Photovoltaic Performance Of Dye-sensitized Solar Cells Research Articles

Improvement in Long-Term Stability and Photovoltaic Performance of UV Cured Resin Polymer Gel Electrolyte for Dye-Sensitized Solar Cell

We introduced a new UV-cured resin polymer gel as an electrolyte for dye-sensitized solar cells (DSSCs) that is cured with UV irradiation to form a thin film of UV-cured resin polymer gel in the cells. The gel film was characterized and its potential for use as an electrolyte in DSSCs was investigated. This new UV-cured resin polymer gel was successfully applied as a gel polymer electrolyte in DSSCs overcoming the problems associated with the liquid electrolytes in typical DSSCs. The effect of γ-butylrolactone (GBL) on the long-term stability and photovoltaic performance in DSSCs using this UV-cured resin polymer gel electrolyte was also investigated. The results of the energy conversion efficiency, ionic conductivity and Raman spectra of the UVcured resin polymer gel electrolyte with the addition of 6 wt % GBL to the UV-cured resin polymer electrolyte showed good long-term stability and photovoltaic performance for the DSSCs with the UV-cured polymer gel electrolyte.

Extension lifetime for dye-sensitized solar cells through multiple dye adsorption/desorption process

In this study, we propose a novel concept of extending the lifetime of dye-sensitized solar cells (DSCs) and reducing the costs of re-conditioning DSCs by recycling the FTO/TiO2 substrates. The photovoltaic performances of DSCs using substrates with various cycles of dye uptake and rinse off history are tested. The results show that dye adsorption and Voc are significantly increased under multiple dye adsorption/desorption process and resulted in the improvement of power conversion efficiency. Moreover, the dyeing kinetics is faster after multiple recycling processes, which is favorable for the industrial application. With surface analysis and charge transport characteristics, we also demonstrate the optimal functionality of TiO2/dye interface for the improved Voc and efficiency. The results confirm that the improved performances are due to increased dye loading and dense packing of dye molecules. Our results are beneficial for the understanding on the extension of DSCs lifetime after long-term operation in the application of DSC modules. This approach may also be applied in the replacement of newly synthesized photosensitizes to the active cells.

Photovoltaic performance of bifacial dye sensitized solar cell using chemically healed binary ionic liquid electrolyte solidified with SiO2 nanoparticles

In this study, we investigated the effect of electrolyte composition, photoanode thickness, and the additions of GuSCN (guanidinium thiocyanate), NMB (N-methylbenimidazole), and SiO2 on the photovoltaic performance of DSSCs (dye sensitized solar cells). A bifacial DSSC is realized and irradiated from front and rear sides. The devices give maximum photovoltaic efficiencies for 70% PMII (1-propyl-3-methyl-imidazolium iodide)/30% (EMIB(CN)4) (1-ethyl-3-methyl-imidazolium tetracyanoborate) electrolyte composition and 10μm thick photoanode coating which is considered to be the ideal coating thickness for the diffusion length of electrolyte and dye absorption. A significant increase in the photocurrent for DSSCs with optimum molarity of 0.1M GuSCN was observed due to decreased recombination which is believed to be surface passivation effect at photoanode electrolyte interface suppressing recombination rate. Moreover, optimum NMB molarity was found to be 0.4 for maximum efficiency. Addition of SiO2 to the electrolyte both as an overlayer and dispersed particles enhanced rear side illuminated cells where dispersed particles are found to be more efficient for the front side illuminated cells due to additional electron transport properties. Best rear side illuminated cell efficiency was 3.2% compared to front side illuminated cell efficiency of 4.2% which is a promising result for future rear side dye sensitized solar cell applications where front side illumination is not possible like tandem structures and for cells working from both front and rear side illuminations.

