Photoconversion Efficiency Research Articles

Increased oxygen vacancies and Sc doping in ZnO promote bacterial disinfection and methyl orange degradation

Semiconductor materials exhibit poor absorption of visible light as well as high charge recombination rates, which considerably limit their photoconversion efficiency. In this study, a higher photoconversion versatile photocatalyst, namely ZnO@SiO2 was doped with Sc and was synthesized to degrade methyl orange and inactivate bacteria efficiently. Although the undoped materials were oxygen vacant, they failed to efficiently degrade organic pollutants. What our research demonstrates is the effectiveness of Sc addition to making such ZnO material for the degradation of methyl orange and inactivation of bacteria. In addition, we have studied in detail the process of superoxide anions damage to methyl orange and Escherichia coli during degradation, and this study will guide the expansion of applications in photocatalysis by doping with rare earth elements. Meanwhile, this material with no color has potentially valuable applications in water purification.

Dual-Functional Z-Scheme TiO2 @MoS2 @NC Multi-Heterostructures for Photo-Driving Ultrafast Sodium Ion Storage.

Exploiting dual-functional photoelectrodes to harvest and store solar energy is a challenging but efficient way for achieving renewable energy utilization. Herein, multi-heterostructures consisting of N-doped carbon coated MoS2 nanosheets supported by tubular TiO2 with photoelectric conversion and electronic transfer interfaces are designed. When a photo sodium ion battery (photo-SIB) is assembled based on the heterostructures, its capacity increases to 399.3 mAh g-1 with a high photo-conversion efficiency of 0.71 % switching from dark to visible light at 2.0 A g-1 . Remarkably, the photo-SIB can be recharged by light only, with a striking capacity of 231.4 mAh g-1 . Experimental and theoretical results suggest that the proposed multi-heterostructures can enhance charge transfer kinetics, maintain structural stability, and facilitate the separation of photo-excited carriers. This work presents a new strategy to design dual-functional photoelectrodes for efficient use of solar energy.

Effect of polystyrene microplastics on tetracycline photoconversion under simulated sunlight: Vital role of aged polystyrene

Photoconversion of tetracycline (TC) has been widely reported. However, the effect of microplastics (MPs) on TC conversion kinetics and mechanism has rarely been discussed. In this study, we investigated the effect of (aged) MPs on TC degradation under simulated sunlight and elucidated the underlying mechanism. Our findings demonstrated that the physical and chemical properties of polystyrene (PS), such as particle size, surface groups, and morphology, were significantly altered after aging. Moreover, photoconversion efficiency of TC was suppressed with the spiking of aged PS, while virgin PS showed an opposite tendency. The photodegradation reaction for photosensitization of PS involved 1O2 and HO·. The light-screening effect of aged PS occupied predominance, weakening the direct UV-light absorption of TC and resulting in lower TC degradation efficiency. Additionally, triplet-excited state PS was generated after photon acceptance by aged PS, which could transfer energy to O2, leading to the production of 1O2. The toxicity test manifested that the direct impact of TC products on fathead minnow was ignorable, but long-term negative effects on growth deserved observation. This study enhances our understanding of the environmental fate of PS and TC under sunlight, and provides crucial reference information for better evaluating the potential risk of MPs and chemicals.

Impact of tin-based perovskite as a hole transport layer on the device performance of stable and 27.10% efficient CdTe-based solar cell by numerical simulation

In this work, a numerical simulation study on cadmium telluride (CdTe)-based thin film solar cell structure utilizing CdTe as absorber layer, Cadmium sulphide (CdS) as window layer, and lead-free perovskite (CH3NH3SnBr3) as a hole transport layer (HTL) is presented for the first time. The effect of different material parameters such as shallow uniform acceptor density (NA) of absorber and HTL, thicknesses of absorber and HTL, Electron affinity of HTL, defect density of absorber layer, series and shunt resistance, back contact metal work function, and operating temperature on photovoltaic (PV) parameters such as open-circuit voltage (Voc), short circuit current (Jsc), fill factor (FF), and photo conversion efficiency (PCE) has been studied. With the introduction of perovskite as HTL, it is observed that Voc increased from 0.66 V to 1.17 V by creating a suitable band alignment with the CdTe absorber layer, causing an improvement in efficiency by preventing carrier recombination at the back contact surface. The designed solar cell has shown an enhanced PCE of 27.10% with Voc ∼1.17 V, Jsc ∼27.76 mA/cm2, and FF ∼83.40%. Thus, from the study, it is possible to achieve high-performance CdTe-based solar cells using perovskite as HTL for photovoltaic applications.

