Donor Density Research Articles

Performance optimization of lead-free potassium germanium halide based perovskite solar cells: A numerical study

Conventional lead-halide perovskite solar cells (PSCs) have great potential as top contenders for commercial utilization due to their impressive performance. Nevertheless, the stability issues and undue toxicity have limited their widespread use. Consequently, lead-free germanium-based PSCs have materialized as potential substitutes due to their high working efficiency and exceptional sustainability. The current study has examined various configurations of non-toxic inorganic potassium germanium trichloride (KGeCl3) based PSC structure by using different Hole Transport Layers (HTL) and Electron Transport Layers (ETLs) respectively. This work proposes an efficient Ge-based PSC (structure; FTO/MoO3/KGeCl3/WS2/Au), which has been optimized theoretically using SCAPS-1D. The influence of the material parameters, such as the thickness of the absorber layer (nm), donor density (Nd), acceptor density (Na), absorber defect density(Nt), interface layer defect density (IL1& IL2), series resistance (Rs) and shunt resistance (Rsh), and working temperature (K), has been optimized. The open circuit voltage (Voc), current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) of KGeCl3-based PSC have all been commendably optimized. The results indicated WS2 as the most effective ETL for KGeCl3 with MoO3 as an HTL, yielding notable cell performance with Voc of 0.88 V, Jsc of 41.45 mA/cm2, FF of 81.76 %, and PCE of 29.83 %. The outcomes of this simulation study suggest the utilization of KGeCl3 as the absorber layer, in conjunction with WS2 and MoO3 as advanced ETL and HTL layers, which pays the way for continued development and optimization of Ge-based PSCs for potential applications.

Photoelectrocatalytic efficiency of In2S3–In2O3 films as photoelectrodes/photocatalyst in hydrogen production reaction

In2S3–In2O3 films were used as photoelectrodes and photocatalysts for hydrogen production. The films were grown using a hydrothermal method for different reaction times (4, 6, 8, 12, 18 and 24h). The difference in the reaction time influences the presence of other crystalline phases, such as β-In2S3, In2O3, Ti3S4, and Ti5S8, on the film structure; the presence of these elements was verified by the XPS results. Furthermore, the mixture of phases generates different morphologies such as flowers, pyramids, and sheets. The best photoelectrochemical results were obtained from the films deposited at a reaction time of 6, 8, and 12 h, as these films have an OCP value of ∼0.3586, 0.3791 and 0.4771 VRHE and a photocurrent density of 3, 1.92, and 1.5 μA•cm−2 at 1.23 V vs. RHE, respectively. According to these results, the 12h/In2S3–In2O3 film has the highest donor density and the lowest Debye length, which enhances the efficiency of photogenerated electrons and electron-hole separation. Moreover, the highest photocatalytic hydrogen production was achieved with the 12h/In2S3–In2O3 film, which, in addition to presenting the most optimal photoelectrochemical properties, also has defects such as oxygen deficiencies, Ini and VIn, which could act as traps for electrons in the recombination process, increasing the reduction reactions at low energy and enhancing hydrogen production.

Porous-anodic-alumina-templated Ta-Nb-alloy/oxide coatings via the magnetron-sputtering/anodizing as novel 3D nanostructured electrodes for energy-storage applications

The Ta-52 at.%Nb thin alloy films were magnetron sputter-deposited over a low-aspect-ratio nanoporous anodic-alumina template formed in 0.05 M tartaric acid solution at 250 V and modified by the pore-widening technique to enlarge the pores up to ∼500 nm. The alloy coated the pores evenly, thus forming a 3D continuous conducting nanofilm on the template. Partially anodizing the templated alloy in a borate buffer solution of pH 7.5 generated a compact amorphous mixed-oxide anodic film thickening proportionally to the applied voltage. It was revealed that the oxide on the Ta-52 at.%Nb alloy grows with a slower migration of Ta5+ ions relative to Nb5+ ions, resulting in mixing Ta2O5 and Nb2O5 in the film depth and forming a few-nm-thick Nb2O5 outmost layer. The unique migration of Ta4+, Ta3+, Nb4+, and Nb3+ ions is assumed accountable for forming corresponding suboxides in the 3D anodic film in contrast to a flat Ta-52 at.%Nb alloy film used as a reference. The 3D anodic films behave as an n-type semiconductor with a low donor density Nd = ∼2 × 1018 cm−3, appropriate for dielectric applications. An unusual two-layered structure with a sharp electrical interface revealed in the 3D oxide films anodized to 30–130 V, comprising a low-resistivity layer superimposed on the high-resistivity layer, is explained by an immobile negative space charge in the outer film part. The air-annealing at moderate temperatures releases the space charge and transforms the two layers into a high-resistivity single layer having substantially improved dielectric properties and thermostable (up to 250 °C) capacitance of 1.2 μF cm−2 achieved for the film anodized to practical 50 V. The 3D films having up to 4.5 times enlarged effective surface area can be utilized as novel metal/oxide nanostructured electrodes for electrolytic microcapacitors suitable for classical electronic circuits and energy-storage applications.