Enhancing photovoltaic performance of dye-sensitized solar cells by using thermally decomposed mirror-like Pt-counter electrodes

This article presents the fabrication of a homogeneous mirror-like Pt-counter electrodes and its utilization in dye-sensitized solar cells (DSSCs). The homogeneous Pt-counter electrodes were fabricated through modified thermal decomposition method by adding a suitable amount of polyvinyl pyrrolidone (PVP) in a high concentration of Pt precursor solution. The micro-morphology of prepared Pt-counter electrodes was compared with those prepared by traditional thermal decomposition and electrochemical deposition methods. The different preparation methods showed obvious influence on the micro-morphologies of Pt-counter electrodes, which further influence the catalytic activity for iodide/tri-iodide redox reaction and hence the photovoltaic performance of DSSCs. A remarkable enhancement in the photovoltaic performance of the DSSCs was achieved by the application of the prepared Pt-counter electrodes through the modified thermal decomposition method. Moreover, an obvious improvement in the reflectance properties of the prepared Pt-counter electrodes was observed, which plays an important contribution in the enhancement of the photovoltaic performance of the DSSCs.

Influence of the Anchoring Modes on the Electronic and Photovoltaic Properties of D−π–A Dyes

Five new donor−π-bridge−acceptor (D−π−A) organic sensitizers with cyano and/or triple bond substituted benzoic acid as acceptor/anchoring groups were synthesized and tested for their performance in dye-sensitized solar cells (DSCs). The systematic incorporation of a cyano group on the benzoic acid anchoring part and an additional acetylene bond at the para-position to −COOH lead to a variation of the photoelectrochemical properties, electronic transitions, and device performances. Characterization of the molecular structure, the electronic/optical properties of the dyes, as well as their photovoltaic performance in DSCs was accomplished by means of electrochemistry, quantum chemical methods, and various spectroscopic techniques such as photoinduced absorption, steady-state spectroscopy, and time-resolved transient absorption studies on femto- and nanosecond time scales. Thereby, significant dependence of DSCs performances on the substituents and anchoring groups was observed. In general, cyano substituents lead to improved DSCs performances. On the other hand, the insertion of an acetylene linker in combination with a cyano group does not enhance the device efficiencies. Devices composed of a para-cyano benzoic acid as anchor revealed maximum IPCE values of 80% with a PCE of 4.50% at AM 1.5 G illumination (100 mW cm −2 ) due to retarded charge recombination dynamics.

Preparation of composite light-scattering layer for dye sensitized solar cells

In this work, the dye sensitized solar cells (DSSCs) were fabricated with bilayered structure TiO2 based photoelectrodes, active and composite light scattering layers. The photoconversion efficiencies of these cells were significantly greater than those of the cells made by single active layered TiO2 films. The composite scattering layers consist of mixed commercial TiO2 particles (ST41) and anatase TiO2 nanoparticles (NPs). The effect of scattering layer composition (ST41:NP weight ratio) on the photovoltaic performance of DSSCs has also been investigated. The best photoconversion efficiency of DSSC was 9.02% (open circuit voltage (Voc)=0.76V, short-circuit photocurrent density (Jsc)=17.6mA/cm2, fill factor (FF)=0.68) for ST41+NP cell (40% ST41 and 60% NPs) with the TiO2 film thickness of 15.3μm, which was 58% enhancement compared with the TiO2 film without scattering-layered TiO2. The scattering layer effect was vindicated by the incident photon-to-current conversion efficiency measurement.

Morphology controllable fabrication of Pt counter electrodes for highly efficient dye-sensitized solar cells

The thermal decomposition method is usually used for fabricating Pt counter electrodes for dye-sensitized solar cells (DSSCs). The limitation of the method is its little control over the Pt particle size, agglomeration of the Pt particles on the conductive substrate and poor uniformity of the Pt counter electrodes. Herein, homogeneously dispersed Pt particles on FTO conductive glasses were prepared with an improved thermal decomposition method through adding a small amount of polyvinyl pyrrolidone (PVP) in the Pt precursor solution. The different additional amounts of PVP in the Pt precursor solution could influence the morphologies of the Pt counter electrodes, which further influenced the catalytic activity of the Pt counter electrodes and the photovoltaic performance of DSSCs. An enhanced energy conversion efficiency of the DSSC of about 8.394% was obtained when the Pt counter electrode was prepared with the additional weight amount of PVP 3.5 times that of H2PtCl6·6H2O in the Pt precursor solution, obviously higher than the original 7.062% value of the DSSC with the Pt counter electrode prepared by the traditional unmodified thermal decomposition method on the same loaded low weight of 3.765 μg cm−2.

