Interfacial engineering of CuO nanorod/ZnO nanowire hybrid nanostructure photoanode in dye-sensitized solar cell

Developing efficient and cost-effective photoanode plays a vital role determining the photocurrent and photovoltage in dye-sensitized solar cells (DSSCs). Here, we demonstrate DSSCs that achieve relatively high power conversion efficiencies (PCEs) by using one-dimensional (1D) zinc oxide (ZnO) nanowires and copper (II) oxide (CuO) nanorods hybrid nanostructures. CuO nanorod-based thin films were prepared by hydrothermal method and used as a blocking layer on top of the ZnO nanowires’ layer. The use of 1D ZnO nanowire/CuO nanorod hybrid nanostructures led to an exceptionally high photovoltaic performance of DSSCs with a remarkably high open-circuit voltage (0.764 V), short current density (14.76 mA/cm² under AM1.5G conditions), and relatively high solar to power conversion efficiency (6.18%) . The enhancement of the solar to power conversion efficiency can be explained in terms of the lag effect of the interfacial recombination dynamics of CuO nanorod-blocking layer on ZnO nanowires. This work shows more economically feasible method to bring down the cost of the nano-hybrid cells and promises for the growth of other important materials to further enhance the solar to power conversion efficiency.     

Electrochemical properties of TiO2 nanoparticle/nanorod composite photoanode for dye-sensitized solar cells

A unique composite of TiO₂ nanoparticles (NPs) and nanorods (NRs) has been used to fabricate a photoelectrode for developing dye-sensitized solar cells (DSSCs) with higher sensitivity. The TiO₂ nanorods were synthesized using a mechanical process, in which electrospun TiO₂ nanofibers was grinded in a controlled way to obtain uniform size distribution. The characteristics of electron transport, recombination lifetime and charge collection were investigated by intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS). Photoelectrodes prepared with the composites of NRs and NPs showed significant improvements in electron transportation compared to only NP photoelectrodes, which would enhance the photovoltaic performance of DSSCs. IMPS and IMVS measurements show that fast electron transport and slightly decreased recombination lifetime resulted in the improvement of efficiency. The highest energy conversion efficiency obtained from the photoelectrodes fabricated with the as-prepared rutile TiO₂ nanofibers at 5 wt% NR content was up to 6.1% under AM1.5G solar illumination. The results demonstrate that the composite nanostructure can take advantage of both the fast electron transport of the nanorods and the high surface area of the nanoparticles.     

Influence of ZnO growth temperature on the performance of dye-sensitized solar cell utilizing TiO2-ZnO composite film photoanode

Ionics - TiO2 nanoflower (NF)-ZnO composite films were synthesized by using liquid phase deposition (LPD) and dip coating method. At the lower growth temperature below 50 °C, the...     

Photovoltaic and impedance properties of dye-sensitized solar cell based on nature dye from beetroot

The present study involves fabrication and photovoltaic characterization including impedance properties of dye-sensitized solar cells based on natural dye from beetroot. The electrode of the cell was prepared with commercial Fluorine-doped Tin Oxide glass with 100 μm layer of nanostructured TiO₂ whereas, the counter electrode consisted of platinum-coated glass. Fresh juice was extracted from beetroot to use as dye. The dye exhibited high absorption in visible range. Photovoltaic measurements of the solar cell gave a short circuit current density (Jsc) of 130 μA/cm² and an open-circuit voltage (VOC) of 0.38 V under AM 1.5 illumination intensity. The VOC and Jsc showed linear behavior at higher values of illumination intensities. The conductance-voltage, the capacitance-voltage and the series resistance voltage characteristics of the dye solar cell was measured at frequency range from 5 kHz to 5 MHz to study performance of the dye-sensitized solar cells with natural dyes.     

