Non-aqueous preparation of anatase TiO2 hollow microspheres for efficient dye-sensitized solar cells

TiO₂ hollow spheres are fabricated by a facile and template-free approach, which is efficient, cost-saving and favorable for large scale production. The as-prepared TiO₂ hollow spheres with diameters ranging from 1 to 1.5 μm and a shell thickness of 150 nm are formed by the self-assembly of nanoparticles with a size of about 12 nm. The mesoporous TiO₂ hollow spheres possess a high specific surface area up to 166.2 m² g⁻¹. TiO₂ hollow spheres show superior light trapping characteristics and significantly improve the light scattering ability. The formation of hollow structure is interpreted by the Ostwald ripening mechanism. By employing a double-layered photoanode made of the as-prepared TiO₂ hollow spheres as the overlayer and P25 as the bottom layer, the dye-sensitized solar cell achieved a power conversion efficiency of 7.90%, which is ascribed to the enhanced dye loading and light scattering ability of TiO₂ hollow spheres.     

Synthesis and characterization of anatase TiO2 nanotubes and their use in dye-sensitized solar cells

Anatase TiO₂ nanotubes (NTs) with the diameter of about 12 nm and the length of several hundreds nanometers were synthesized by hydrothermal method. The samples were characterized by X-ray diffraction (XRD), transmitting electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmet–Teller (BET) measurements. The NTs are used to make composites photoanode with pristine TiO₂ nanoparticles in dye-sensitized solar cells (DSSCs). It was found that the NT/nanoparticle ratio had a pronounced impact on the performance of solar cells. The electrode composite has better photoelectric properties than the full nanoparticle and NTs solar cells. The optimum content NTs, was found to be 5%, at which content the incident photon to current efficiency was about 63.1%, an 13.8% increment compared to that using full P25 under the same condition.     

TiO2 coated urchin-like SnO2 microspheres for efficient dye-sensitized solar cells

Urchin-like SnO2 microspheres have been grown for use as photoanodes in dye-sensitized solar cells （DSSCs）. We observed that a thin layer coating of TiO2 on urchin-like SnO2 microsphere photoanodes greatly enhanced dye loading capability and light scattering ability, and achieved comparable solar cell per- formance even at half the thickness of a typical nanocrystalline TiO2 photoanode. In addition, this photoanode only required attaching -55% of the amount of dye for efficient light harvesting compared to one based on nanocrystalline TiO2. Longer decay of transient photovoltage and higher charge recombination resistance evidenced from electrochemical impedance spectroscopy of the devices based on TiO2 coated urchin-like SnO2 revealed slower recombination rates of electrons as a result of the thin blocking layer of TiO2 coated on urchin- like SnO2. TiO2 coated urchin-like SnO2 showed the highest value （76.1 ms） of electron lifetime （＇r） compared to 2.4 ms for bare urchin-like SnO2 and 14.9 ms for nanocrystalline TiO2. TiO2 coated SnO2 showed greatly enhanced open circuit voltage （Voc）, short-circuit current density （Jsc） and fill factor （FF） leading to a four-fold increase in efficiency increase compared to bare SnO2. Although TiO2 coated urchin-like SnO2 showed slightly lower cell efficiency than nanocrystalline TiO2, it only used a half thickness of photoanode and saved -45% of the amount of dye for efficient light harvesting compared to normal nanocrystalline TiO2.     

Microwave-assisted hydrothermal synthesis and characterization of TiO2 microspheres for efficient dye-sensitized solar cells

Journal of Materials Science: Materials in Electronics - Mesoporous TiO2 microspheres (MS) have been synthesized by a microwave-assisted hydrothermal technique. The samples were analyzed by XRD...     