Structures, electrochemical properties and corrosion mechanisms of TiAlCr(C)N/TiAlN/TiN coatings by DFT calculations

Element additions in ceramic coatings played a positive role in electrochemical corrosion process, and Cr and C were doped into TiAlN coating by cathode arc ion plating. The effects of Cr and C additions on the structures and electrochemical properties of TiAlN coatings in 3.5 % NaCl solution were comparatively investigated, and the corrosion mechanisms were discussed with the density functional theory calculation. The results show that the particle size of TiAlCrN/and TiAlCN/TiAlN/TiN coatings are 31.6 and 25.7 nm, respectively, and the corresponding bonding strength is 16.18 and 37.93 N, respectively. The corrosion resistance of TiAlCrN/TiAlN/TiN coating is higher compared with the TiAlCN/TiAlN/TiN coating, which is attributed to the stronger oxidation reactions of TiAlCrN/TiAlN/TiN coating. The donor density of passive film on the TiAlCrN/TiAlN/TiN coating is lower than that on the TiAlCN/TiAlN/TiN coating, showing the minor susceptibility of TiAlCrN/TiAlN/TiN coating to corrosion. Moreover, the band gap and DOS of Cr2N and Cr2O3 on the TiAlCrN/TiAlN/TiN coating are larger than those of Al3C4 on the TiAlCN/TiAlN/TiN coating, presenting the stronger corrosion resistance.

Efficiency enhancement above 31 % of Sb2Se3 solar cells with optimizing various BSF layer

Recent advancements in solar technology have increased the acceptance of antimony selenide (Sb2Se3) due to its advantageous properties. This study aims to enhance the performance of the Sb2Se3 structure by using tungsten disulfide (WS2) as the window layer and copper zinc tin selenide (CZTSe) as the back surface field (BSF) layer, utilizing SCAPS-1D (solar cell and capacitance simulator). An initial investigation of seven potential BSF layers identified CZTSe as the best choice for improving power conversion efficiency (PCE). By carefully simulating various parameters, including the thicknesses of the absorber and window layers, donor and acceptor densities, defect density, shunt resistance, and series resistance, significant performance improvements were achieved. Without the BSF layer, the cell showed a PCE of 28.20 % along with specific values for short circuit current density (JSC), open-circuit voltage (VOC), and fill factor (FF). The addition of the BSF layer increased the PCE to 31.52 %, along with enhancements in JSC, VOC, and FF. These results highlight the potential of this approach for developing high-performance Sb2Se3 based solar cells, surpassing conventional designs.

Ferromagnetic semiconductor EuO thin films characterized by vacuum electrochemical process with ionic liquid

In this study, the electrochemical impedance analysis was demonstrated for thin film EuO, a ferromagnetic semiconductor, by taking the advantage of our original instrument, which enables to perform the entire process from thin film deposition to electrochemical measurement with ionic liquid in a vacuum. Effects of whether surface protecting layers were insulative or metallic, as well as their thickness on the electrochemical measurement of EuO thin films were examined by comparing the choices of amorphous alumina and Ag metal as the protecting layer. As a result, the relative permittivity of EuO films, even with a thickness of 2 nm, was successfully estimated and the averaged value was 6.6 within an error of 10 %. Furthermore, the donor density accordingly estimated was found well correlated with the Curie temperature TC of the EuO films.

Synergistic Enhancement of Water-Splitting Performance Using MOF-Derived Ceria-Modified g-C3N4 Nanocomposites: Synthesis, Performance Evaluation, and Stability Prediction with Machine Learning.

Diminishing the charge recombination rate by improving the photoelectrochemical (PEC) performance of graphitic carbon nitride (g-C3N4) is essential for better water oxidation. In this concern, this research explores the competent approach to enhance the PEC performance of g-C3N4 nanosheets (NSs), creating their nanocomposites (NCs) with metal-organic framework (MOF)-derived porous CeO2 nanobars (NBs) along with ZnO nanorods (NRs) and TiO2 nanoparticles (NPs). The synthesis involved preparing CeO2 NBs and g-C3N4 NSs through the calcination of respective precursors, while the sol-gel method is employed for ZnO NRs and TiO2 NPs. Following the subsequent analysis of the physicochemical properties of the materials, the binder-free brush-coating method is deployed to fabricate NC-based photoanodes, followed by an evaluation of the PEC performance through various electrochemical techniques. Remarkably, the binary g-C3N4/CeO2 NCs with 20 wt % CeO2 NBs (gC20 NCs) exhibited a significantly enhanced current density of 0.460 mA/cm2 at 1.23 V vs reversible hydrogen electrode, which is 2.3 times greater than that of bare g-C3N4 NSs (0.195 mA/cm2). Further improvements are observed with ternary gC20/TiO2 (gCT50) and gC20/ZnO (gCZ50) NCs, achieving current densities of 1.810 and 1.440 mA/cm2, respectively. These enhanced current densities are attributed to increased donor densities, reduced charge transfer resistances, and efficient charge transport within the NCs. In addition, higher surface areas with beneficial instinctive defects are perceived for gCT50 and gCZ50 NCs, as revealed by Brunauer-Emmett-Teller and electron spin resonance analysis. Finally, the stability of gCZ50 and gCT50 NC-based photoanodes is predicted and forecasted with the help of the recurrent neural network-based long short-term memory technique. Overall, this study demonstrates the efficacy of organic-inorganic hybrids for efficient photoanodes, facilitating advancements in water-splitting studies.

Study on the repair behavior of passive film of iron-based amorphous coatings by eco-friendly phosphate inhibitors

The passivation ability of the coating can be improved by adjusting the elements proportion in the Iron-based Amorphous Coating and the spraying process, but the process is complicated and costly. In this study, it was found for the first time that Iron-based Amorphous Coatings can quickly form passive films in phosphate atmosphere, which simplifies the coating strengthening process. Electrochemical measurements, XPS, AFM, FTIR, and SEM-EDS were used to investigate the inhibition mechanism of eco-friendly phosphates on the dynamic dissolution of passive film of Fe-based amorphous coating. When the coating was soaked in 3.5 wt% NaCl + 0.1 M solution, the iron phosphate compound on the coating surface promoted the repair and growth of the passive film, and the film thickness increased by more than 32.9 %. The increase of Fe2+/Fe3+ and (O2-+H2O)/OH- in the passive film means that more insoluble Fe-Cr compound growth significantly reduces the donor density (Nd) in the passive film and inhibits the degradation rate of the passive film in the corrosive environment.

Current status of Pb-free PSCs and infer the highest achievable PCE via numerical modeling, and optimization of novel structure FAMASnGeI3 based PSCs

In this study, we have extensively investigated an eco-friendly perovskite-based solar cell via a theoretical approach and numerical simulation. For that purpose, firstly, we have conducted a brief literature review to decipher the status of Pb-free perovskite solar cells (PSCs). The literature review reflects that the research on Pb-free PSCs is going on with immense interest. By acquiring inspiration from the literature review, we have designed a Pb-free hybrid PSC with a structure of FTO/CdS/FAMASnGeI3/NiO/Ag utilizing SCAPS-1D software. The structure has been optimized by fine-tuning the thickness, and defect density of the light-absorbing layer and the thickness, donor density, and band gap of ETL. The optimized structure of Pb-free perovskite material displays promising results with PCE of 30.05 %, Voc of 0.964 V, fill factor of 82.35%, and current density of 27.77 mA cm−2. In addition, we have also found that the temperature and light intensity play a crucial role in the performance of the proposed PSC. We have found quantum efficiency as high as 98% for 360 nm thickness of the perovskite absorber layer. Finally, from the dark J–V analysis, lower current density (6.73×10−8 mA cm−2), less series resistance (2.8×10−5 Ωcm2) as well as high shunt resistance (11412.67 Ωcm2) were witnessed, which is expectable for a promising solar cell. Our inclusive exploration unveiled the fact that the suggested novel architecture (FTO/CdS/FAMASnGeI3/NiO/Ag) can be considered an exceptional design for PSCs with greater efficiency and practical suitability.

An extensive study on charge transport layers to design and optimization of high-efficiency lead-free Cs2PtI6-based double-perovskite solar cells: A numerical simulation approach

Perovskite materials are getting attention day by day due to their numerous optoelectronic properties. Lead-free perovskites are well-known for various applications in photovoltaic devices due to their non-toxicity which has no impacts on both the environment and health. Cs2PtI6, a lead-free halide perovskite, is renowned for its broad-spectrum light absorption and remarkably high absorption coefficient. Its stability under ambient conditions surpasses that of numerous other halide perovskites, rendering it exceptionally appealing for photovoltaic applications. The device configuration with FTO/ETL/Cs2PtI6/HTL/Au is used in this study where 4 different ETLs and 10 HTLs are used to investigate the best device configuration. The impact of different device parameters like thickness, acceptor density, donor density, and defect density are optimized to attain the best efficient device configuration. SCAPS-1D simulator is used to perform numerical analysis under light intensity of AM 1.5 light spectrum (100 mW/cm2). After the optimization of different device parameters, the device configured with FTO/SnS2/Cs2PtI6/MoTe2/Au shows the best performance among four devices where PCE is 32.98 %, VOC is 1.11 V, JSC is 33.19 mA/cm2, FF is 88.89 %. This suggested Cs2PtI6-based perovskite solar cells demonstrate superior performance compared to numerous lead perovskite-based solar cells, highlighting Cs2PtI6 as a promising alternative for photovoltaic applications while mitigating toxicity concerns.

Investigating the influence of oxygen doping in modulating product distribution for electrocatalytic CO2 reduction reaction

Efficient carbon recycling hinges on a comprehensive understanding of the mechanics behind electrocatalytic carbon dioxide reduction reactions (ECO2RR). Here, we have engineered, in-situ growth of CuO featured on O-doped gCN (COG) and ex-situ growth of CuO on bare gCN (CG) respectively, functioned as platforms fordisengaging the fundamental of ECO2RR. The COG holds substantial capacity compared to CG for efficient conversion of CO2 into hydrocarbons and initiated the C2 product pathway with enlarged faradaic efficiency (FE). The experimental results indicate that the COG enhanced the product conversion of CH3OH (FE = 61.5% ± 0.5), C2H5OH (FE = 24.7% ± 0.5), and HCOO– (FE = 6.1% ± 0.5) at −1.1 V Vs RHE. Meanwhile, the CG exhibited the maximum conversion of CO2 into CH3OH (FE = 56.4% ± 0.5) at the same potential range. For the CG, the partial current density of CH3OH (JCH3OH) is −1.8 mA cm−2, whereas COG exhibited −4.9 mA cm−2. Interestingly, in this ECO2RR, the study of oxygen doping demonstrated that feasible CO2 conversion, due to its affinity towards CO2 and high donor density.

Unveiling the potential of lead-free Cs2AgBi0.75Sb0.25Br6 double perovskite solar cells with multilayer charge transport for 30% efficiency

The present study delves into the utilization of computer modeling techniques to analyze a photovoltaic (PV) design incorporating a lead (Pb)-free perovskite absorber material. This innovative structure employs a cesium-based double perovskite material, specifically Cs2AgBi0.75Sb0.25Br6, characterized by an energy bandgap of 1.80 eV. The Cs2AgBi0.75Sb0.25Br6 exhibits a range of advantageous properties, including heightened stability in ambient conditions and appropriately aligned bandgaps. Given these considerations, an extensive exploration of the FTO/CdS/Cs2AgBi0.75Sb0.25Br6 /HTL/Au configuration was undertaken to assess the impact of ten distinct hole transport layers (HTLs) on the solar cell's efficiency. The simulation and analysis of all devices were conducted employing the one-dimensional SCAPS-1D (Solar Cell Capacitance Simulator) tool. Furthermore, the efficiency of the FTO/ETL/Cs2AgBi0.75Sb0.25Br6 /MoO3/Au architecture was probed, employing six different electron transport layers (ETLs) (BaSnO3, PC61BM, SnS2, Ti2O3:Nb, CdS, ZnOS), to discern the optimal combination. Post-optimization, adjustments were made to the absorber and ETL thickness, as well as the acceptor doping and defect density of the absorber, and the donor and defect density of the ETL, for the six combinations assessed. These topologies were also examined for their impacts on series and shunt resistance, capacitance, the Mott-Schottky effect, generation and recombination processes, current–voltage density, and quantum efficiency. Eventually, the most efficient cell in this study achieved a power conversion efficiency (PCE) of 30.30 % and featured the FTO/ZnOS/Cs2AgBi0.75Sb0.25Br6/MoO3/Au configuration. The aforementioned findings hold significant potential for advancing lead-free, double perovskite solar cells (PSCs) that are both more efficient and environmentally sustainable, paving the way for their widespread adoption in the future.