Photovoltaic Performance of Dye-Sensitized Solar Cells Based on Al-Doped TiO<sub>2</sub> Thin Films

Al-doped TiO2 thin films were synthesized by the hydrothermal method. To prepare a working electrode, a TiO2 or AlTiO2 slurry was coated onto a fluorine-doped tin oxide glass substrate by the doctor blade method and the coated substrate was sintered at 450 ° C. TiO2 and Al-doped TiO2 films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and tested by the dye-sensitized solar cell (DSSCs) system. The influences of Al-doping on TiO2 crystal form and the photovoltaic performance of DSSCs were investigated. X-ray photoelectron spectroscopy (XPS) data indicate that the doped Al ions exist in the form of Al , and these ions play a role as e or h + traps and reduce the e/h + pair recombination rate. The corresponding MottSchottky plot indicates that the Al-doped TiO2 photoanode shifts the flat band potential positively. The positive shift of the flat band potential improves the driving force of injected electrons from the LUMO of the [Article] doi: 10.3866/PKU.WHXB201112161 www.whxb.pku.edu.cn 物理化学学报(Wuli Huaxue Xuebao) Acta Phys. -Chim. Sin. 2012, 28 (3), 591-595 March Received: October 26, 2011; Revised: December 13, 2011; Published on Web: December 16, 2011. ∗Corresponding authors. ZHOU Yang, Email: Yzhou@bjtu.edu.cn; Tel: +86-10-51685554. LIN Yuan, Email: liuyuan@iccas.ac.cn; Tel: +86-10-82615031. The project was supported by the National Key Basic Research Program of China (973) (2006CB202605), National High-Tech Research and Development Program of China (863) (2007AA05Z439), and National Natural Science Foundation of China (20973183). 国家重点基础研究发展规划项目(973) (2006CB202605),国家高技术研究发展计划项目(863) (2007AA05Z439)及国家自然科学基金项目 (20973183)资助 C Editorial office of Acta Physico-Chimica Sinica 591 Acta Phys. -Chim. Sin. 2012 Vol.28 dye to the conduction band of TiO2. The Al-doped TiO2 thin film shows a photovoltaic efficiency of 6.48%, which is higher than that of the undoped TiO2 thin film (5.58%) and the short-circuit photocurrent density increases from 16.5 to 18.2 mA·cm-2.

UV-Assisted Chemical Sintering of Inkjet-Printed TiO2 Photoelectrodes for Low-Temperature Flexible Dye-Sensitized Solar Cells

We have investigated the UV-assisted chemical (UV-Chemical) sintering of inkjet-printed TiO2 photoelectrode films for the fabrication of low temperature flexible dye-sensitized solar cells (DSSCs). A titanium organic compound as a chemical sintering source was introduced to an ink where TiO2 nanoparticles were dispersed. The formulated ink was printed by inkjet to prepare TiO2 photoelectrodes for DSSCs. The UV irradiation on the inkjet-printed photoelectrode led to the photodecomposition of the titanium organic compound at 150°C, resulting in the formation of new TiO2 among the TiO2 nanoparticles in the photoelectrode. The newly formed TiO2 enhanced the connectivity among TiO2 nanoparticles in the photoelectrode. The microstructure of TiO2 photoelectrode was investigated both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) in order to verify the effect of the UV-Chemical sintering on TiO2 interparticle connectivity. The photovoltaic performance of DSSCs with the UV-Chemical sintered TiO2 photoelectrodes was characterized by incident photon-to-current conversion efficiency (IPCE) and electrochemical impedance analysis. Based on this learning, flexible DSSC was also fabricated on the plastic substrate. This study suggests that UV-assisted chemical sintering offers a feasible opportunity to fabricate low-temperature flexible DSSC.

