染料敏化太阳能电池的非金属有机敏化剂

染料敏化太阳能电池(DSSC)是一种新型的太阳能电池,综述了DSSC的非金属有机染料敏化剂的研究现状,分析了各类敏化剂的结构与电池的能量转换效率的关系,并提出非金属有机染料结构的设计思路。     

Electron transfer properties of organic dye-sensitized solar cells based on indoline sensitizers with ZnO nanoparticles

Two indoline dyes, coded D149 and D205, were used as the sensitizers of ZnO dye-sensitized solar cells (DSCs) with optimal energy conversion efficiencies of more than 5%, under AM 1.5 full sunlight illumination (100?mW?cm( - 2)). Higher interfacial charge transfer rate and retardant fluorescence decay confirmed from transient fluorescence illustrated that D205-sensitized ZnO DSCs could possess better electron transport than D149-sensitized ZnO DSCs. The enhancement of V(oc) and J(sc) for D205-sensitized ZnO DSCs was ascribed to the effective suppression of electron recombination by extending the alkyl chain on the terminal rhodanine moiety from ethyl to octyl. The evidence of enhanced electron diffusion coefficient was further shown by electrochemical impedance spectroscopy (EIS).     

TiO2介孔薄膜电阻对染料敏化太阳能电池光电转换性能的影响

TiO2介孔薄膜的电阻可能是影响染料敏化太阳能电池光电转化效率的主要因素之一.设计了一种可用于测试TiO2介孔薄膜电阻的方法,研究了2种不同电阻值的TiO2介孔薄膜的电阻变化规律和2种TiO2介孔薄膜组装的染料敏化太阳能电池(DSC)的光电转换性能.结果显示,采用低电阻的TiO2薄膜光电极有利于DSC光电转换效率的提高.     

Organic photosensitizers with a heteroleptic dual donor for dye-sensitized solar cells

Using DFT and TDDFT calculations, we investigated the substitution effect in the electronic and optical properties of dye sensitizers with a dual donor composed of triphenylamine and/or indoline moieties. Due to replacement with the dual donor moieties, the HOMO levels were split into HOMO and HOMO - 1 levels, and the bandgaps between the HOMO and LUMO levels decreased, leading to the creation of bathochromically extended absorption spectra. Nearly degenerated splitting of the HOMO levels resulted from the similarity of the electronic structure between the HOMO and the HOMO - 1 levels, delocalized over both dual-donor moieties, when replacing the dual donors. It was shown that the additional electron-donating group creates an additional absorption band and causes a cascading two-electron process aiding the charge separation process. Owing to a more panchromatic attribute, easier energy transfer and feasible retardation of the recombination between the injected electrons and the electrolyte, it is expected that dyeTI will show better performance than the other dyes (dyeT dyeTT and dyeIT) as denoted here in terms of the conversion efficiency of dye-sensitized solar cells (DSSCs). This work presents the probable benefits of dye sensitizers with dual-donor moieties and provides insight into the development of more efficient dye sensitizers for DSSCs through modification of the Frontier molecular orbitals.     

Influence of defect density on the ZnO nanostructures of dye-sensitized solar cells

The relationship between bilayer nanostructure,defect density and dye-sensitized solar cell (DSCC) performances was investigated. By adjusting bilayer nanostructures,defect density of ZnO nanodendrite-nanorods structure was decreased comparing to that of nanoflowernanorods structure. The performances of DSCC based on ZnO nanodendrites-nanorods structure and nanoflowernanorods structure were studied by Raman spectrum, room
temperature photoluminescence, dye loading, photocurrent density-voltage characteristic and open-circuit voltage decay (OCVD) technique. The device with nanodendritenanorods structure has lower charge recombination rate and prolonged electron lifetime due to its microstructure feature.     

Nanowire dye-sensitized solar cells

Excitonic solar cells-including organic, hybrid organic-inorganic and dye-sensitized cells (DSCs)-are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient and stable excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fifth as large as a nanoparticle cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.     

碘盐对聚合物凝胶电解质及染料敏化太阳电池性能的影响

通过简单方法合成了一种新型有机碘盐N-甲基吡啶碘，以苯乙烯-丙烯腈共聚物（AS树脂）为聚合物凝胶电解质基体，丙烯碳酸酯及乙烯碳酸酯双组分有机溶剂为液相，制备了含有机碘盐（N-甲基吡啶碘）和无机碘盐（NaI）的AS树脂基聚合物凝胶电解质，比较了两种碘盐对聚合物凝胶电解质导电性能及染料敏化纳米晶太阳电池光电性能的影响，发现含有机碘盐的聚合物凝胶电解质具有较高的电导率，所制备的DSSC光电性能也较好。     

Theoretical study of YD2-o-C8-based derivatives as promising sensitizers for dye-sensitized solar cells

To screen efficient sensitizers for dye-sensitized solar cells (DSSCs), two series of porphyrin sensitizers have been reengineered based on one of the best sensitizers YD2-o-C8 by introducing different heterocycles into acceptor part to form stronger acceptors. The electronic structures and optical properties of these sensitizers have been investigated using density functional theory and its time-dependent density functional theory version. The computational results suggest that the stronger acceptor can result in a narrower HOMO–LUMO energy gap, an obvious red-shift and stronger absorption in long-wavelength region compared with YD2-o-C8. Meanwhile, the analyses of electron density difference plots suggest that all designed sensitizers possess longer electron transfer distance, larger fraction of electron exchange, and smaller overlap between the zones of density depletion and increment than these of YD2-o-C8, indicating enhanced electron transfer ability from donor to acceptor groups. Moreover, the designed dyes exhibit good performance in terms of the electron injection ability, the excited state lifetime, and the strength of the interaction between dye and the TiO₂ surface. As a whole, all the designed dyes, especially P4 and P6 may act as excellent sensitizers for high-efficiency DSSCs.     

阻挡层薄膜对染料敏化太阳能电池光电性能的影响

采用溶胶-凝胶法制备了不同浓度的TiO2溶胶,通过旋转涂覆法在光阳极导电玻璃基底上制备了阻挡层薄膜,以此来阻止导电玻璃基底上光生电子与电解液中I-3的复合,提高了染料敏化太阳能电池(DSSC,dye-sensitized solar cells)的光电转换效率.研究了不同TiO2溶胶浓度及阻挡层厚度对DSSC光电性能的影响.结果表明,由于阻挡层的引入有效地提高了DSSC的光电性能,最高光电转换效率达到了5.30%,比无阻挡层的DSSC的光电转换效率提高了大约27%.     

Influence of the sensitizer adsorption mode on the open-circuit potential of dye-sensitized solar cells

We report a combined experimental and theoretical study on the origin of the different open circuit potentials observed in dye-sensitized solar cells using Ru(II)-polypyridyl homoleptic and heteroleptic sensitizers. We have measured the photovoltaic data of different sensitizers and used DFT calculations to analyze the electronic structure of dye-sensitized TiO(2) nanoparticles. Heteroleptic sensitizers adsorb onto TiO(2) via a single bipyridine, leading to a TiO(2) conduction band downshift and overall reduction of the cell open circuit potential.     

Novel heteroleptic ruthenium (II) complex with DPBPZ derivative for dye-sensitized solar cells

Herein, as Ru(II) complex for the dye-sensitized solar cells (DSSCs), we designed and investigated a novel heteroleptic ruthenium complex [Ru(dcbpy)(dpbpz)(NCS)2] with dpbpz derivative to enhance photovoltaic performance. The density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were used to gain insight into the factors responsible for photovoltaic properties as dye sensitizer. