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CsPbBr3 perovskite exhibits potential application in photocatalytic CO2 reduction into valuable chemical fuels; however, enhancing carrier separation capability of the CsPbBr3 and fully understanding the CO2 reduction reaction process are still imperative. Herein, a new series of xSnS2/CsPbBr3 nanocrystals (NCs)‐y heterostructures are developed, which exhibit better catalytic activity in comparison with pure CsPbBr3 NCs. Interface and surface carrier dynamic investigation reveals that this heterojunction structure can effectively improve carrier separation efficiency. Based on the interfacial electric field direction of CsPbBr3 to SnS2, it is suggested that SnS2/CsPbBr3 NC heterostructure satisfies Z‐scheme transfer dynamics. Meanwhile, by the aid of in situ surface photovoltage, it is experimentally confirmed there is dynamic carrier interaction between CO2 molecules and the SnS2/CsPbBr3 NCs photocatalyst under irradiation, and a photocatalytic CO2 reduction mechanism is thus proposed. This work expands the awareness of the interaction between CO2 and the photocatalyst, which can be strongly influenced by carrier separation efficiency at the photocatalyst heterojunction. [ABSTRACT FROM AUTHOR]

Decorating a high-efficiency oxygen evolution reaction (OER) electrocatalyst as a cocatalyst on an α-Fe2O3 photoanode is known to be one of the most efficient methods to improve the photoelectrochemical (PEC) water oxidation activity. In our work, different from traditional methods of transition metal sulfide cocatalyst synthesis, an NiFeSx–decorated Ti-Fe2O3 photoanode is synthesized through a simple one-step electrodeposition method, which benefits the interface between Ti-Fe2O3 and NiFeSx. With the help of this excellent OER electrocatalyst, the photocurrent density of the NiFeSx–Ti-Fe2O3 photoanode rises to 3 mA cm−2 at 1.23 V vs. RHE, which is 2.5 times greater than the photocurrent of Ti-Fe2O3. Moreover, the onset potential of NiFeSx–Ti-Fe2O3 shifts negatively by 170 mV compared with that of pure Ti-Fe2O3. Furthermore, surface photovoltage spectroscopy (SPV) and transient photovoltage (TPV) techniques and photoelectrochemical impedance spectroscopy (PEIS) were used to analyze the true effects of NiFeSx as an efficient cocatalyst for enhancing the PEC performance of the NiFeSx–Ti-Fe2O3 photoanode. This work provides a simple method for loading a low-cost and efficient cocatalyst to modify a Ti-Fe2O3 photoanode for the PEC water oxidation reaction. [ABSTRACT FROM AUTHOR]

Abstract: Although NiCoP has attracted much attention in the field of electrocatalysis, the study of its photocatalytic activity and mechanism have been somewhat limited. NiCoP/g‐C3N4, synthesized by simple one‐pot method, is a highly efficient photocatalyst for hydrogen production from water. NiCoP/g‐C3N4 exhibits a hydrogen evolution rate of 1643 μmol h−1 g−1, which is 21 times higher than that of bare g‐C3N4. The excellent performance is due to a combination of improved separation efficiency and effective charge transfer efficiency. The photogenerated charge behavior is characterized by the surface photovoltage (SPV), transient photovoltage (TPV), and photoluminescence spectroscopy. The photogenerated charge transport is investigated by electrochemical impedance spectroscopy and polarization curve. Moreover, the effective charge transfer efficiency was measured according to the mimetic apparent quantum yield. SPV and TPV measurements, whereby 10 vol % of a triethanolamine–water mixture was added into the testing system, were taken to simulate the real atmosphere for photocatalytic reaction, which can give rise to the photogenerated charge transfer process. A possible photocatalytic mechanism was also proposed. This study may provide an efficient theoretical basis to design transition metal phosphide cocatalyst‐modified photocatalysts. [ABSTRACT FROM AUTHOR]

Bimetallic materials hold promise for improving catalyst activity, yet little is known about the photocatalytic mechanism that these systems undergo during photocatalytic reaction that lead to efficient catalyst. Herein, we synthesized g-C3N4 combined with PtNi x, which shows much higher photocatalytic activity than that of pure g-C3N4 and achieves the highest H2 evolution rate of 8456 μmol h−1 g−1 for 2.5 % PtNi x/g-C3N4. The excellent photocatalytic activity resulted from the enhanced charge-separation efficiency compared to the pristine g-C3N4, which was proved by surface photovoltage, photoluminescence, and transient photovoltage spectra. Electrochemical impedance spectroscopy in the dark further confirms the ability of charge transfer of 2.5 % PtNi x/g-C3N4 is superior to that of pure g-C3N4. This effective separation efficiency gives rise to the observed excellent photocatalytic activity. This study not only provides us with an efficient catalyst for water splitting, but opens new avenues for designing and developing platinum-based photocatalysts. [ABSTRACT FROM AUTHOR]

A series of nano-spindly BiVO 4 and Ag-BiVO 4 were synthesized by a simple solvothermal method. X-ray photoelectron spectroscopy (XPS) and high resolution electron microscopy (HRTEM) analysis indicated that the chemical state of the Ag particles was metallic Ag. Their photocatalytic activities were evaluated by the decolorization of rhodamine B (RhB) under visible light irradiation ( λ > 420 nm). The research of photoinduced charge properties of samples studied by surface photovoltage spectroscopy (SPS) and electric field-induced surface photovoltage spectroscopy (FISPS) measurement system and the results indicated that the existence of Ag attained the enhancement of photoinduced charge carriers’ separation. This was thought to be responsible for the higher efficient photocatalytic activity of Ag-BiVO 4 in the degradation of RhB. [ABSTRACT FROM AUTHOR]

Abstract: Ag–ZnO nanorods with enhancement in UV light photoelectric gas-sensing response properties were synthesized by a facile two-step process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution electron microscope (HRTEM) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The results revealed that Ag nanoparticles have decorated the surface of ZnO nanorods successfully. Formaldehyde (HCHO) sensing properties of sensors based on the Ag–ZnO nanorods were also investigated under 370nm light irradiation at room temperature with the assistance of surface photocurrent technique. It was found that the as-prepared Ag–ZnO nanorods showed excellent gas-sensing property that the gas response to 5 and 40ppm formaldehyde can reach to 9.4% and 119.8% under 370nm light irradiation at room temperature, respectively. To better understand the reason for the enhanced gas-sensing properties of Ag–ZnO, the separation and transfer behavior of the photogenerated charges were characterized by means of surface photovoltage and phase spectra. The results indicated that an electronic interaction between Ag and ZnO formed. Ag, as electron acceptor, effectively promoted the charge separation and transfer ability and, at the same time, inhibited the recombination of photogenerated charge carriers in ZnO, thus the Ag–ZnO nanorods had a high gas-sensing response to HCHO at room temperature. [Copyright &y& Elsevier]

Abstract: In this study TiO2 nanotube arrays were fabricated by potentiostatic anodization of titanium sheet. The X-ray diffraction (XRD) pattern and field emission scanning electron microscopy (FE-SEM) image indicated the TiO2 nanotube arrays were of pure anatase form and highly ordered. The properties of the photo-generated charges in the nanotube arrays were investigated by transient photovoltage (TPV) technique and surface photovoltage (SPV) technique based on lock-in amplifier with dc bias, in comparison with the commercial powder derived film. The separation processes of the photo-induced charges in the system of TiO2 nanotubes on Ti have been demonstrated to be correlated with the incident light intensity, surface trapping states, and the interfacial electric field between Ti and TiO2. The results also show that the highly ordered nanotube film could generate much stronger SPV responses under external electric field than the commercial powder derived film. [Copyright &y& Elsevier]

By the aid of transient photovoltage, photo-generated carrier transfer mechanism of SnS 2 /g-C 3 N 4 composite has been suggested by interfacial electric field direction. Constructing heterojunction is an effective way to improve the photo-generated carrier separation efficiency and photocatalytic activity. Here, we construct SnS 2 /g-C 3 N 4 heterojunctions by in-situ growth of SnS 2 on the g-C 3 N 4. By adjusting annealing temperatures, the SnS 2 /g-C 3 N 4 -180 and SnS 2 /g-C 3 N 4 -120 samples could meet Z-scheme carrier transfer mechanism and conventional type-II charge transfer mechanism, respectively. By the aid of surface photovoltage spectra, the photo-generated carrier transfer direction and the driving force of the charge transfer are suggested. This difference in these two charge transfer mechanisms is supposed to be mainly related to the discrepancy in work functions of the SnS 2 treated at different temperatures. This work provides an effective method to understand the Z-scheme carrier transfer mechanism, which could help us to design Z-scheme photocatalysts for higher hydrogen evolution activity. [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]

Improving the water-splitting performance of hematite (α-Fe 2 O 3) is still hindered due to its severe charge recombination and poor water oxidation kinetics. Herein, borate-treated Ti–Fe 2 O 3 combined with a Fe x Ni 1-x OOH cocatalyst (Fe x Ni 1-x OOH/B/Ti–Fe 2 O 3) greatly improved the performance of Ti–Fe 2 O 3 , and reached a notable photocurrent density of 3.39 mA/cm2 at 1.23 V vs. RHE. Transient surface photovoltage spectroscopy (TPV) directly reveals that [B(OH) 4 ]− as a Lewis base can selectively passivate acceptor surface states on Ti–Fe 2 O 3 photoanode surface, efficiently enhancing the charge separation efficiency. Moreover, the Fe x Ni 1-x OOH thin layer is devoted to further facilitate holes injection into the electrolyte, accelerating the water oxidation kinetics of Ti–Fe 2 O 3 photoanode. The synergetic integration of acceptor surface states passivation and Fe x Ni 1-x OOH cocatalyst provides a novel strategy for the construction of efficient photoanodes by surface engineering. [Display omitted] • [B(OH) 4 ]− as a Lewis base can selectively passivate acceptor surface states. • The Fe x Ni 1-x OOH thin layer can further improve water oxidation kinetics. • Fe x Ni 1-x OOH/B/Ti–Fe 2 O 3 could achieve 3.39 mA/cm2 at 1.23 V vs. RHE. • Fe x Ni 1-x OOH/B/Ti–Fe 2 O 3 exhibits the outstanding PEC performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Z-scheme NH 2 -MIL-125(Ti)/Ti-Fe 2 O 3 photoanode is designed and constructed. • NH 2 -MIL-125(Ti)/Ti-Fe 2 O 3 shows excellent PEC performance and stability. • The Z-scheme pathway is identified by surface photovoltage, ESR and fs-TAS. • Efficient separation of interface and surface carriers is simultaneously realized. The construction of Z-scheme charge transfer pathways simulating natural photosynthesis is considered a promising method for improving reaction driving forces. Here, we modified the surface of titanium doped Fe 2 O 3 (Ti-Fe 2 O 3) nanorods with NH 2 -MIL-125(Ti) (Ti-MOFs) and a promising organic-inorganic hybrid Z-scheme NH 2 -MIL-125(Ti)/Ti-Fe 2 O 3 was successfully prepared. At 1.23 V vs. RHE, the photocurrent density of the composite photoanode reaches 2.67 mA/cm2, which is 5 times higher than that of Ti-Fe 2 O 3. The results of surface photovoltage, ESR and fs-TAS indicate that this improvement is mainly due to the effective Z-scheme charge transfer mechanism providing a strong driving force for charge separation and transport, greatly suppressing carrier recombination and allowing carriers with strong oxidation ability to participate in water oxidation. Meanwhile, NH 2 -MIL-125(Ti) can enhance light absorption and reduce the surface defect state of Ti-Fe 2 O 3. This study not only provides a feasible approach for the photoanode water splitting of traditional inorganic semiconductor/MOF based heterostructures, but also provides rich and effective means for revealing Z-scheme charge transfer mechanism in depth. [ABSTRACT FROM AUTHOR]

Abstract: ZnO nanostructures materials with two-dimensional (2D) plate-like and three-dimensional (3D) flower-like morphologies have been synthesized via facile hydrothermal process. Scanning electron microscopy (SEM), high resolution transmission electron microscope (HRTEM) and X-ray diffraction (XRD) have been used to characterize the samples. We have compared the surface photoelectric properties of flower-like ZnO with that of plate-like ZnO by means of surface photovoltage (SPV), field-induced surface photovoltage (FISPV), transient photovoltage (TPV) and surface photocurrent (SPC) techniques. Based on the photovoltage responses, the influence of the morphology on transfer characteristics of photogenerated charge carriers was discussed. The synthesized flower-like ZnO exhibited more efficient separation and transfer properties of photogenerated charge carriers than that of plate-like ZnO in the UV region due to the special flower-like hierarchical nanostructures. We have also evaluated the photocatalytic activity of the ZnO samples by photodegradation efficiency of RhB. The experiments demonstrated that RhB in aqueous solution was more efficiently photodegraded using flower-like ZnO than plate-like ZnO. The results also show the consistency between the carrier dynamics of photogenerated electron–hole pairs and photocatalytic activity. [Copyright &y& Elsevier]

In this respect, surface photovoltage spectrum (SPV) has been employed to analyze the carrier transfer mechanism of Ti/α-Fe 2 O 3 /g-C 3 N 4 composite photocatalyst system for the first time. That is, photo-generated carrier interfacial transfer direction is suggested to be the charge driving force between Ti/α-Fe 2 O 3 and g-C 3 N 4 , which could determine the Z -scheme carrier transfer mechanism of Ti/α-Fe 2 O 3 /g-C 3 N 4 photocatalysts. This work provides an effective method to understand the Z -scheme carrier transfer mechanism and could help us to design more effective Z -scheme photocatalysts systems. Unlabelled Image • A new method in understanding the Z -scheme carrier transfer mechanism. • Surface photovoltage spectrum is employed to analyze carrier transfer mechanism. • Ti/α-Fe 2 O 3 /g-C 3 N 4 Z-Scheme photocatalyst system is adopted. • Z-scheme transfer system is analyzed from driving force between the interface. [ABSTRACT FROM AUTHOR]

The polyporous SnO 2 -ZnO composites were synthesized by a water-bath method. The 3D center-hollow architecture and polyporous surface were also confirmed by field-emission scanning electron microscope (FE-SEM) and the Brunauer-Emmett-Teller (BET) specific surface area. Meanwhile, structural properties of SnO 2 -ZnO have been investigated by trans-mission electron microscopy (TEM) in 1 mol% SnO 2 -ZnO. The results of photoelectric gas-sensing demonstrated that the 1 mol% SnO 2 -ZnO gas-sensor exhibits not only an excellent response to formaldehyde (HCHO) but also superior sensitivity to low HCHO concentration. The response of 1 mol% SnO 2 -ZnO for the 1 ppm HCHO has reached 30% at room temperature (25 °C), and a detection limit of 0.1 ppm HCHO was achieved. The behavior of photogenerated charge is discussed in detail by means of the surface photovotage (SPV) and the transient photovoltage (TPV) techniques. It was found that the as-prepared 1 mol% SnO 2 -ZnO composites showed excellent separation and transfer efficiency of photogenerated charges carriers. What's more, the TPV spectrum analysis provides convincing evidence that the addition of excess SnO 2 is unfavorable to the transfer of electrons so as to reduce the sensitivity of SnO 2 -ZnO for target gas. This result offers a new window to explain the effect of SnO 2 concentration on the gas sensing characteristics, and provide more information on the fabricating composite materials for gas sensors. [ABSTRACT FROM AUTHOR]