Revealing the photophysics of N719 dye based dye-sensitized solar cell

Dye-sensitized solar cell (DSSC) has demonstrated promising photovoltaic performance with several photo-sensitizers. N719 dye, is a popular sensitizer used in DSSC due to its ability to absorb light in the visible region and its unique characteristics such as ultrafast electron injection and stable anchoring to the TiO2 surface. However, many of its intriguing optoelectronic properties and charge carrier relaxation at low frequency are contested. Here impedance and modulus spectroscopy were employed to extensively explore the charge carrier dynamics under both light-off and illumination conditions, and it was found that there is a significant change observed in the low-frequency regime in both cases. The fabricated N719 dye based DSSC exhibit the highest JSC of 10.89 mA/cm2, a highest VOC of 0.672 V, a fill-factor of 0.65 and photoconversion efficiency of 4.81%. The Nyquist plot of N719 DSSC under light-off and illumination conditions demonstrates that at higher frequency, a small arc is observed, and at a lower value, a large arc is observed. Moreover, the Nyquist plots exhibit depressed semicircles due to deviation from ideal Debye relaxation nature. The dielectric relaxation is found to follow the interfacial polarization of Maxwell-Wagner type probably attributed to the grain boundary effects. Furthermore, the comparative analysis of modulus and impedance spectra at low frequency reveals the localized carrier relaxation in this N719 DSSC which has been correlated with conductivity hopping process.

Modeling and Simulation of Efficiency of Five Junction Solar Cell Using MSCS-1D Simulator

The third-generation multijunction solar cell (MJSC) is the most promising solar cell in terms of champion photoconversion efficiency. This advanced photovoltaic solar cell is considered as the future green electricity source to meet the gradually increasing terrestrial energy demand. Usually, MJSC consists of 2 to 6 semiconducting materials. These materials work as the sub-cells or sublayers in a multijunction solar cell. This sub-cell is selected in a fashion so that it can absorb the entire solar spectrum. In this project, the efficiency of a novel solar cell has been investigated. A detailed analysis of each sub-cell has been done using the state-of-the-art MSCS-1D simulation software. The materials of each sub-cell of the solar cell have been selected so that they can efficiently utilize the entire ultraviolet to infrared spectrum. The optoelectronic parameters used in the simulation were collected from the standard references. The photoconversion efficiency of this model is simulated to be 48.29% and 59% for AM1.5G solar radiation under one sun and 500 sun conditions, respectively. These simulation results will assist in realizing the performance of the 5-junction solar cell in practical fabrication.
 J. of Sci. and Tech. Res. 4(1): 37-48, 2022

A Synergic Effect of Bi-metallic Layered Hydro-Oxide Cocatalyst on 1-D TiO2 Driven Photoelectrochemical Water Splitting

ABSTRACT Photoelectrochemical (PEC) water splitting is one of the most sustainable approaches for converting solar energy into hydrogen fuel. Affordable and robust photoelectrodes are crucial for the commercialization of PEC technologies. Recently, transition metal-based co-catalysts, especially Ni- and Fe-based catalysts, have attracted much interest owing to their exceptional OER characteristics. Given this, we here proposed the decoration of a Fe-Ni-based cocatalyst on the surface of the TiO2 photoanode for PEC water splitting. The TiO2 photoanode was hydrothermally synthesized and then decorated by Fe-Ni hydroxide catalyst using photo-assisted electrodeposition. The optimized TiO2/FeNiOOH photoanode exhibited the maximum photocurrent density value of 1.36 mA cm−2, which is almost twice the value obtained for bare TiO2, at 1.23 V vs RHE under the AM 1.5 G illumination. Due to the enhanced light absorption in the UV region, the optimized photoanode exhibited remarkable IPCE and photoconversion efficiency of 87.8% and 0.93%, respectively. Furthermore, excellent faradaic efficiencies of ∼90% for H2 and ∼70% for O2 generations were obtained. Predominantly, the enhancement in the photocurrent potentials was explained in detail. Our study shows the roles and benefits of using bimetallic catalysts with TiO2 photoanodes for sustainable water-splitting applications.

