Ruthenium dye-sensitized SnO2/TiO2 coupled solar cells

The photoelectrochemical behaviors of RuL₂(NCS)₂ dye-sensitized SnO₂/TiO₂ coupled solar cell was studied and compared with TiO₂ single system. The coupled system shows higher incident photon-to-current conversion efficiency (IPCE) value than the single system. A maximum IPCE value in the coupled system with 3.5 μm-thick SnO₂ and 7 μm-thick TiO₂ attained 82.4% at 530 nm wavelength. The higher IPCE value in the coupled system is attributed to the charge separation by fast electron transfer process from the excited RuL₂(NCS)₂ dye to TiO₂ to SnO₂ in the system with different energy level.     

Photocurrents and degradation rates on particulate TiO2 layers: Effect of layer thickness, concentration of oxidizable substance and illumination direction

Different routes for immobilization of TiO₂ on conducting substrates were compared to find active and stable photocatalysts, which could either be operated in open circuit (photocatalysis) or with applied electric potential (photoelectrocatalysis). The advantage of applying an electric potential was investigated. Polarization curves and photoelectrochemical degradation reactions served to characterize catalysts and to find a way of predicting the optimum synthesis conditions. The difference between front side (EE) and back side (SE) illumination is discussed as a function of layer thickness, as well as the influence of oxidizable substance concentration on photocurrents. Stability of catalysts was investigated in repetitive degradation experiments.     

SILAR次数对In掺杂CdS量子点敏化太阳电池的影响

以In掺杂CdS量子点太阳能电池为例,讨论了SILAR次数对In掺杂CdS量子点敏化太阳能电池性能的影响。通过SEM、EDS、IPCE、紫外吸收光谱、J-V曲线、EIS等实验测试结果表明,当In掺杂CdS的摩尔比固定在1:5时,随着SILAR次数的增加,电池的短路电流密度、开路电压和光电转换效率都随着增加,当SILAR次数为6次时,In掺杂CdS的QDSCs光电转化效率达到了最大值(η=0.76%)。随着SILAR次数的继续增加,其光电转换效率将会下降。     

Dye-sensitized solar cells: A brief overview

The aim of this brief review is to give a short and simple overview of the dye-sensitized solar cell technology from the working principles to the first commercial applications. It emphasizes the role of the sensitizer and the strategies to improve the performances of the dye as well as some recent development aiming to answer specific issues.     

Electrochemical nano-patterning of brass for stable and visible light-induced photoelectrochemical water splitting

A novel propitious nano-patterned brass oxide nanowires were fabricated via controlled anodization of α-brass in aqueous electrolytes at room temperature. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS) techniques were used to investigate the morphology, structure, and composition of the fabricated materials. The morphology of the resulted structures was found to depend on the concentration of the sodium bicarbonate used for anodization as well as the post treatment. The XRD analysis confirmed the existence of both ZnO and CuO. The XPS results suggest the formation of CuZnO nanowires. The fabricated nanowires showed exceptional optical activity with an absorption wavelength extending to 800 nm, corresponding to a bandgap energy of 1.7 eV. This bandgap energy was also confirmed via DFT calculations. The fabricated nanostructures were used to split water photoelectrochemically under AM 1.5 illumination. They showed very promising results towards visible light water splitting with a photocurrent of 1.88 mA/cm² at −0.5 V versus Ag/AgCl, an incident photon-to-current efficiency (IPCE) of ∼15% at 400 nm, and a production of ∼875 μmol of H₂ gas upon illumination for 5 h. The obtained photocurrent is at least five times higher than that reported for ZnO and TiO₂. The transient photocurrent measurements showed the fabricated electrode to be photostable under the operating conditions.     

A self‐calibrating led‐based solar test platform

A compact platform for testing solar cells is presented. The light source comprises a multi‐wavelength high‐power LED (light emitting diode) array allowing the homogenous illumination of small laboratory solar cell devices (substrate size 50 × 25 mm) within the 390–940 nm wavelength range. The spectrum can be synthesized by independent tuning of the 18 different wavelengths to mimic AM1.5G as well as various indoor lamp spectra. The intensity can be controlled with a 2¹⁴‐bit accuracy and intensities up to 3 suns are possible with an approximate AM1.5G spectral distribution. For several wavelengths intensities up to 10 suns is possible, and for a few wavelengths up to 30 suns can be reached. The setup is equipped with reference diodes and an optical fibre coupling enabling calibration, monitoring and control of the light impinging on the sample. Through a computer controlled interface, it is possible to perform all the commonly employed measurements on the solar cell at very high speed without moving the sample. In particular, the LED‐based illumination system provides an alternative to light‐biased incident photon‐to‐current efficiency measurement to be performed which we demonstrate. Both top and bottom contact is possible and the atmosphere can be controlled around the sample during measurements. The setup was developed for the field of polymer and organic solar cells with particular emphasis on enabling different laboratories to perform measurements in the same manner and obtain a common basis for comparing data. The use of the platform is demonstrated using a standard P3HT:PCBM polymer solar cell but is generally applicable to any solar cell technology with a spectral response in the 390–950 nm region. Copyright © 2010 John Wiley & Sons, Ltd.     