In this paper, a series of BiOI/ZnO photocatalysts containing various BiOI contents were prepared by a facile two-step synthetic method. The structure and crystal phase, morphology, surface element analysis, optical property of as-prepared samples are measured by X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV–Vis diffuse reflectance spectrometry (DRS). BiOI/ZnO photocatalytic activities of the prepared photocatalysts were evaluated by photocatalytic degradation of phenol under simulated light irradiation. The phenol degradation rate reached 99.9% within 2 h under simulated solar light irradiation. The probable photocatalytic mechanism of composites photocatalysts is discussed by active species trapping experiments, the surface photovoltage (SPV), the transient photovoltage (TPV) and photoluminescence (PL) measurements. The results manifest that the superior photocatalytic activity of BiOI/ZnO composites is derived from the strong internal electric field between BiOI and ZnO, which is beneficial for the effective separation and transfer of photogenerated charges in ZnO. Moreover, the loading of BiOI on the surface of ZnO inhibited the recombination of photogenerated charge carriers in ZnO, resulting in excellent photocatalytic activity. On the contrary, the effect of an extension of the light absorption range induced by the introduction of BiOI on the phenol degradation activity is not significant. [ABSTRACT FROM AUTHOR]

In this study, Ce-doped ZnO photocatalysts are successfully prepared by using a simple and facile one-pot water bath method. The as-prepared samples are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–Vis) diffuse spectroscopy and Brunauer-Emmett-Teller (BET) surface area analysis. It is found that the as-synthesized Ce-doped ZnO possessed hollow porous structure, high surface areas and large pore volumes. The photocatalytic degradation efficiency (99%) of methyl orange (MO) with an optimal molar ratio of 0.3% Ce-doped ZnO is realized. The separation behavior of photogenerated electrons-holes pairs was investigated by surface photovoltage (SPV) and transient photovoltage (TPV) technique. The results illuminate that Ce element in Ce-doped ZnO tremendously promotes the separation of charges and inhibits the recombination of photogenerated charge carriers, corresponding to the excellent photocatalytic performance. [ABSTRACT FROM AUTHOR]

Plasmon-enhanced bulk charge separation and migration at Au-CdS interfaces through CDs as the quicker transfer channel, and it is proved that the regulated charge movement pathway and migration dynamic could efficiently accelerate the photocatalytic hydrogen production rate via morphological and interfacial engineering. [Display omitted] • Core-double shelled Au@CDs@CdS NPs are fabricated for photocatalytic H 2 production. • Plasmon effect enhances interfacial charge separation within the bulk of CdS. • CDs act as faster charge migration channels between Au nucleus and CdS outer shell. • The investigations of charge transport dynamics are supported by SPV/TPV methods. The exploitation of morphological engineering strategies enables the design of semiconductor-based photocatalysts with a precision that significantly enhances their photocatalytic activity. In this study, a paradigm has been provided that embeds plasmonic nanostructures within the bulk of the semiconductor, which demonstrates an improvement in interfacial charge transfer and separation. It involves a distinct core-double shelled Au@carbon dots@CdS hybrid, exhibiting excellent photocatalytic H 2 generation under the visible light radiation. The interfacial engineering between the plasmonic nucleus and the semiconductor shell has been performed by the incorporation of carbon dots as faster charge channels. The effective driving force for plasmon-enhanced bulk charge separation of semiconductors and the unhindered interfacial charge transmission derived from carbon dots have been demonstrated by the use of steady state surface photovoltage (SPV) and transient state surface photovoltage (TPV) methods, as well as some intrinsic kinetics information of interfacial photoexcited charge carriers transfer processes. [ABSTRACT FROM AUTHOR]