Improved photoelectrochemical performance of tungsten-catalyzed graphene nanoplatelet electrodes prepared by hot-wire chemical vapor deposition at low substrate temperatures

The current increase in demand for graphene in various energy applications such as electrode materials for supercapacitors, batteries, thermoelectric, and hydrogen production via water-splitting, the production of high-quality graphene, considering its fascinating physical and electrical properties, high-yield, and large-area has becoming more challenging at the research and development level. Therefore, in this work, graphene nanoplatelets (GNPs) were directly grown on tungsten nanoparticle (W NP)-coated p-type crystalline silicon and quartz substrates using hot-wire chemical vapor deposition at low substrate temperatures (<500 °C). Prior to the GNP deposition, a plasma process was employed to induce the formation of W NPs, which act as a metal catalyst for facilitating the growth of large-area and multi-layer GNPs. The W NPs were formed at substrate temperatures ranging from 250 to 550 °C, with the largest graphene sheet was grown at 450 °C. Higher substrate temperatures promote the growth of high-quality graphene layers with high intensities of G (IG) and 2D bands (I2D), and high I2D/IG ratio values. The GNP photoelectrode prepared at 450 °C demonstrated better photoelectrochemical responses with the highest photocurrent density of 1.65 mA/cm2 at 1.5 VAg/AgCl, the lowest charge transfer resistance (14.0 kΩ), and the highest donor density (2.57 × 10 28 cm−3) compared to the tungsten carbide thin film and W NP electrodes prepared at the same temperature. The effects of substrate temperature on the optical, structural, and photoelectrochemical properties of the as-grown GNPs are discussed.

Comparing Electrochemical Passivation and Surface Film Chemistry of 654SMO Stainless Steel and C276 Alloy in Simulated Flue Gas Desulfurization Condensates.

This research examines the behavior of electrochemical passivation and the chemistry of surface films on 654SMO super austenitic stainless steel and C276 nickel-based alloy in simulated condensates from flue gas desulfurization in power plant chimneys. The findings indicate that the resistance to polarization of the protective film on both materials initially rises and then falls with either time spent in the solution or the potential of anodic polarization. Comparatively, 654SMO exhibits greater polarization resistance than C276, indicating its potential suitability as a chimney lining material. Mott-Schottky analysis demonstrates that the density of donors in the passive film formed on 654SMO exceeds that on C276, potentially due to the abundance of Fe oxide in the passive film, which exhibits the characteristics of an n-type semiconductor. The primary components of the passive films on both materials are Fe oxides and Cr oxides. The formation of a thin passive film on C276 in the simulated condensates is a result of the low Gibbs free energy of nickel oxide and low Cr content. The slower diffusion coefficient of point defects leads to the development of a thicker and more compact passive film on the surface of 654SMO.

Numerical optimization of interface engineering parameters for a highly efficient HTL-free perovskite solar cell

Decarbonizing the world’s energy system has set the stage in favor of renewable energy alternatives such as the more reliable, abundant, inexhaustible, and sustainable solar energy. However, the photovoltaic technology faces significant stability, longevity, and scalability challenges. These difficulties can be overcome by judicious optimization of interfacial engineering of the solar cell architecture that will decrease the cost of fabrication and enhance the solar cell performance and durability. Herein, a comprehensive analysis of a novel high-performance hole transport layer-free (HTL-free) perovskite solar cell (PSC) of the configuration, ITO/PC61BM/CH3NH3SnI3/Pt, was investigated by device simulation while optimizing electron transport materials, metal back contacts, front contact materials, and buffer layers. The focus is on enhancing device performance by introducing various types of buffer layers, such as cadmium sulphide (CdS) in the proposed solar cell model. By fine-tuning the ETL layers and manipulating perovskite acceptor and donor densities, better device performance was achieved. Furthermore, the Mott-Schottky capacitance analysis yielded critical insights into the interface properties and dynamics of charge carriers within the solar cell structure. Optimizing back contacts also play a critical role in charge extraction and reduced recombination losses. Leveraging a sophisticated simulation platform, SCAPS-1D, the study assesses how design strategies impact photovoltaic electrical outcomes such as open-circuit voltage (Voc), power conversion efficiency (PCE), short-circuit current density (Jsc), and Fill factor (FF). The proposed HTL-free device posted remarkable results – PCE of 38.11 %, Jsc of 35.32 mAcm−2, FF of 88.67 %, and Voc of 1.2168 V. Accordingly, this work inspires the promising prospects of HTL-free PSCs in achieving robust solar harvesting capabilities while streamlining device affordability. Therefore, the proposed device architecture stimulates the journey towards affordable and high-performance scalable solar cell modules.