Synthesis of mesoporous anatase TiO2 nanotubes by a hydrothermal treatment and their use in solid-state dye-sensitized solar cells

Mesoporous anatase TiO2 nanotubes (NTs) with the diameter of about 7 12 nm and the length of several hundred nanometers were synthesized by a hydrothermal method on commercial TiO2 particles in NaOH followed by HCI washing. The samples were characterized by X-ray diffraction (XRD), transmitting electron microscopy (TEM), and Brunauer-Emmet-Teller (BET) measurements. The hydrothermal treatment temperature at 130 degrees C was shown to affect not only the extent of particle-to-sheet conversion, and thus the resulting structures of the NTs, but also the anatase-to-rutile transformation. The surface area of the NTs was 200 m2g(-1). This value was much higher in comparison to TiO2 nanoparticles of 50 m2g(-1). It was also found that the NT photoelectrodes had a pronounced impact on the performance of solar cells as compared to nanoparticle ones. This was probably due to lead to a significantly higher specific dye loading and, for certain hydrothermal treatments, resulting in a doubling of the solar cell efficiency (in our case from 2.84% to 4.03% of AM 1.5 conditions).     

Synthesis and dye-sensitized solar cell performance of nanorods/nanoparticles TiO2 from high surface area nanosheet TiO2

High surface area nanosheet TiO2 with mesoporous structure were synthesized by hydrothermal method at 130 degrees C for 12 h. The samples characterized by XRD, SEM, TEM, SAED, and BET surface area. The nanosheet structure was slightly curved and approximately 50-100 nm in width and several nanometers in thickness. The as-synthesized nanosheet TiO2 had average pore diameter about 3-4 nm. The BET surface area and pore volume of the sample were about 642 m(2)/g and 0.774 cm(3)/g, respectively. The nanosheet structure after calcinations were changed into nanorods/nanoparticles composite with anatase TiO2 structure at 300-500 degrees C (10-15 nm in rods diameter and about 5-10 nm in particles diameter). The solar energy conversion efficiency (eta) of the cell using nanorods/nanoparticles TiO2 (from the nanosheet calcined at 450 degrees C for 2 h) with mesoporous structure was about 7.08% with Jsc of 16.35 mA/cm(2), Voc of 0.703 V and ff of 0.627; while eta of the cell using P-25 reached 5.82% with Jsc of 12.74 mA/cm(2), Voc of 0.704 V, and ff of 0.649.     

介孔TiO2微球水热法合成及在染料敏化太阳能电池中的应用

以Ti(SO4)2为钛源,采用尿素辅助水热法合成了介孔TiO2微球,利用XRD、FESEM和比表面积分析仪对样品的晶型、形貌和比表面积进行分析,探讨了尿素加入量对TiO2微球的颗粒尺寸、比表面积、孔径和孔容的影响。采用刮涂法,用所合成的介孔TiO2微球制备了染料敏化太阳能电池(DSSC)的光阳极,结果表明,尿素用量为1.2g合成的介孔TiO2微球所组装的电池在模拟太阳光的照射下(100mW/cm2,AM1.5),光电转换效率为6.2%,明显高于商用P25纳晶所组装的电池光电转换效率(4.24%)。     

Effects of TiO2 structures in dye-sensitized solar cell

In this work, the effects of crystalline structure of the TiO2, which is incorporated in fabrication of the n-type electrode, on the DSSC performance were investigated in terms of the energy conversion efficiency. In this effort, TiO2 nanoparticle pastes with varying contents of rutile and anatase structures were prepared by using the ethanol mixing method. The most efficient photo-electro-chemical performance was achieved for the DSSC fabricated with the TiO2 paste in which the anatase form of the nanocrystal extends to 90%.     

Controlled fabrication of TiO2 rutile nanorod/anatase nanoparticle composite photoanodes for dye-sensitized solar cell application

We present a straightforward procedure to prepare composite photoanodes which consisted of TiO2 rutile nanorods/anatase nanoparticles synthesized under hydrothermal conditions, with the ratio of rutile to anatase controlled simply by adjusting the volume of nitric acid. The as-prepared TiO2 composites exhibited high specific surface area, light-scattering effect, and good crystallinity. The dye-sensitized solar cells (DSCs) using the TiO2 composites showed higher short-circuit photocurrent and overall conversion efficiency than the DSC from pure-anatase nanoparticles. The highest conversion efficiency was achieved from the DSC based on TiO2 nanocomposites with 24 wt% rutile nanorods, which was attributed to improved light harvesting caused by the enhancement of specific surface area and scattering effect from rutile nanorods.     