Improvement of ZnO nanorod-based dye-sensitized solar cell efficiency by Al-doping

The current study investigates the performance of dye-sensitized solar cells (DSSCs) based on Al-doped and undoped ZnO nanorod arrays synthesized by a simple hydrothermal method. Current density-voltage (J-V) characterizations indicate that Al-doping in ZnO crystal structure can significantly improve current densities and the energy conversion efficiency (η) of ZnO nanorod-based DSSCs. The maximum η, 1.34%, was achieved in DSSC when Al-doped ZnO nanorod arrays were grown in 0.04 M zinc acetate dihydrate solution with 5 mM aluminum nitrate nonahydrate. This result represents a large increase of η in Al-doped ZnO nanorod-based DSSCs as compared to undoped (0.05%). The improved DSSC photovoltaic performance can be attributed to two main factors: (1) increased light harvesting efficiency due to a large amount of N719 adsorbed on the large surface area of Al-doped ZnO nanorod arrays, and (2) increased electrical conductivity due to A1³⁺ ion doped into the ZnO lattice at the divalent Zn²⁺ site, allowing electrons to move easily into the Al-doped ZnO conduction band.     

Oriented ZnO nanotubes arrays decorated with TiO2 nanoparticles for dye-sensitized solar cell applications

Dye-sensitized solar cells (DSSCs) based on a novel composite photoanode of TiO₂ nanoparticles coating on electrodeposited ZnO nanotube arrays are fabricated and characterized. An efficiency of 3.94 % is achieved for the composite cell, increasing 86.7 % than 2.11 % of the ZnO nanotubes cell. The short-circuit current (J _sc) and open-circuit voltage (V _oc) are also enhancing 52.9 % and 25.3 %, respectively. The improvements are because of the high surface area of TiO₂ nanoparticles, as well as fast electron transport and light scattering effect of ZnO nanotubes.     

染料敏化纳米ZnO薄膜太阳电池机理初探

讨论利用ZnO代替TiO2作为光阳极制作染料敏化薄膜太阳电池的可行性.使用LSV法，IR光谱和UV-vis光谱探讨了电池的工作机理和性能，并与染料敏化纳米TiO2薄膜太阳电池作了比较.结果发现ZnO薄膜表面与染料的吸附键合力太弱是导致ZnO太阳电池效率低下的主要原因. 关键词： 纳米ZnO 太阳电池 染料敏化 量子效率     

Hybrid photoanode films based on sparse ZnO rod array-TiO2 nanoparticles in dye-sensitized solar cells

ZnO-TiO2 hybrid photoanodes were fabricated via the doctor-blade method by integrating vertically-grown sparse ZnO arrays with hydrothermal TiO2 nanoparticles. A special surface-coating technique was developed to deposit a thin TiO2 layer on the surface of ZnO rods. Microstructure, optical and photoelectrochemical performance of the hybrid photoanodes were investigated. The denser ZnO array exhibited bad filling behavior of nanoparticles in the interspace of ZnO rods, strong scattering and low conversion efficiency (0.27%). The sparser array showed a much better integrated microstructure, improved transmittance and high conversion efficiency (2.68%). The surface modification of ZnO rods by the TiO2 thin layer was found useful in improving the interfacial microstructure between the ZnO rod and the TiO2 bulk film, and the total conversion efficiency of 3.01% was achieved, higher than that of the pure TiO2 nanoparticle cell (2.93%). The increased scattering effects on the incident light, the enhanced electron transportation at TiO2/dye/electrolyte interface, and the inhabited recombination were responsible for this improvement.     

Plasmon enhanced CdS-quantum dot sensitized solar cell using ZnO nanorods array deposited with Ag nanoparticles as photoanode

CdS-quantum dot sensitized solar cell using ZnO nanorods (ZnO NRs) array deposited with Ag nanoparticles (Ag NPs) as photoanode was fabricated. Light absorption effect of Ag NPs on improvement of the cell performance was investigated. Performance improvement of metal nanoparticles (MNPs) was controlled by the structure design and architecture. Different decorations and densities of Ag NPs were utilized on the photoanode. Results showed that using 5% Ag NPs in the photoanode results in the increased efficiency, fill factor, and circuit current density from 0.28% to 0.60%, 0.22 to 0.29, and 2.18 mA/cm² to 3.25 mA/cm², respectively. Also, incident photon-to-current efficiencies (IPCE) results showed that cell performance improvement is related to enhanced absorption in the photoanode, which is because of the surface plasmonic resonance and light scattering of Ag NPs in the photoanode. Measurements of electrochemical impedance spectroscopy revealed that hole transfer kinetics increases with introduction of Ag NPs into photoanode. Also, it is shown that chemical capacitance increases with introduction of Ag NPs. Such increase can be attributed to the surface palsmonic resonance of Ag NPs which leads to absorption of more light in the photoanode and generation of more photoelectron in the photoanode.     

