Zheng-Ji Zhou

One-step synthesis of stoichiometric Cu2ZnSnSe4 as counter electrode for dye-sensitized solar cells.

Cu(2)ZnSnSe(4) (CZTSe) nanoparticles with diameters of 200-300 nm were synthesized by one-step solvothermal method without surfactants or templates. The structure, composition and morphology of CZTSe nanoparticles were characterized by XRD, XPS, Raman spectrum, EDS, FESEM and TEM. The results indicated that the nanoparticles were single phase and nearly stoichiometric composition. CZTSe nanoparticles drop-casted onto FTO substrate were used as counter electrode (CE) in dye-sensitized solar cells (DSSCs) for the first time, which exhibited Pt-like electrocatalytic activity for the reduction of I(3)(-) to I(-) in DSSCs. The J-V results demonstrated that the thickness of the film affected the photocurrent density and fill factor remarkably, which resulted from the difference of electrocatalytic sites and resistance with different thickness films. And a best efficiency of 3.85% was obtained by adjusting the film thickness. The work presents a new approach for developing low-cost, facile fabrication CZTSe nanoparticles, and demonstrates CZTSe can be explored as a low-cost alternative for expensive and scare Pt in DSSCs.

Surfactant-Free CuInS2 Nanocrystals: An Alternative Counter-Electrode Material for Dye-Sensitized Solar Cells

Surfactant-free CuInS2 (CIS) nanocrystals (NCs) were synthesized by replacing organic capping ligands with inorganic ions S(2-). The efficacy of ligand exchange was probed by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis spectroscopy, and Fourier-transform infrared (FTIR). The surfactant-free CIS NCs films were obtained by drop-casting onto the clean FTO glass. The electrical conductivity and electrocatalytic activity of CIS NCs films were sharply increased due to the improved interparticle coupling after ligand exchange. When the surfactant-free CIS films were used as counter electrode (CE) in dye-sensitized solar cells (DSSCs), a conversion efficiency of η = 5.77% was achieved without sintering.

Effect of Highly Ordered Single-Crystalline TiO2 Nanowire Length on the Photovoltaic Performance of Dye-Sensitized Solar Cells

One-dimensional semiconductor nanostructures grown directly onto transparent conducting oxide substrates with a high internal surface area are most desirable for high-efficiency dye-sensitized solar cells (DSSCs). Herein, we present a multicycle hydrothermal synthesis process to produce vertically aligned, single crystal rutile TiO(2) nanowires with different lengths between 1 and 8 μm for application as the working electrode in DSSCs. Optimum performance was obtained with a TiO(2) nanowire length of 2.0 μm, which may be ascribed to a smaller nanowire diameter with a high internal surface area and better optical transmittance with an increase in the incident light intensity on the N719 dye; as well as a firm connection at the FTO/TiO(2) nanowire interface.

Solution Fabrication and Photoelectrical Properties of CuInS2 Nanocrystals on TiO2 Nanorod Array

One-dimensional semiconductor architectures are receiving attention in preparing photovoltaic solar cells because of its superior charge transport as well as excellent light-harvesting efficiency. In this study, vertically aligned single-crystalline TiO(2) nanorods array was grown directly on transparent conductive glass (FTO), and then CuInS(2) nanocrystals were deposited on nanorods array by spin coating method to form TiO(2)/CuInS(2) heterostructure films. The resulting nanostructure assembly and composition was confirmed by field-emission scanning electron microscope (FESEM) , transmission electron microscopy (TEM), high-resolution TEM, and X-ray diffraction(XRD). Ultraviolet-visible absorption spectroscopy (UV-vis) data indicates that the absorbance of the nanocomposite film extended into the visible region compared with bare TiO(2) nanorod arrays. The surface photovoltage spectra (SPS) also showed a new and enhanced response region corresponding to the absorption spectrum. These results suggest that the novel CuInS(2) nanocrystals sensitized TiO(2) nanorod array on FTO photoelectrodes has a potential application in photovoltaic devices.