Printable Organic Photodetectors With Gain Toward High-Performance Vertically Stacked Color Sensors

Vertically stacked photodetectors based on printable organic semiconductors have considerable potential to deliver high-performance, low-cost, filterless color sensors, which are highly sought after for a host of emerging applications. To realize the full potential of this technology, however, it is critical to minimize the impact of the optical losses occurring at the electrodes, which reduce the photon flux reaching deep into the device stack. To this end, here we propose the use of organic photodiodes with photoconductive gain within a vertically stacked device architecture. We first realize polymer-based green- and red-sensitive photodiodes with external quantum efficiencies (EQEs) greater than 100 % and optimize their processing and spectral properties for color sensing. We then analyze their integration in a vertical device stack atop a blue-selective photodetector to achieve red-green-blue (RGB) color sensing. Finally, we examine the ultimate limit of this approach for multispectral/hyperspectral light sensing. The resulting large and balanced photoconversion efficiencies for all RGB color bands and beyond demonstrate the potential of vertically stacked organic photodetectors with gain for high-performance, low-cost color/multispectral/hyperspectral sensors and imagers.

Deciphering the role of (Er3+/Nd3+) co-doping effect on TiO2 as an improved electron transport layer in perovskite solar cells

Charge injection and transport at the interface of the electron transport layer (ETL) and perovskite interface are crucial for the perovskite solar cell (PSC) device performance. Titanium dioxide (TiO2) is well established as a photoanode in numerous solar energy conversion and storage. The bandgap engineering of TiO2 by Rare-Earth (RE)-doping has become a significant way to improve the optoelectronic device performance. This study demonstrates the improved performance of Rare-Earth doped TiO2 (RETO) photoanode based solar cells under the doping of Er3+, Nd3+ and following codoping of the (Er3+/Nd3+) effect. It is note that the Er, and Nd dopants are responsible for producing Ti3+ states and the oxygen vacancies near the surface, which drives the charge transportation much more effectively. With the (Er/Nd) codoping into TiO2, the band structure of TiO2 is modified better to make a quasi-Ohmic contact with the perovskites, by fermi level shifting as well changes in the conduction band minima (ECBM) energy states. This results evidence the preliminary conformation for the improvement of Jsc and Voc. Furthermore, the photoluminescence (PL) emission quenching effects of perovskite-deposited RETO attributes the suppression in the charge recombination. By insight into all these favourable results in the(Er3+/Nd3+) codoped TiO2, the RETO photoanode-based perovskite solar cell (PSC) devices were constructed and exhibited improved photovoltaic properties. The composition of (Er0.002Nd0.002Ti0.996O2) ETL employed PSC reported with a better photoconversion efficiency (PCE %) among all the compositions.

Engineering interfacial band hole extraction on chemical-vapor-deposited MoS2/CdS core-shell heterojunction photoanode: The junction thickness effects on photoelectrochemical performance

Heterojunction fabrication is a promising strategy that can greatly boost the charge carrier separation and improve the solar-to-hydrogen conversion efficiency of photoelectrochemical (PEC) cells. However, such technology still suffers from limited contact interfaces. In this study, the chemical vapor deposition (CVD) technique was for the first time used to construct the CdS/MoS2 heterojunction photoanode with a unique core-shell nanoarchitecture, in which a continuous crystalline MoS2 nanosheet layer was grown directly on one-dimensional (1D) oriented CdS nanorods (NRs) in a plane-to-plane stacking fashion. The optimization of junction thickness with adjustable MoS2 loading from mono to a few layers was achieved by experimental parameters variation. Systematic characterizations show that the MoS2 shell plays a dual role as an optical absorption booster for more photo-exciton generation and a surface passivator of trap states. Meanwhile, the formed heterojunction helps regulate the unidirectional charge migration for a significantly suppressed electron-hole recombination process, which synergistically contributes to higher quantum yield and efficiency. As a result, the optimized CdS/MoS2 heterojunction photoanode with 3-layered MoS2 wrapping exhibits the highest photocurrent density and photoconversion efficiency, over a two-fold increase, compared to those of pristine CdS and the previously reported CdS/MoS2 heterojunctions. Moreover, due to the rapid hole extraction from CdS and transferred surface oxidation sites, the present CdS/MoS2 heterostructure demonstrates better corrosion resistance and higher photostability. The present work is expected to provide a versatile platform for exploiting the CVD technique to develop other MoS2-based heterojunction photoelectrodes with extensive PEC applications.