Influence of Polymer Gel Electrolyte on the Performance of Dye-Sensitized Solar Cells Analyzed by Electrochemical Impedance Spectroscopy

The effects of gel electrolyte polymer matrix structure and composition on the photovoltaic properties of quasi-solid state dye-sensitized solar cells(DSSCs) were investigated using two series of copolymers,poly(hydroxy ethyl methacrylate-N-vinyl) pyrrolidone P(HEMA-NVP) and poly(methyl methacrylateN-vinyl pyrrolidone) P(MMA-NVP),by electrochemical impedance spectroscopy(EIS).P(HEMA-NVP) copolymers with various crosslinking agent and N-vinyl pyrrolidone(NVP) contents,as well as P(MMA-NVP)copolymers with various NVP content,absorbed liquid electrolyte to form gel electrolytes HGelI,HGelII,and MGel,respectively.It was found that with increasing copolymer P(HEMA-NVP) crosslinking agent content,from 0.1 to 0.6%(w),the power conversion efficiency(η) of DSSCs based on HGelI initially increased and then decreased.A maximum conversion efficiency of 5.54% at 100 mW.cm-2 was observed when crosslinker content was 0.4%(w).Meanwhile,we compared the parameters of DSSCs based on HGelII with those of DSSCs based on MGel.The conversion efficiencies of the former,which contained hydroxy groups,were all higher than those of the latter,while the open circuit voltages(Voc) of the latter were larger than those of the former.DSSCs assembled with HGelII with a HEMA content of 60% exhibited the highest conversion efficiency,at 100 mW.cm-2.Electrochemical impedance spectroscopy(EIS) investigations showed that copolymer crosslinking structure affected the internal resistance and ionic conductivity of the resulting DSSCs,while addition of hydroxy groups decreased the interfacial resistance.Thus,the photovoltaic performance of DSSCs can be improved by tuning the crosslinking structure and the hydroxy content of the copolymer.

Synergistic effect of molybdenum nitride and carbon nanotubes on electrocatalysis for dye-sensitized solar cells

As a counter electrode for dye-sensitized solar cells (DSSCs), MoN presents a high intrinsic electrocatalytic activity for the reduction of triiodide ions. However, the photovoltaic performance of DSSCs with a MoN counter electrode is hindered by the large diffusion impedance of the MoN electrode. In response to this problem, a MoN–carbon nanotube (CNT) composite is prepared by nitridation of the precursor MoO2–CNTs, fabricated via a hydrothermal reaction of ammonium molybdate and carboxyl-functionalized CNTs. In the composite, MoN nanoparticles are well and stably dispersed on the surface of the CNTs, with a particle size of several tens of nanometers. Employing the composite as a counter electrode, the DSSC shows an energy conversion efficiency of 6.74%, which is much higher than that (5.57%) of the DSSC using pure MoN nanoparticles. The improvement is mainly attributed to a synergistic effect between the MoN nanoparticles and CNTs on ion diffusion and electrocatalysis. Electrochemical impedance spectra (EIS) indicate that the MoN–CNTs electrode has a lower ion diffusion impedance. It is believed that the smaller size of the MoN nanoparticles and the abundant porous structure in the MoN–CNTs composite are able to shorten the ion diffusion path and improve ion diffusion flux.

Reduced graphene oxide films fabricated by gel coating and their application as platinum-free counter electrodes of highly efficient iodide/triiodide dye-sensitized solar cells

This paper reports the preparation of reduced graphene oxide (rGO) films through the gel formation of rGO with liquid polyethylene glycol (PEG) of low molecular weight and the application of the rGO films as the platinum (Pt)-free counter electrode of highly efficient iodide/triiodide dye-sensitized solar cells (DSCs). rGO prepared through the reduction of graphene oxide can form physical gels with PEG by mechanical grinding. The rGO sheets form 3-dimensional solid networks in the gels. The rGO–PEG gels are processed into rGO films on substrates with good adhesion by doctor blade and subsequent removal of PEG through heating. The rGO films can effectively catalyze the electrochemical reduction of triiodide and are used as the counter electrode of iodide/triiodide DSCs. The optimal photovoltaic efficiency of DSCs with the rGO counter electrode is 7.19% under AM1.5G illumination (100 mW cm−2), which is only slightly lower than that (7.76%) of control DSCs with Pt prepared by pyrolysis as the counter electrode. This is the highest photovoltaic efficiency observed on the DSCs with iodide/triiodide as the redox couple and graphene as the counter electrode. The rGO films exhibit better stability in catalyzing the electrochemical reduction of triiodide and give rise to better aging stability of DSCs than Pt prepared by pyrolysis. The photovoltaic efficiency of DSCs is strongly dependent on the thickness of the rGO film, and the optimal rGO film thickness is 15 μm. The photovoltaic performance of DSCs is also affected by the method to prepare the rGO–PEG gels. The photovoltaic efficiency is only 6.15% or lower when the rGO–PEG gels are prepared by ultrasonication rather than mechanical grinding. This is attributed to the different morphologies of the rGO films achieved by different methods.