Cationic surfactant (CTAB) and anionic surfactant (sodium oleate) were used to modify CdS nanocrystals with different surface states. The surfactant CTAB led to surface states of hole traps, while sodium oleate induced surface states of electron traps on the surface of CdS. The photodegradation of rhodamine B (RhB) over these modified CdS nanocrystals was investigated under visible light irradiation. An efficient cycloreversion degradation of RhB occurred over the E-CdS nanocrystals. However, for H-CdS nanocrystals, an efficient N-deethylation reaction concomitant with a subsequent slow cycloreversion reaction of RhB was observed. The E-CdS sample showed a first-order kinetic rate for the cycloreversion degradation of RhB. By contrast, H-CdS sample shows a zero-order kinetic rate for the N-deethylation reaction of RhB followed by a first-order kinetic rate for the cycloreversion degradation. It is revealed that the different kinds of surface traps could significantly affect the dynamic properties of photogenerated charge carriers, which leads to different degradation mechanism of RhB. These findings demonstrate an alternative solution towards developing efficient photocatalysts with high selectivity by constructing different surface trap states. [ABSTRACT FROM AUTHOR]

To better understand the behavior of photogenerated charges in the composite photocatalyst interface is beneficial to the designing of effective photocatalyst for photocatalytic reaction. In our work, the separation and transfer process of photogenerated charges in NiO/TiO 2 nanotube arrays (NiO/TiO 2 NTAs) has been studied by surface photovoltage (SPV) spectroscopy and transient photovoltage (TPV) measurement. Through the experimental results analysis, we find that an interfacial electric field is formed at NiO/TiO 2 NTAs interface, which is attributed to the work function difference between NiO and TiO 2 NTAs. The photogenerated holes in TiO 2 can transfer to the NiO layer along the interface electric field under the ultraviolet irradiation. A large amount of photogenerated holes can be separated effectively and then prolonged the holes lifetime to participate in the photocatalytic oxidation reaction. The above results show that the favorable hole-collecting process of NiO in the surface of TiO 2 NTAs is the main factor being responsible for the increase the photocatalytic efficiency. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) and iron doped zinc oxide (Fe/ZnO) nanoflowers were successfully synthesized via a simple hydrothermal process. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman scattering, ultraviolet–visible (UV–vis) diffuse spectroscopy and scanning electron microscopy (SEM), and it was found that the dopant ions replaced some of the crystal lattice zinc ions, and furthermore, Fe 3+ and Fe 2+ ions coexist. Photocatalytic activities of the catalysts were assessed based on the degradation of rhodamine B (RhB) in aqueous solution under both UV and visible light irradiation ( λ > 420 nm), respectively. All Fe/ZnO samples showed enhanced photocatalytic activity under the irradiation of visible light. On the contrary, Fe/ZnO products displayed poorer performance than that of pure ZnO in the presence of UV light. This phenomenon can be attributed to the coexistence of Fe 3+ and Fe 2+ in the ZnO host. The photophysical mechanism of the UV and visible photocatalytic activity was investigated with the help of surface photovoltage (SPV) and PL measurements, respectively. The results indicated the influence of coexistence of Fe 3+ and Fe 2+ in ZnO host on the separation and transfer behavior of the photogenerated charges in the UV and visible regions, which are distinctly different: under the irradiation of UV light, the recombination of the photogenerated electrons and holes was promoted, whereas the separation and transfer of photogenerated electrons and holes was facilitated under the visible light irradiation. The detailed photocatalytic mechanism and the role of Fe on the photodegradation process are discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] We report a simple one-step hydrothermal synthesis on Ag2S nanoparticles. [•] The photoelectric properties of the Ag2S nanoparticles were studied. [•] A mechanism for the nucleation and growth of Ag2S NPs was proposed. [•] The concentration of surfactants impacts the grain diameter and the photoelectric properties. [Copyright &y& Elsevier]

Highlights: [•] Ag2S-sensitized TiO2 films show good photoelectric responses in visible-light region. [•] Frequency-modulated SPV give dynamic information and evidence of Ag2S QDSSCs’ performance. [•] Frequency-modulated SPV can supply complementary information in the study of Ag2S ODSSCs. [ABSTRACT FROM AUTHOR]