Improving the efficiency of a FTO/PCBM/Cs2AgBiBr6/NiOx/Au lead-free double perovskite solar cell using numerical simulation through optimizing the absorption layer thickness and work function of electrodes

Lead-free perovskite solar cells are proposed to reduce environmental toxicity. However, the efficiency of these solar cells is significantly lower than that of those based on lead. The maximum Photo Conversion Efficiency(PCE) reported experimentally for lead free solar cells is 6.37%, which is significantly lower than that of lead-based solar cells. Attempts have been made to improve the PCE of lead-free solar cells using numerical simulations in order to build a lead-free solar cell with the highest efficiency attainable. Recently, a lead-free solar cell with the configuration ITO/SnO2/Cs2AgBiBr6/P3HT/Au and a maximum PCE of 11.69% was numerically investigated. In this study, we suggested a lead-free solar cell structure using FTO/PCBM/Cs2AgBiBr6/NiOx/Au configuration and showed that,when operated in the wavelength range 400–700 nm, a PCE of 15.49% with Jsc = 8.17 mA/cm2, Voc = 2.49 V and FF = 76.16% can be attained by optimizing the thickness of the absorption layer and the work function of the electrode. While in the same configuration the PCE can be increased to 21.92% when operated in the wavelength range of 350–750 nm.This investigation's findings can be used to manufacture more efficient and stable lead-free solar cells forfuturenon-hazardous environmental applications.

Enhancing the performance of the perovskite solar cells by modifying the SnO2 electron transport layer

The tin oxide (SnO2) electron transport layer (ETL) plays a vital role in the photo-conversion efficiency (PCE) and stability of organic-inorganic perovskite solar cells (PSCs). However, SnO2 ETL-induced defects such as hydroxyl groups, oxygen vacancies, exposed Sn atoms, and dangling bonds hinder device performance. In this study, rubidium chloride (RbCl) has been used to modify the SnO2 ETL. Perovskite film formed on the RbCl-modified SnO2 ETL exhibits improved crystallinity with enlarged grain size and reduced grain boundaries and enhanced optical absorption. The Hall-effect measurements indicate the improved carrier mobility, and the dark J-V curve shows the increment of electrical conductivity for the RbCl-modified SnO2 ETL. X-ray photoelectron spectroscopy (XPS) results demonstrate the surface defects passivation of the perovskite layer by modifying the SnO2 ETL. A champion PCE of 19.35% has been achieved for the RbCl-modified SnO2 ETL-based devices with improved stability, while the control devices with unmodified SnO2ETL show a PCE of 17.18%.

Mn-doped ZnS nanoparticle photoanodes: Synthesis, structural, optical, and photoelectrochemical characteristics

In this work, Mn-doped zinc sulfide (Mn:ZnS) nanoparticles (NPs) have been synthesized as a promising material for photoelectrochemical water splitting (PEC), using the co-precipitation method. PEC properties of Mn-doped zinc sulfide NPs were considered under the correlation between Mn-doping level and their particle size. The highest photocurrent density (8.03 mA cm−2) and largest photoconversion efficiency (0.63%) (at 0.4 V vs. RHE) were reached at 6 mol% Mn. Based on the results of used various materials characterization techniques, including transmission electron microscopy (TEM), X-ray diffraction, photoluminescence spectrum, and absorbance spectrum, it can be assessed that the outstanding PEC characteristics of Mn:ZnS photoanode are attributed to the narrow bandgap of Mn:ZnS nanoparticles and their notably small particle size, which is originated from the Mn-doping. For application, the stability and the effect of various electrolytes were also investigated.

Aluminum-doped zinc oxide (AZO) ultra-thin films deposited by radio frequency sputtering for flexible Cu(In,Ga)Se2 solar cells

Zinc oxide ultra-thin films doping with aluminum (AZO) were produced through radio frequency (rf) sputtering at a fixed pressure of 10 mTorr while varying the rf power between 80 and 140 W. The crystal structure of hexagonal Wurtzite was consistent throughout, with improved crystallinity observed at higher rf powers due to optimal diffusivity of the sputtered particles during nucleation and growth. The size of the crystallite was increased from 10.37 to 16.58 nm with increasing the rf power from 80 to 140 W. The Raman spectra provided evidence of the formation of ultra-thin AZO films, with discernable changes in morphology due to the influence of rf power. The value of optical band gap fluctuated between 3.49 and 3.58 eV as a function of rf power, a basis of the Burstein–Moss effect. The resistivity of the ultra-thin AZO films declined while augmenting rf power. A bilayer structure of intrinsic ZnO (i-ZnO) and AZO was fabricated and exhibited good transmittance, well-crystalline morphology, and excellent electrical conductivity. The optimized window layer (i-ZnO and AZO) was used to produce flexible Cu(In,Ga)Se2(CIGSe) solar cells with a photo conversion efficiency of 9.53%. Therefore, ultra-thin ZnO films exhibit potential as a favorable option for a window layer in the production of high-efficient flexible solar cells in cost effective way.