Hierarchically micro/nanostructured photoanode materials for dye-sensitized solar cells

As one of the most promising low cost alternatives to the traditional p–n junction photovoltaic device, the dye-sensitized solar cell (DSSC) has attracted immense attention from academic and industrial researchers in the last two decades. The size, structure and morphology of photoanode materials have been found to show significant influence on the photovoltaic performance of DSSCs. In this feature article, we briefly summarize the synthesis and properties of hierarchically micro/nanostructured semiconductor (TiO2, ZnO, SnO2) photoanode materials involving microspheres and one-dimensional nanostructure, and their photovoltaic performance in DSSCs.

Synthesis of hierarchical SnO2 octahedra with tailorable size and application in dye-sensitized solar cells with enhanced power conversion efficiency

Following the previous report on the fabrication of three-dimensional hierarchical SnO2 octahedra consisting of nanoparticles via a rapid sonochemical process (Wang et al., Chem.–Eur. J., 2010, 16, 8620–8625), the influences of ultrasonic time, amplitude, ratio of H2O–diethylene glycol (DEG), and different Sn salts on the morphology and size of SnO2 have been further investigated in the present article. The hierarchical SnO2 octahedra with average edge lengths of 0.5, 0.8, 1.0, 1.5 and 1.8 μm composed of 30–40 nm SnO2 nanoparticles have been successfully obtained. The power conversion efficiencies of dye-sensitized solar cells (DSSCs) based on the hierarchical SnO2 octahedra photoanodes varied from 5.57%, 5.82%, 6.40%, 6.45% to 6.80% with the corresponding octahedron sizes of 0.5, 0.8, 1.0, 1.5 and 1.8 μm, respectively. Intensity-modulated photocurrent spectroscopy (IMPS), intensity-modulated voltage spectroscopy (IMVS) and UV-vis diffuse spectroscopy were used to investigate the influences of the SnO2 octahedron size on the photovoltaic performances of DSSCs.

Aero-Sol-Gel Synthesis of Mesoporous TiO2 Nanoparticles and Their Photovoltaic Properties in Dye-Sensitized Solar Cells

ABSTRACTHighly mesoporous TiO2 nanoparticles (NPs) were synthesized by an aero-sol-gel process in this approach. By varying the mass fraction of inorganic templates, the formation of mesoporous TiO2 NPs with optimized surface area and pore volume distributions was examined. Then, the photovoltaic properties of the resulting mesoporous TiO2 NPs were systematically investigated by applying them into the photoanode of dye-sensitized solar cells (DSSCs). The mesoporous TiO2 NP-based DSSCs fabricated in this study showed an improved short circuit current density and power conversion efficiency compared with solid TiO2 NP-based DSSCs due to the increase of the amount of inorganic dye (N719) adsorption in the mesoporous TiO2 NPs. These mesoporous TiO2 NPs fabricated have a strong potential as an effective dye supporting and electron transfer medium to improve the photovoltaic performance of DSSCs.

A bilayer structure of a titania nanoparticle/highly-ordered nanotube array for low-temperature dye-sensitized solar cells

A chemical-free, environmentally friendly and harmless water immersion method is developed to delaminate anode oxidationtitania nanotube (TNT) arrays from Ti foils to obtain a free-standing TNT membrane. The as-synthesized TNT membrane with tunable thickness which is controlled by anodization time are used in low-temperature dye-sensitized solar cells (DSSCs) as a second layer to improve the DSSC efficiency. Compared with the common titania nanoparticle electrode, a water-delaminated TNT membrane electrode of 16 μm in thickness can significantly enhance the DSSCs photovoltaic performance with a short-circuit current density from 3.87 to 7.63 mA cm−2 and a fill factor from 0.637 to 0.708, which combinatorially lead to a remarkable increment of photo conversion efficiency from 1.70% to 3.68%. The results show that, owing to its vertically aligned ordered nanotube structure, the TNT arrays exhibit trifunctional behavior when used as an electrode, which are charge generation, light scattering and I3− diffusion improvement.