Enhanced Performance of Dye‐Sensitized Solar Cells Using Solution‐Based In Situ Synthesis and Fabrication of Cu2ZnSnSe4 Nanocrystal Counter Electrode

On the bright side: A solution-based strategy was developed for in situ synthesis and film deposition of Cu2ZnSnSe4 nanocrystal films (samples a-d). The obtained Cu2ZnSnSe4 nanocrystal films can be used as an effective counter-electrode (CE) material to replace Pt, and yield low-cost, high-efficiency dye-sensitized solar cells (DSSCs). The assembled solar cell devices exhibit an efficiency of 7.82 % under 1 sun irradiation (see figure).

CuInS2 quantum dot-sensitized TiO2 nanorod array photoelectrodes: synthesis and performance optimization

CuInS2 quantum dots (QDs) were deposited onto TiO2 nanorod arrays for different cycles by using successive ionic layer adsorption and reaction (SILAR) method. The effect of SILAR cycles on the light absorption and photoelectrochemical properties of the sensitized photoelectrodes was studied. With optimization of CuInS2 SILAR cycles and introduction of In2S3 buffer layer, quantum dot-sensitized solar cells assembled with 3-μm thick TiO2 nanorod film exhibited a short-circuit current density (Isc) of 4.51 mA cm−2, an open-circuit voltage (Voc) of 0.56 V, a fill factor (FF) of 0.41, and a power conversion efficiency (η) of 1.06%, respectively. This study indicates that SILAR process is a very promising strategy for preparing directly anchored semiconductor QDs on TiO2 nanorod surface in a straightforward but controllable way without any complicated fabrication procedures and introduction of a linker molecule.

Effect of Crystallization of Cu2ZnSnSxSe4–x Counter Electrode on the Performance for Efficient Dye-Sensitized Solar Cells

Cu2ZnSnSxSe4-x (CZTSSe) counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) are commonly developed with porous structures, but their high surface area could also retard electron transport processes owing to the abundant grain boundaries. Herein, we employed a convenient solution method and a rapid heating process to prepare well crystalline CZTSSe CEs in DSSCs. The influence of crystallization of CZTSSe film on DSSCs performances was discussed in depth. The thermogravimetric analysis, phase morphology, conductivity, and electrochemical characteristics of CZTSSe films were performed. It is found that the rapid heating process is beneficial to the formation of well crystalline film with large grains. As the porosity and grain boundaries in the bulk film are dramatically reduced with the enhanced crystallization, the charge transport process is gradually improved. Using cyclic voltammogram and electrochemical impedance spectroscopy measurements, we propose that the accelerating charge transport is of great importance to the photovoltaic performances of DSSCs due to their superior electrocatalytic activities. As the highest cell efficiency was achieved, well crystalline CZTSSe is an efficient CE catalytic material.

Wurtzite copper-zinc-tin sulfide as a superior counter electrode material for dye-sensitized solar cells

Wurtzite and kesterite Cu2ZnSnS4 (CZTS) nanocrystals were employed as counter electrode (CE) materials for dye-sensitized solar cells (DSSCs). Compared to kesterite CZTS, the wurtzite CZTS exhibited higher electrocatalytic activity for catalyzing reduction of iodide electrolyte and better conductivity. Accordingly, the DSSC with wurtzite CZTS CE generated higher power conversion efficiency (6.89%) than that of Pt (6.23%) and kesterite CZTS (4.89%) CEs.

Solution-deposited pure selenide CIGSe solar cells from elemental Cu, In, Ga, and Se

A novel, robust and low-toxicity solution route to deposit CIGSe thin films for solar cell applications is proposed. The solvent mixture of 1,2-ethanedithiol and 1,2-ethylenediamine is employed for the first time to simultaneously dissolve elemental Cu, In, Ga, and Se, forming the CIGSe precursor solution. With this solution-processed CIGSe thin film solar cell, a power conversion efficiency of 9.5% has been achieved.

p-type Li, Cu-codoped NiOx hole-transporting layer for efficient planar perovskite solar cells

p-type inorganic hole transport materials of Li, Cu-codoped NiOx films were deposited using a simple solution-based process. The as-prepared films were used as hole selective contacts for lead halide perovskite solar cell. An enhanced power conversion efficiency of 14.53% has been achieved due to the improved electrical conductivity and optical transmittance of the Li, Cu-codoped NiOx electrode interlayer.