反应溅射条件对WO3薄膜光电性能的影响与探索

使用反应溅射法在FTO导电玻璃基底上制备了附着力强、表面光滑、均匀的WO3光电薄膜,系统地研究了氩气与氧气流量比和溅射功率对该薄膜光电性能的影响。通过XRD、AFM、Mott-Schottky(M-S)分别分析薄膜的物相、形貌、光电性质。光电转化效率(IPCE)测试表明:当氩氧流量比为2和溅射功率250 W时,WO3薄膜的光电性能最好。该薄膜在400 nm波长处的IPCE值高达40%。     

Synthesis and photovoltaic properties of an alternating phenylenevinylene copolymer with substituted-triphenylamine units along the backbone for bulk heterojunction and dye-sensitized solar cells

We have fabricated bulk heterojunction (BHJ) photovoltaic devices based on the as cast and thermally annealed P:[6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) blends and found that these devices gave power conversion efficiency (PCE) of about 1.15 and 1.60% respectively. P is a novel alternating phenylenevinylene copolymer which contains 2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid units along the backbone and was synthesized by Heck coupling. This copolymer was soluble in common organic solvents and showed long-wavelength absorption maximum at 390-420 nm with optical band gap of 1.94 eV. The improvement of PCE after thermal annealing of the device based on the P:PCBM blend was attributed to the increase in hole mobility due to the enhanced crystallinity of P induced by thermal treatment. In addition, we have fabricated BHJ photovoltaic devices based on the as cast and thermally annealed PB:P:PCBM ternary blend. PB is a low band gap alternating phenylenevinylene copolymer with BF₂-azopyrrole complex units, which has been previously synthesized in our laboratory. We found that the device based on this ternary blend exhibited higher PCE (2.56%) as compared to either P:PCBM (1.15%) or PB:PCBM (1.57%) blend. This feature was associated with the well energy level alignment of P, PB and PCBM, the higher donor-acceptor interfaces for the exciton dissociation and the improved light harvesting property of the ternary blend. The further increase in the PCE with thermally annealed ternary blend (3.48%) has been correlated with the increase in the crystallinity of both P and PB. Finally, we used copolymer P as sensitizer for quasi solid state dye-sensitized solar cell and we achieved PCE of approximately 3.78%.     

Direct solar water splitting cell using water, WO3, Pt, and polymer electrolyte membrane

A solar water splitting cell composed of WO₃, Polymer Electrolyte Membrane (PEM) and Pt was constructed for producing hydrogen from deionized water in sunlight. Spectral responsivity measurements under various temperatures and bias voltages were conducted for the cell using the Incident Photon to Current Efficiency (IPCE) method. For comparison, a known WO₃ Photo Electro Chemical (PEC) cell containing H₃PO₄ electrolyte, WO₃/H₃PO₄/Pt, was tested using the same test method. The WO₃/PEM–H₂O/Pt cell showed better Quantum Efficiency (QE) performance compared to that obtained from the cell with the chemical electrolyte. For the first time, spectral responsivity of photo water splitting process without bias power was unveiled in the new WO₃ cell, demonstrating the self-sustained photo electrolysis capability. Bias voltage effect on Solar to Hydrogen (STH) conversion efficiency was dramatic in the range from 0.2 V to 1.2 V and suppressions of STH were observed when high bias voltages were applied. In addition, a strong temperature effect on the energy conversion efficiency at high bias voltage was observed in the cell containing PEM–H₂O, revealing that the STH at 54 °C is nearly five times that at 14 °C.     

Ge-doped ZnO nanorods grown on FTO for photoelectrochemical water splitting with exceptional photoconversion efficiency

In this study, a considerable effort has been devoted for the synthesis of Ge-doped ZnO nanorods on FTO as an efficient and robust photoanode material for solar water splitting. A unique, optimized, and ultra-rapid fabrication method to produce uniform nanorods (30–70 nm in diameter) has been demonstrated using radio frequency sputtering followed by electrochemical anodization. The effect of Ge doping on the conductivity, charge carrier concentration, optical, and photoelectrochemical properties of ZnO was investigated using scanning electron microscope (SEM), glancing angle X-ray diffraction (GAXRD), UV–Vis spectrometer, and Mott Schottky analysis. Glancing angle XRD confirmed the presence of wurtzite structure with a preferable orientation around (101) plane, which is of particular interest for many applications. As evidenced by the photoelectrochemical and transient photocurrent measurements, the fabricated Ge-doped ZnO nanorods exhibited enhanced photocurrent (12 mA/cm²) with an exceptional open circuit voltage of ?1.07 V_SCE (?0.416 V_RHE) under AM1.5G illumination, compared to the undoped ZnO based-photoanodes. Moreover, the Ge-doped ZnO nanorods showed unprecedented photoconversion efficiency of 3.6% under AM1.5G illumination. Therefore, the fabricated Ge-doped ZnO nanorods could be a promising conductive photoanode for water splitting.