Facile synthesis of ZnO nanocrystals via a solid state reaction for high performance plastic dye-sensitized solar cells

We report the facile synthesis of ZnO nanocrystals via a one-step solid state reaction at room temperature and their application as the photoanode in plastic dye-sensitized solar cells (DSCs). ZnO nanoparticles were prepared utilizing zinc acetate dihydrate and sodium hydroxide with a short grinding time and without a sintering process. The as-prepared samples with the polycrystalline hexagonal wurtzite structure were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The obtained ZnO nanoparticles exhibited high crystallinity even without a high temperature sintering treatment during the preparation process. The effects of compression post-treatment on the photovoltaic performance of DSCs were also investigated using intensity modulated photocurrent spectroscopy (IMPS), incident photo-to-current conversion efficiency (IPCE), and electrochemical impedance spectroscopy (EIS). The results indicate that the improvement of power conversion efficiency after compression post-treatment of ZnO photoelectrode can be attributed to its high photoelectron collection efficiency and effective electron transport. Under the optimized conditions, a full plastic D149-sensitized ZnO solar cell measured under illumination of 100 mW·cm−2 (AM 1.5G) presents an energy conversion efficiency of 3.76% with open-circuit voltage of 0.688 V, short-circuit current density of 8.55 mA·cm−2, and fill factor of 0.64. These results demonstrate that the one-step solid state reaction is a convenient and effective method for the synthesis of ZnO nanocrystals for use in plastic DSCs. Open image in new window

Phenoxazine-Based Dyes with Dual Electron Donating Moiety for Organic Dye-Sensitized Solar Cells

Highly effective phenoxazine (POZ)–based dyes (dye1, dye2, dye3, dye4 and dye5) for dye-sensitized solar cells (DSSCs) were designed and studied theoretically by using density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. When the electronic properties of dye2 were further analyzed in terms of the coupling among its moieties, it was found that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the dye2 was originated from the HOMO of the POZ and the triphenylamine moieties and the LUMO of the cyanoacrylic acid moiety, respectively. It was found that HOMO = >LUMO (and HOMO-1 = >LUMO) transition could be considered as an intramolecular charge-transfer (ICT) transition and HOMO = >LUMO+1 transition, however, as the mixture of ICT and π–π* excitation. It was shown that through the additional electron donating group, absorption bands due to HOMO = >LUMO transition were red-shifted and another strong absorption bands appeared as peaks between 400 and 450 nm. Of the POZ-based dyes, we showed that dye5 would have the best photovoltaic properties in terms of light-harvesting efficiency and energy-antenna consideration. These results suggested organic dye sensitizers with dual electron donating group would give good photovoltaic performance for DSSCs.

Syntheses and characterization of several nickel bis(dithiolene) complexes with strong and broad Near-IR absorption

Several nickel bis(dithiolene) complexes with strong and broad absorptions in the Near-IR (NIR) region (700–1100nm) were synthesized by using green and simple synthetic routes. The physical and chemical properties of these dyes were systematically studied, including structure, optical spectroscopy and electrochemical behavior, etc. These NIR dyes were first applied to dye-sensitized solar cells (DSCs) and the photoelectrochemical performances were also investigated. The effects of different substituent groups on the properties of the dyes and photovoltaic performances of DSCs were discussed. Furthermore, we also applied the synthesized NIR dyes for constructing NIR absorbing filter. With their particular photoelectrochemical properties, the nickel bis(dithiolene) complexes exhibit promising prospects for future application.

Effect of polyethyleneimine on the growth of ZnO nanorod arrays and their application in dye-sensitized solar cells

A series of oriented hexagonal wurtzite ZnO nanorod-array films were grown on fluorine-doped tin oxide (FTO) coated glass substrates by chemical process. The effect of polyethyleneimine (PEI) on the structure and micro-morphology of ZnO nanorod array films, as well as the photoelectric conversion properties in dye-sensitized solar cells (DSSCs) was analyzed. It was found that with the addition of PEI in growth solution, the ZnO nanorods became smaller in diameter and longer in length and hence the dye absorption and the photovoltaic performance of DSSCs were improved. A power conversion efficiency of 2.30% had been achieved on a DSSC based on a 7.9 μm-long nanorod array film prepared by a growth solution containing the PEI.