Extraction and application of natural pigments for fabrication of green dye-sensitized solar cells

Four dye-sensitized solar cell devices are designed and fabricated based on natural dyes extracted from Celosia Cristata, Saffron, Cynoglossum, and eggplant peel, as photosensitizers. The UV–vis technique has been served to determine maximum absorption of natural extract and pre-dyed photoanode. The Fourier transform infrared (FT-IR) was employed to cover the presence of functional groups. The cyclic voltammetry method has been employed to assess the possibility of charge transfer from dried natural dyes to the photoelectrode. The performance of natural-based dye-sensitized solar cells is determined subsequently. The highest power conversion efficiency was ca. 1.38%, which belonged to Celosia Cristata extract. The devices were examined for higher efficiencies, individually, co-sensitized arrangement and/or in tandem with each other.     

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.     

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.     

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.     

TiO2 treatment using ultrasonication for bubble cavitation generation and efficiency assessment of a dye-sensitized solar cell

In this study, the impacts of different ultrasonic treatments on TiO₂ particles were determined and they were used to manufacture the photoelectrodes of a dye-sensitized solar cell (DSSC). Two methods were used to prepare TiO₂ particles directly sonicated by an ultrasonic horn, and TiO₂ treated indirectly by an ultrasonic cleaner. TEM, XPS analysis was confirmed that cavitation bubbles generated during ultrasonication resulted in defects on the surface of TiO₂ particles, and the defect induced surface activation. To understand the effect of TiO₂ surface activation on energy conversion efficiency of DSSC, ultrasonic horn DSSC and ultrasonic cleaner DSSC were prepared. The UV–vis analysis exhibited that the ultrasonic horn DSSC possessed higher dye adsorption when compared to the ultrasonic cleaner DSSC, and the EIS analysis confirmed that the electron mobility was greatly increased in the ultrasonic horn DSSC. The energy conversion efficiency of the ultrasonic horn DSSC was measured to be 3.35%, which is about 45% increase in comparison to that of the non-ultrasonic treated DSSC (2.35%). In addition to this regard, recombination resistance of ultrasonic horn DSSC was calculated to be 450 Ω·cm², increasing more than two times compared to the non-ultrasonic treated DSSC (200 Ω·cm²). Taken together, these ultrasonic treatments significantly improved the energy conversion efficiency of DSSC, which was not tried in DSSC-related research, and might lead us to develop more efficient practical route in the manufacturing of DSSC.     

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     

Characterization of nanocrystalline SnO2 thin film fabricated by electrodeposition method for dye-sensitized solar cell application

Nanocrystalline SnO₂ thin film was prepared by cathodic electrodeposition-anodic oxidation and its structure was characterized by X-ray diffraction, SEM, UV-visible absorption and nitrogen adsorption-desorption by BET method. The obtained film has a surface area of 137.9 m²/g with grain sized of 24 nm. Thus the prepared SnO₂ thin film can be applied as an electrode in dye-sensitized solar cell. The SnO₂ electrode was successfully sensitized by Erythrosin dye and photoelectrochemical measurements indicate that the cell present short-circuit photocurrent (J_sc) of 760 μA/cm², fill factor (FF = 0.4), photovoltage (V_oc = 0.21 V) and overall conversion efficiency (η) of 0.06% under direct sun light illumination. The relatively low fill factor and photovoltage are attributed to the reduction of triodiode by conduction band electrons and intrinsic properties of SnO₂.     

Ultrasonic irradiation preparation of graphitic-C3N4/polyaniline nanocomposites as counter electrodes for dye-sensitized solar cells

In this research, polyaniline/graphitic carbon nitride (PANI/g-C₃N₄) nanocomposites were synthesized via in-situ electrochemical polymerization of aniline monomer whit different number of cyclic voltammetry scans (10, 20 and 30 cycles) after electrode surface pre-preparation using a potential shock under ultrasonic irradiation. PANI/g-C₃N₄ nanocomposites with two values of g-C₃N₄ (0.010 wt% and 0.015 wt%) were deposited on the surface of the transparent conducting film (FTO glass) by immersing FTO into the aniline solution and g-C₃N₄ during the electro-polymerization. The resulting PANI/g-C₃N₄ films were characterized by Fourier transformed infra-red (FTIR), power X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) techniques. The prepared electrodes were applied as counter electrode in dye-sensitized solar cells. Among them, the prepared electrode with 10 cycles and 0.01 wt% g-C₃N₄ showed the best efficiency. These hybrids show good catalytic activity in elevating tri-iodide reduction and due to the synergistic effect of PANI and g-C₃N₄, PANI/g-C₃N₄ nanocomposite electrode shows power conversion efficiency about 1.8%.     

Ni3S2@MWCNTs films for effective counter electrodes of dye-sensitized solar cells

Composite films nickel sulfide (Ni₃S₂) nanoparticles were grown on multiwall carbon nanotubes (MWCNTs) and in situ coated onto conducting glass substrates by the hydrothermal process at 170 °C. These Ni₃S₂@MWCNTs films were applied for counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). In this work, nanostructure, crystalline structure, electrochemical activities and electron-charge transfer resistance of CEs were studied. In addition, the effective surface areas of CEs were analyzed and discussed as well. The power conversion efficiency (PCE) enhancement of up to 7.48%, compared with that of Ni₃S₂-DSSC, was demonstrated for a Ni₃S₂@MWCNTs DSSC.     