高分子在染料敏化纳晶TiO2太阳电池中的应用研究

染料敏化纳晶TiO2太阳电池是一种极具竞争力的新型太阳能电池,它主要由三部分组成:染料敏化的TiO2纳晶电极、电解质及对电极,每一组成部分又由几种材料组成,每一种材料都在电池将太阳能转化为电能的过程中发挥特定的作用.为了进一步降低成本、改善性能,用高分子材料代替其中的一种或几种组成材料成为目前研究的一个热点,本文论述了高分子材料在染料敏化纳晶TiO2太阳电池中的应用研究进展,对出现的问题进行分析讨论.     

Influence of TiO2 nanofiber additives for high efficient dye-sensitized solar cells

TiO2 nanofibers were prepared from a mixture of titanium-tetra-isopropoxide and poly vinyl pyrrolidone by applying the electrospinning method. The samples were characterized by XRD, FE-SEM, TEM and BET analyses. The diameter of electrospun TiO2 nanofibers is in the range of 70 approximately 160 nm. To improve the short-circuit photocurrent, we added the TiO2 nanofibers in the TiO2 electrode of dye-sensitized solar cells (DSSCs). TiO2 nanofibers added in DSSCs can make up to 20% more conversion energy than the conventional DSSC with only TiO2 films only.     

Rutile TiO2 microspheres with exposed nano-acicular single crystals for dye-sensitized solar cells

Uniquely structured rutile TiO₂ microspheres with exposed nano-acicular single crystals have been successfully synthesized via a facile hydrothermal method. After calcination at 450 °C for 2 h, the rutile TiO₂ microspheres with a high surface area of 132 m²/g have been utilized as a light harvesting enhancement material for dye-sensitized solar cells (DSSCs). The resultant DSSCs exhibit an overall light conversion efficiency of 8.41% for TiO₂ photoanodes made of rutile TiO₂ microspheres and anatase TiO₂ nanoparticles (mass ratio of 1:1), significantly higher than that of pure anatase TiO₂ nanoparticle photoanodes of similar thickness (6.74%). Such a significant improvement in performance can be attributed to the enhanced light harvesting capability and synergetic electron transfer effect. This is because the photoanodes made of rutile TiO₂ microsphere possess high refractive index which improves the light utilisation efficiency, suitable microsphere core sizes (450–800 nm) to effectively scatter visible light, high surface area for dye loading, and synergetic electron transfer effects between nanoparticulate anatase and nano-acicular rutile single crystals phases giving high electron collection efficiency.      

Highly efficient fibrous dye-sensitized solar cells based on TiO2 nanotube arrays

The structure of fibrous dye-sensitized solar cells, which were constructed by a TiO(2) nanotube array on Ti wire as the photoanode twisted by a Pt wire counter electrode, has been first systematically investigated by accurately controlling the thread pitch distance of screwed Pt wire. It has been revealed that the thread pitch will strongly influence the photovoltaic performance and kinetic processes in fibrous solar cells. The effect of the length of the TiO(2) nanotube on cell performance has also been discussed. After optimization, a relatively universal optimized thread pitch value of 1 mm for fibrous DSCs has been proved and the light-to-electricity conversion efficiency has been remarkably improved to 5.84%.     