Deep Insights into the Coupled Optoelectronic and Photovoltaic Analysis of Lead-Free CsSnI3 Perovskite-Based Solar Cell Using DFT Calculations and SCAPS-1D Simulations.

CsSnI3 is considered to be a viable alternative to lead (Pb)-based perovskite solar cells (PSCs) due to its suitable optoelectronic properties. The photovoltaic (PV) potential of CsSnI3 has not yet been fully explored due to its inherent difficulties in realizing defect-free device construction owing to the nonoptimized alignment of the electron transport layer (ETL), hole transport layer (HTL), efficient device architecture, and stability issues. In this work, initially, the structural, optical, and electronic properties of the CsSnI3 perovskite absorber layer were evaluated using the CASTEP program within the framework of the density functional theory (DFT) approach. The band structure analysis revealed that CsSnI3 is a direct band gap semiconductor with a band gap of 0.95 eV, whose band edges are dominated by Sn 5s/5p electrons After performing the DFT analysis, we investigated the PV performance of a variety of CsSnI3-based solar cell configurations utilizing a one-dimensional solar cell capacitance simulator (SCAPS-1D) with different competent ETLs such as IGZO, WS2, CeO2, TiO2, ZnO, PCBM, and C60. Simulation results revealed that the device architecture comprising ITO/ETL/CsSnI3/CuI/Au exhibited better photoconversion efficiency among more than 70 different configurations. The effect of the variation in the absorber, ETL, and HTL thickness on PV performance was analyzed for the above-mentioned configuration thoroughly. Additionally, the impact of series and shunt resistance, operating temperature, capacitance, Mott-Schottky, generation, and recombination rate on the six superior configurations were evaluated. The J-V characteristics and the quantum efficiency plots for these devices are systematically investigated for in-depth analysis. Consequently, this extensive simulation with validation results established the true potential of CsSnI3 absorber with suitable ETLs including ZnO, IGZO, WS2, PCBM, CeO2, and C60 ETLs and CuI as HTL, paving a constructive research path for the photovoltaic industry to fabricate cost-effective, high-efficiency, and nontoxic CsSnI3 PSCs.

The effect of foamed cement nanocomposite as counter electrode on the performance of dye‐sensitized solar cell

AbstractImproper interparticle connection between carbon‐based materials, poor interface bonding between the carbon counter electrodes (CEs) and substrate, and low surface area are the main limitations of carbon‐based CEs in dye‐sensitized solar cells. In this study, we utilized foamed cement and binder for adherence and surface area improvement in carbon‐based CEs, such as graphite, multi‐walled carbon nanotubes, and carbon black (CB). The results revealed that incorporating foamed cement into carbon materials improved the resistance, short‐circuit current density, fill factor, and power conversion efficiency of the device. The porous cement/CB nanocomposite CE with a photoconversion efficiency of 5.51% exhibited the best photovoltaic performance. Moreover, this nanocomposite electrode showed an enhancement catalytic activity by high current density in cyclic voltammogram, low charge transfer resistance ) in electrochemical impedance spectroscopy, and high exchange current density in Tafel measurements compared to other electrodes. The porosity of foamed cement has been found to be the main cause of its superior photovoltaic performance, which expands the contact area with the electrode and enables rich ion transport. Additionally, the enhanced performance was due to strong bonding, crack‐free deposited films, superior conductivity, and high catalytic activity.