An investigation of DNA-like structured dye-sensitized solar cells

This paper reports a 3D DNA-like structured dye-sensitized solar cell (DSSC) with all-Ti substrates. A self-organized TiO₂ nanotubular arrays layer was directly grown on the photoanode surface by electrochemical anodization. Compared with the traditional flat-type DSSC, the DNA-like DSSC showed superiority of light utilization due to its symmetrical double-helix structure. Different thickness of the nanotubular arrays layers were investigated to find their influence on the cell’s photovoltaic parameters, and the cell with a 15.3 μm layer exhibited the highest P_max, about 0.49 mW. The series–parallel connection characteristics of the DNA-like DSSCs reveal that the total voltage and the total short current equalled the sum of each cell’s in series and in parallel, respectively. It is anticipated that the novel DNA-like structured DSSCs have great application potential in larger modules using integrated circuit.     

Influence of thermal effect on the efficiency of a solar cell

The short-circuit current and open-circuit voltage of a solar cell based on the p-n junction are studied theoretically, taking into account the thermoemf originating due to the temperature difference between the front and back surfaces of the solar cell. It is shown that the consideration of the thermal motion of photogenerated carriers leads to the increase in the collection coefficient. Calculations show that at the irradiation intensity 5 × 10²⁰ photon/cm² s and at the temperature gradient ～ 30–40°C for silicon solar cells the open circuit voltage increases by ～ 6–7% and the short circuit current by ～40–50%.     

Effect of dispersing media on microstructure of electrophoretically deposited TiO2 nanoparticles in dye-sensitized solar cells

In the present study, dye-sensitized solar cells were fabricated using electrophoretically deposited layers of titanium dioxide nanoparticles from two common organic media, acetone and isopropanol. Characterization of the obtained layers by scanning electron microscope and atomic force microscope showed that a non-uniform porous layer was obtained in acetone; however, deposition from the titanium dioxide/isopropanol cell resulted in the formation of a relatively uniform microstructure. Ultraviolet-visible (UV-vis) spectra of adsorbed dye on the two layers show that more dye is loaded on the layer deposited in acetone. Current-voltage characteristics of the cells indicate that for the case of the cells made by the layer formed in acetone, the internal resistance of the cell is more than that of isopropanol medium which would decrease the efficiency of the cell. This difference was attributed to the reduction of effective surface area and also the loss of particles interconnection as a result of the presence of aggregates within the layer obtained in acetone.     

大面积染料敏化太阳电池的串联阻抗特性研究

在电子扩散微分方程的基础上,研究了染料敏化太阳电池光生电流和光生电压随光照强度不同的变化关系.提出敏化太阳电池串联阻抗功率损耗模型,理论模拟了大面积电池（有效面积>1 cm²）光电转换效率随多孔薄膜有效面积宽度变化的曲线、透明导电基底膜与银栅极的比接触电阻以及在不同入射光强下银栅极体电阻对大面积染料敏化太阳电池光伏性能的影响.结果表明透明导电基底膜的方块电阻和银栅极体电阻对大面积染料敏化太阳电池的性能有很大影响,而这种影响随光强的减弱逐渐减小. 关键词： 染料敏化 太阳电池 串联阻抗 光电转换效率     

First-principles study on Sb-doped SnS2 as a low cost and non-toxic absorber for intermediate band solar cell

Tin disulfide has attracted much attention on solar cell study due to its excellent optoelectronic properties in addition to just containing low-cost and non-toxic elements. Based on the HSE06-hybrid function calculations combined with Grimme's dispersion-correction method, a half-filled and delocalized intermediate band(IB) is presented in the main band gap of SnS₂ after partially Sb substituting on Sn site, which is made of the antibonding states of Sb-s and S-p states. Three-photon absorption can be realized in the doped sample and its corresponding absorption coefficient is enhanced at the visible light region thanks to the isolated and half-filled IB above the original valence band. Furthermore, Sb_Sn always has the lowest formation energy than other Sb-related defects (i.e. Sb_S and Sb_i) based on the defect formation energy calculations. Therefore, Sb-doped SnS₂ is suggested as a promising candidate for the absorber of intermediate band solar cell.     

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.     

XPS characterization of sensitized n-TiO2 thin films for dye-sensitized solar cell applications

TiO₂ thin films, employed in dye-sensitized solar cells, were prepared by the sol-gel method or directly by Degussa P25 oxide and their surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The effect of adsorption of the cis-[Ru(dcbH₂)₂(NCS)₂] dye, N3, on the surface of films was investigated. From XPS spectra taken before and after argon-ion sputtering procedure, the surface composition of inner and outer layers of sensitized films was obtained and a preferential etching of Ru peak in relation to the Ti and N ones was identified. The photoelectrochemical parameters were also evaluated and rationalized in terms of the morphological characteristics of the films.     

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     

Performance of conversion efficiency of a bifacial silicon solar cell with particle irradiation

This paper investigates theoretically the performance of conversion efficiency of a bifacial silicon solar cell with particle irradiation. The bifaciality coefficient and the conversion efficiency are calculated for various rear side illumination conditions and electron fluence, taking into account the diffusion length related damage coefficient. The main purpose of the work is to show that irradiation could significantly degrade both the bifaciality coefficient and then the conversion efficiency of the bifacial solar cell and to exhibit the role of the fluence and rear side illumination condition level in the performance of the bifacial silicon solar cell.