the dispersion by matching the surface energy of QDs@SiO2-OTMS with that of siloxane resins. The as-prepared QDs@SiO2-OTMS/siloxane films had long-term (10 days) stability against heat and moisture and corrosive solution (HCl and NaOH). For the first time, the surface photovoltage (SPV) technique was used to study the in situ thermal stability of QDs@SiO2-OTMS, and it was found that surface defects were greatly suppressed at high temperatures. Taking these advantages, a white LED (WLED) with a color coordinate of (0.336, 0.325), color temperature of 5287 K, color gamut 123% National Television Systems Committee (NTSC,1931), and long-time stability at 20 mA had been fabricated by integrating green and red QDs@SiO2-OTMS/siloxane. These results make QDs@SiO2-OTMS/siloxane excellent candidates for QD lighting and display applications. [ABSTRACT FROM AUTHOR]