Abstract: Zn-doped TiO2 microspheres have been synthesized by introducing a trace amount of zinc nitrate hexahydrate to the reaction system. Scanning electron microscope (SEM), field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) have been utilized to characterize the samples. Both surface photovoltage spectroscopy (SPS) technique based on lock-in amplifier and transient photovoltage (TPV) measurement reveal that the slight doping of Zn can promote the separation of photo-generated charges as well as restrain the recombination due to the strong interface built-in electric field and the decreasing of surface trap states. The photovoltaic parameters of dye-sensitized solar cells (DSSCs) based on Zn-doped TiO2 are significantly better, compared to that of a cell based on undoped TiO2. The relation between the performance of DSSCs and their photovoltaic properties is also discussed. [Copyright &y& Elsevier]

Abstract: Ultrafine polyvinylpyrrolidone (PVP)/poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) composite fibers were successfully prepared by electrospinning of PVP/MEH-PPV blend solutions in solvent mixtures of 1,2-dichloroethane/chlorobenzene. Composite polymer fibers with smooth surface were obtained using solutions in which MEH-PPV''s concentration was 1.0 (wt.%). Compared with the MEH-PPV solution and bulk, PVP/MEH-PPV fibers show a significant blue shift, a stronger intensity of fluorescence and a higher surface photovoltage (SPV). The morphology of fibers has been characterized by scanning electron microscopy (SEM) and fluorescence microscopy. [Copyright &y& Elsevier]

Abstract: A one-step method was used to synthesize five hydroxylphenylporphyrin monomers with different structures [R.G. Little, J. Heterocyclic Chem. 18 (1981) 129]. They were confirmed by means of different spectroscopic analysis methods. The effects of the number and the position of the peripheral hydroxylphenyl groups of the porphyrin ring and solvents on their fluorescence spectra were discussed according to the change of the UV spectra. It was found that the fluorescence intensity was enhanced with an increase in the number of the peripheral hydroxylphenyl groups of the porphyrin ring. It was also found that the fluorescence intensity at 430nm was very weak for tetrahydroxylphenylporphyrin (TPP) and tetraphenylporphyrin (5). This phenomenon is related to the structural symmetry. The red shift of the fluorescence spectra in polar solvent DMF relative to that in CH2Cl2 can be explained on the basis of the effect of solvation. The fluorescence intensity of hydroxylphenylporphyrin 2 in DMF at 430nm is much stronger than that in CH2Cl2. The surface photovoltaic property of TPP and hydroxylphenylporphyrins 1–5 was studied by means of surface photovoltage spectra (SPS) and field induced surface photovoltage spectra (FISPS), which reveals that all the hydroxylphenylporphyrin are P-type semiconductors. The SPV spectral bands of all the hydroxylphenylporphyrins correspond to the π→π* transition. The SPS was similar to the UV–Vis spectra. It has also been found that the stronger the fluorescence intensity is, the weaker the surface photovoltage intensity is. For all the hydroxylphenylporphyrins and TPP, the surface photovoltage (SPV) of TPP is the weakest, that of hydroxylphenylporphyrin 1 is the strongest, then the SPV of the other hydroxylphenylporphyrins are gradually weakened with an increase in the number of the peripheral hydroxylphenyl groups of the porphyrin ring. This result indicates that controlling the number and position of the peripheral hydroxylphenyl substituting groups of the porphyrin ring and using different solvents could obtain the porphyrins with different electro-optical properties. [Copyright &y& Elsevier]

Abstract: The photovoltaic properties of nanoporous TiO2 film treated with Al3+ ions have been investigated by the spectral and transient photovoltage (PV) technique. The performances of the dye-sensitized solar cells (DSSCs) with different amounts of aluminum oxide were compared. The results showed that with increased amount of aluminum oxide, the spectral PV responses blue shift (with the exception of the 0.1wt%) and the time of the transient PV maximum increase. The performances of the corresponding cells were improved. These results indicated the dependence of the DSSCs performances on the charge dynamics in the corresponding nanoporous TiO2 film. [Copyright &y& Elsevier]