TiO2纳米管阵列电极染料敏化太阳能电池

采用电化学阳极氧化法在纯钛片表面制备了高度有序的TiO2纳米管阵列。利用SEM、XRD分别对TiO2纳米管阵列的形貌、晶型进行了表征,并通过线性扫描伏安法对N719染料敏化纳米管阵列电极的光电性能进行了研究。实验结果表明,纳米管阵列的管径和长度随着阳极氧化电压的升高和氧化时间的延长都分别相应增加。同时还发现,通过450℃热处理的TiO2纳米管阵列,具有较好的锐钛矿晶型结构,其光电转化效率为2.1%。     

Template-free synthesis of hierarchical TiO2 structures and their application in dye-sensitized solar cells

We demonstrate here the synthesis of a hierarchical TiO(2) architecture without any surfactants or templates. Two kinds of structure existed simultaneously, the ordered nanoarrays at bottom provided direct conduction pathway for photo generated electrons, while the upper micro-flowers consisted of nanobelt as building units increased the light harvesting ability as the scattering part. The formation mechanism of the hierarchical architecture has been proposed by studying the morphology evolution processes upon reaction time. The performance of dye-sensitized solar cells based on the obtained hierarchical anatase TiO(2) has been also studied, giving a J(SC) = 12.44 mA cm(-2), V(OC) = 0.64 V, FF = 69.05%, and η = 5.53%, which is superior than commercial TiO(2) (P25). The UV-vis results prove that the obtained morphology is beneficial to light-scattering and thus increases the light harvesting ability. This hierarchical TiO(2) structure offers great potential for the development of high-efficiency DSSCs.     

Growth of TiO2 nanowire bundle arrays and their application in dye-sensitized solar cells

Highly oriented single-crystalline TiO₂ nanowire bundle arrays on transparent conductive fluorine-doped tin oxide substrates are prepared by hydrothermal method using the precursors of titanium butoxide, deionized water and hydrochloric acid. The structure and morphology characteristics of all the samples have been analyzed by X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy. Results show that the diameter, length, and density of the nanowire bundle arrays can be varied by changing the growth parameters, such as growth time, initial reactant concentration and acidity. The enhanced (002) peak in XRD patterns indicate that the nanowire is well crystallized and grow perpendicular to the substrate. The high resolution transmission electron microscope images and selected-area electron diffraction patterns confirm that there are approximately 10–30 nanowires in each bundle. The nanowire is single crystalline. Dye-sensitized solar cells assembled from oriented TiO₂ nanowire bundle arrays as the photoanode are studied. The light-to-electricity conversion efficiency is about 2.17 %.     

Organized mesoporous TiO2 films exhibiting greatly enhanced performance in dye-sensitized solar cells

The Pluronic P123 templated mesoporous TiO2 film was grown via layer-by-layer deposition and characterized by a novel methodology based on the adsorption of n-pentane. Multiple-layer depositions did not perturb the mesoporous structure significantly. Our TiO2 film was sensitized by a newly developed Ru-bipyridine dye (N945) and was applied as a photoanode in dye-sensitized solar cell. The 1-microm-thick mesoporous film, made by the superposition of three layers, showed enhanced solar conversion efficiency by about 50% compared to that of traditional films of the same thickness made from randomly oriented anatase nanocrystals.     

The use of ZrO2 mixed TiO2 nanostructures as efficient dye-sensitized solar cells' electrodes

The mixed oxide of zirconium (ZrO₂) and titanium (TiO₂) nanostructures have been synthesized and used as electrodes for dye-sensitized solar cells (DSC). The TiO₂–ZrO₂ mixed oxide powder has a larger surface area than the pure component of TiO₂. For the UV action spectra of unsensitized photochemical cell, the TiO₂–ZrO₂ mixed oxide electrode band gap (E_g) around 3.27 eV, which is higher than that of pure component of titania (E_g = 3.2 eV). The increases in both of BET surface area and band gap contributed to the improvement on short-circuit photocurrent and open-circuit voltage, respectively. The DSC fabricated by TiO₂–ZrO₂ mixed oxide electrode significantly improved solar energy conversion efficiency when compared to a cell that was fabricated only by pure component of TiO₂.