Unraveling the effects of nano-grained microstructure on mechanical behavior, corrosion, and in vitro biocompatibility of 316L austenitic stainless steel

Nanograins are often beneficial in achieving better cytocompatibility for metallic implants. In this work, we have achieved grains from the micro to nano range in 316L austenitic stainless steel by a combination of cryo-rolling (50%, 70%, and 90% thickness reduction) followed by annealing (750–1000 °C for 2–20 min). The combined effect of grain refinement along with texture on its mechanical, corrosion, and in vitro cellular behavior was thoroughly investigated. Microstructural observations revealed nanograins formation (grain size = 144 nm) only for the 90CRA sample, whereas grain refinement in the micron range was observed for 0-70CRA samples. Electron backscatter diffraction (EBSD) studies showed fully austenitic structures for all the annealed samples while low Kernel Average Misorientation (KAM) values indicated strain-free microstructures. Orientation distribution function (ODF) maps showed the presence of strong γ-fiber (<111>||ND) and weak α-fiber (<110>||ND) in the 90CRA sample. The grain refinement led to an increase in the yield strength and ultimate tensile strength from 470.6 ± 16.21 MPa and 858.35 ± 31.82 MPa (0CRA) to 1662.06 ± 58.44 MPa and 2112.3 ± 51.62 MPa (90CRA), respectively. The potentiodynamic polarization study revealed that the corrosion rate of the 90CRA sample was about eight times less than that of the 0CRA sample. This was further corroborated by Mott-Schottky analysis, which showed a lowering of both acceptor and donor densities with the reduction in grain size. The evolution of a strong <111> texture during cryo-rolling contributed towards enhanced corrosion resistance of nano-grained 316L. Furthermore, grain refinement improved wettability, which in turn led to better cell proliferation and differentiation. At all culture days, MC3T3-E1 cell proliferation and differentiation were considerably higher for nano-grained 316L micron-sized counterparts. Thus, grain refinement to the nano range is an effective technique for the property enhancement of biomedical implants.

Crafting defective ZnO nanoparticles: A green synthesis for enhanced photocatalytic degradation of organic pollutants

Surface defect engineering is a promising strategy for enhancing the number of surface-active sites to facilitate efficient redox reactions that occur on the surface of a photocatalyst. A green approach was employed to prepare urea- and choline-chloride-based deep eutectic solvent (DES) for the synthesis of ZnO/Zn(OH)2 supported by a DES complex (Zn precursor). Surface defects on ZnO nanoparticles (NPs) were tailored by decomposing the Zn precursor in air. In addition, calcination improved the crystallinity and surface-active sites of the defective ZnO by creating surface oxygen vacancies (Vo). The appearance of an Electron paramagnetic resonance peak at a g value of 1.96 confirms the formation of single-charged Vo defects on the surface of ZnO. The photocatalyst prepared at a reaction bath temperature of 75 °C (Vo-ZnO-75) showed the highest photocatalytic activity. The observed green emission in the photoluminescence spectrum and X-ray photoelectron spectroscopy analysis suggests the formation of defects on the ZnO surface. Consequently, Vo-ZnO-75 enhanced surface donor density (14.4×1020 cm−3) and lower charge transfer resistance (88.89 × 103 Ω). The optimized photocatalyst of Vo-ZnO-75 has 94% removal efficiency for rhodamine B degradation within 60 min. This study sheds new light on the development of an efficient and eco-friendly approach for preparing defective ZnO NPs for photocatalytic applications.