GPP-TSAIII nanocomposite hydrogel-based photothermal ablation facilitates melanoma therapy

ABSTRACT Background Photothermal therapy (PTT) is a promising cancer treatment, but its application is limited by low photoconversion efficiency. In this study, we aimed to develop a novel graphene oxide (GO)-based nanocomposite hydrogel to improve the bioavailability of timosaponin AIII (TSAIII) while maximizing PTT efficacy and enhancing the antitumor effect. Methods GO was modified via physical cross-linking with polyvinyl alcohol. The pore structure of the gel was adjusted by repeated freeze-thawing and the addition of polyethylene glycol 2000 to obtain a nanocomposite hydrogel (GPP). The GPP loaded with TSAIII constituted a GPP-TSAIII drug delivery system, and its efficacy was evaluated by in vitro cytotoxicity, apoptosis, migration, and uptake analyses, and in vivo antitumor studies. Results The encapsulation rate of GPP-TSAIII was 66.36 ± 3.97%, with slower in vitro release and higher tumor cell uptake (6.4-fold) compared to TSAIII. GPP-TSAIII in combination with PTT showed better bioavailability and antitumor effects in vivo than did TSAIII, with a 1.9-fold higher tumor suppression rate than the TSAIII group. Conclusions GPP is a potential vehicle for delivery of TSAIII-like poor water-soluble anticancer drugs. The innovative PTT co-delivery system may serve as a safe and effective melanoma treatment platform for further anticancer translational purposes.

Two-photon lifetime-based photoconversion of EGFP for 3D-photostimulation in FLIM

Enhanced green fluorescence protein (EGFP) is a fluorescent tag commonly used in cellular and biomedical applications. Surprisingly, some interesting photochemical properties of EGFP have remained unexplored. Here we report on two-photon-induced photoconversion of EGFP, which can be permanently converted by intense IR irradiation to a form with a short fluorescence lifetime and spectrally conserved emission. Photoconverted EGFP thus can be distinguished from the unconverted tag by the time-resolved detection. Nonlinear dependence of the two-photon photoconversion efficiency on the light intensity allows for an accurate 3D localization of the photoconverted volume within cellular structures, which is especially useful for kinetic FLIM applications. For illustration, we used the two photon photoconversion of EGFP for measurements of redistribution kinetics of nucleophosmin and histone H2B in nuclei of live cells. Measurements revealed high mobility of fluorescently tagged histone H2B in the nucleoplasm and their redistribution between spatially separated nucleoli.

Vertically Aligned Nanowires and Quantum Dots: Promises and Results in Light Energy Harvesting.

The synthesis of crystals with a high surface-to-volume ratio is essential for innovative, high-performance electronic devices and sensors. The easiest way to achieve this in integrated devices with electronic circuits is through the synthesis of high-aspect-ratio nanowires aligned vertically to the substrate surface. Such surface structuring is widely employed for the fabrication of photoanodes for solar cells, either combined with semiconducting quantum dots or metal halide perovskites. In this review, we focus on wet chemistry recipes for the growth of vertically aligned nanowires and technologies for their surface functionalization with quantum dots, highlighting the procedures that yield the best results in photoconversion efficiencies on rigid and flexible substrates. We also discuss the effectiveness of their implementation. Among the three main materials used for the fabrication of nanowire-quantum dot solar cells, ZnO is the most promising, particularly due to its piezo-phototronic effects. Techniques for functionalizing the surfaces of nanowires with quantum dots still need to be refined to be effective in covering the surface and practical to implement. The best results have been obtained from slow multi-step local drop casting. It is promising that good efficiencies have been achieved with both environmentally toxic lead-containing quantum dots and environmentally friendly zinc selenide.

WO3 layer sensitized with BiVO4 and MIL-101(Fe) as photoanode for photoelectrochemical water oxidation

Thick tungsten oxide layers were prepared electrophoretically in order to be used as photoanodes in photoelectrochemical water oxidation applications. The highest photocurrent density was obtained for a WO3 layer with thickness of ∼900 nm. Additionally, WO3/BiVO4 and WO3/BiVO4/MIL-101(Fe) heterojunctions have been fabricated using WO3 layer as substrate. WO3/BiVO4 shows an increased value of the electrochemical active surface area indicating that more sites of this photoanode are activated through the formation of the heterojunction. The small V5+ signals observed in the V 2p XPS spectra of these heterojunctions were attributed to the substitution of V5+ atoms with W6+ atoms on the surface of BiVO4. Excessive W doping of the BiVO4 film determined the decrease of the photoelectrochemical performance of WO3/BiVO4 photoanode. The significant improvement of the photoconversion efficiency of the sample decorated with MIL-101(Fe) indicated that this co-catalyst provides sites more efficiently in the photoelectrochemical process. This performance was correlated with the reduced value of the charge transfer resistance at electrode/electrolyte interface obtained from electrochemical impedance spectroscopy investigation.