Controlled repeated chemical growth of ZnO films for dye-sensitized solar cells

The controlled growth of ZnO nanorods perpendicular to substrate surface i.e. c-axis by a repeated chemical deposition method for efficient dye-sensitized solar cell application is described. X-ray diffraction study shows the wurtzite structure of ZnO with high crystallinity. Intensity and newly evolved peaks of the ZnO are found to be thickness dependent. Dye loving flower-like globular architecture of ZnO is observed after 8 μm thickness. Dye-sensitized solar cell studies show the solar-to-electrical conversion efficiency of 2.21% for 11 μm ZnO electrode when illuminated with 80 mW/cm².     

Investigation of the fill factor of dye-sensitized solar cell based on ZnO nanowire arrays

The fill factor of dye-sensitized solar cells based on the ZnO nanowire array is very low, which is usually ascribed to a rapid charge recombination. In this article, the influence on the fill factor of ZnO nanowire array cell is investigated and discussed by comparing dark current and decay rate of open circuit potential of the ZnO nanowire array cell with those of the ZnO nanoparticle cell, TiO₂ nanoparticle cell and TiO₂-coated ZnO nanowire array cell. The results demonstrate that the low fill factor of the ZnO nanowire array cell is largely caused by a rapid decrease of electron injection efficiency rather than a rapid charge recombination, which is decided by the absorption nature of Ru-complexed dye molecules on ZnO surface and repellency of radial electric field. The fill factor of the ZnO nanowire array cell can be improved by coating ZnO nanowires with a wide band gap semiconductor material or metal oxide insulator.     

Sputter-deposited ZnO thin films consisting of nano-networks for binder-free dye-sensitized solar cells

ZnO nano-network structures with high porosity were prepared for use in the photoelectrodes of binder-free dye-sensitized solar cells (DSSCs) by DC sputtering and subsequent thermal oxidation. Zn thin films prepared at 100 °C showed nano-network structures with high porosity, while those prepared at 25 °C did not. This was partially attributed to the high mobility of sputter-deposited particles that arrived at the surface of the substrate and partially to a supersaturation mechanism. The prepared nano-network Zn was successfully transformed to ZnO without a morphological change via subsequent annealing in air. The power conversion efficiency of DSSCs based on the ZnO nano-network structures exhibited 10 times higher efficiency than those based on ZnO film prepared at 25 °C because of its large surface area for adsorption of dye molecules. The thickness of the ZnO nano-network structures increased linearly at 10 μm h^?1 as a function of sputter time. As the film thickness increased, the power conversion efficiency of DSSCs increased from 1.09% to 1.82%.     

染料敏化纳米薄膜太阳电池实验研究

染料敏化纳米薄膜太阳电池（DSCs）的性能主要是由纳米多孔TiO２₂薄膜、染 料光敏化剂 、电解质、反电极（光阴极）等几个主要部分决定的.通过优化DSCs各项关键技术和材料的 性能，并通过小面积DSCs的系列实验和优化组合实验来检测各项参数对DSCs性能的影响，获 得在光照1个太阳（AM15）下，光电转换效率达到895%.这为进行产业化制备大面积DSCs 打下了良好基础. 关键词： 染料敏化 太阳电池 优化 效率     

A novel TiO2 nanoparticles/nanowires composite core with ZrO2 nanoparticles shell coating photoanode for high-performance dye-sensitized solar cell based on different electrolytes

The novel TiO₂ nanopartilces/nanowires (TNPWs) composite with ZrO₂ nanoparticles (ZNPs) shell-coated photoanodes were prepared to fabricate high-performance dye-sensitized solar cell (DSSC) based on different types of electrolytes. Hafnium oxide (HfO₂) is a new and efficient blocking layer material applied over the TNPWs-ZNPs core-shell photoanode film. TiO₂ nanoparticles (TNPs) and TiO₂ nanowires (TNWs) were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). DSSCs were fabricated using the novel photoanodes with an organic sensitizer D149 dye and different types of electrolytes namely liquid electrolyte, ionic liquid electrolyte, solid-state electrolyte, and quasi-solid-state electrolyte. The DSSC-4 made through the novel core-shell photoanode using quasi-solid-state electrolyte showed better photocurrent efficiency (PCE) as compared to the other DSSCs. It has such photocurrent-voltage characteristics: short circuit photocurrent (Jsc)?=?19 mA/cm², the open circuit voltage (Voc)?=?650 mV, fill factor (FF)?=?65 %, and PCE (η)?=?8.03 %. The improved performance of DSSC-4 is ascribed to the core-shell with blocking layer photoanode could increased electron transport and suppressed recombination of charge carriers at the TNPWs-ZNPs/dye/electrolyte interface.     

大面积染料敏化太阳电池的实验研究

通过对大面积染料敏化太阳电池的实验研究，探讨了串联电阻对大面积染料敏化太阳电池光伏特性的影响问题，给出了解决这一问题的有效方法. 在此基础上制作的大面积条状电池(0.8cm×18cm)光电转换效率达到6.89%，而由此条状电池并联组成的大面积电池(15cm×20cm)的效率接近6%. 使得大面积染料敏化太阳电池的研究工作取得突破性进展，迈出了实用化的关键一步，为其工业化生产及商业化应用提供了理论和实验依据. 关键词： 大面积 染料敏化 太阳电池 串联电阻     

Electrodeposition of zinc oxide/tetrasulfonated copper phthalocyanine hybrid thin film for dye-sensitized solar cell application

Hybrid film of zinc oxide (ZnO) and tetrasulfonated copper phthalocyanine (TSPcCu) was grown on an indium tin oxide (ITO) glass by one-step cathodic electrodeposition from aqueous mixtures of Zn(NO₃)₂, TSPcCu and KCl. The addition of TSPcCu strongly influences the morphology and crystallographic orientation of the ZnO. The nanosheets stack of ZnO leads to a porous surface structure which is advantageous to further adsorb organic dyes. The photovoltaic properties were investigated by assembling the DSSC device based on both the only ZnO film and the ZnO/TSPcCu hybrid films. Photoelectrochemical analysis revealed that the optimized DSSC device with TSPcCu represented a more than three-fold improvement in power conversion efficiency than the device without TSPcCu. The DSSC based on ZnO/TSPcCu hybrid films demonstrates an open circuit voltage of 0.308 V, a short circuit current of 90 μA cm⁻², a fill factor of 0.26, and a power conversion efficiency of 0.14%.     

Hierarchical SnO2 microspheres prepared by hydrothermal process for efficient improvement of dye-sensitized solar cell properties

Journal of Nanoparticle Research - In the present investigation, hierarchical SnO2 microspheres were synthesized by controlled hydrothermal technique. The reaction temperature was kept fixed, while...     

Analysis of electron recombination in dye-sensitized solar cell

A steady-state numerical model of dye-sensitized solar cell is based on continuity and transport equations for electrons, iodide and triiodide ions. The cell model consists of an active layer, where photovoltaic effect including diffusion of electrons in mesoporous TiO₂ and ions in electrolyte takes place, and a bulk electrolyte layer, where only ions diffuse. Exponential distribution of trap states in TiO₂ and Gaussian distributions of energy levels in the electrolyte within active layer are included in modeling of the recombination dynamics, according to Shockley-Read-Hall statistics and Marcus-Gerischer electron transfer theory. Recombinations at the front contact and a voltage drop at the platinum covered back contact are included in the model. Simulation results are compared with the measured current-voltage characteristics at different light intensities. In particular, light intensity dependence of open circuit voltage is studied over 4 decades. Optimization of cell efficiency regarding active layer and electrolyte layer thickness is carried out. Simulation results show that best efficiency is achieved when electrolyte layer thickness is minimized as much as possible and that active layer thickness is traded off with respect to recombination rates and/or diffusion limited current determined with the selection of the electrolyte.