Fine-Tuning the Photocatalytic Activity of the Anatase {1 0 1} Facet through Dopant-Controlled Reduction of the Spontaneously Present Donor State Density.

The present study highlights the importance of the net density of charge carriers at the ground state on photocatalytic activity of the faceted particles, which can be seen as a highly underexplored problem. To investigate it in detail, we have systematically doped {1 0 1} enclosed anatase nanoparticles with Gd3+ ions to manipulate the charge carrier concentration. Furthermore, control experiments using an analogical Nb5+ doped sample were performed to discuss photocatalytic activity in the increased range of free electrons. Overall results showed significant enhancement of phenol degradation rate and coumarin hydroxylation, together with an increase of the designed Gd/Ti ratio up to 0.5 at. %. Simultaneously, the mineralization efficiency, measured as a TOC reduction, was controlled between the samples. The observed activity enhancement is connected with the controlled decrease of the donor state density within the materials, being the net effect of the spontaneously present defects and introduced dopants, witch reduce hydroxylation and the hole trapping ability of the {1 0 1} facets. This allows to fine-tune multi-/single-electron processes occurring over the prepared samples, leading to clear activity maxima for 4-nitrophenol reduction, H2O2 generation, and ·OH formation observed for different donor densities. The optimized material exceeds the activity of the TiO2 P25 for phenol degradation by 52% (377% after surface normalization), showing its suitable design for water treatment. These results present a promising approach to boost photocatalyst activity as the combined result of the exposed crystal facet and dopant-optimized density of ground-state charge carriers.

Performance optimization study of lead-free CsSnGeI3 based perovskite solar cell heterostructure with different inorganic electron transport layers: A numerical simulation approach

Perovskite solar cells (PSCs) are considered to be one of the most prominent candidates for its commercialization. The meteoric properties of the PSC have always astounded the researchers. Thus, in this perspective, the germanium-based PSCs are able to increase a sense of curiosity among photovoltaic (PV) researchers due to its superior stability and efficiency. In the present work, different combinations of the lead-free and non-toxic inorganic caesium tin-germanium (CsSnGeI3) based PSC structures have been studied using various electron transport layers (ETLs) (SnS2, TiO2, WS2, MoTe2 and ZnSe) and Mg–CuCrO2 as a hole transport layer due to its meteoric properties. For each ETL, the impact of material parameters including the thickness of the various layers, absorber acceptor density, donor density, absorber defect density, absorber radiative recombination and interfacial defect density are examined to study the cell performance (such as Voc, Jsc, FF, and PCE). Moreover, the role of operating temperature, shunt resistance and series resistance in analysing the cell performance has also been checked towards its practical applicability. The results show ZnSe as the best ETL in comparison to other inorganic ETLs for CsSnGeI3 based absorber with Mg–CuCrO2 as an HTL, used in this work resulting in a good cell performance with a power conversion efficiency (PCE) of 33.24%, Voc ∼ 1.36 V, Jsc ∼ 28.02 mA/cm2 and fill factor (FF) ∼ 86.79%. The proposed simulation work may pave the way for further design and optimization of Sn-based PSCs towards practical applications.

In-situ electron capture by surface Co-Ci to facilitate the solar water splitting of Fe2O3

Surface co-catalyst has been widely used to improve the performance of hematite for solar water splitting. However, the specific working mechanism for co-catalyst has not yet been extensively studied, especially lacking for in-situ information. Here we report a Co-Ci/Zr-Fe2O3 (LV) photoanode for efficient water splitting and probe the working mechanism of surface Co-Ci by in-situ X-ray absorption spectroscopy (XAS) under illumination. The low vacuum treatment and the Zr-doping in Co-Ci/Zr-Fe2O3 (LV) can significantly increase the donor density and then facilitate the bulk charge transfer, while the surface Co-Ci co-catalyst can greatly reduce the electron-hole recombination and then lower the onset potential. In-situ XAS reveals that under illumination, the photon-excited electrons will be quickly transferred to the Co sites in Co-Ci, while the excited holes will be left on Fe to form the high-valence Fe4+ to enhance the oxidation capability. As a result, the combined Co-Ci/Zr-Fe2O3 (LV) photoanode shows a quick bulk charge transfer and a low surface charge recombination, leading to a high photocurrent density of 4.10 mA/cm2 (1.23 VRHE) and a low onset potential of 0.85 VRHE with good stability.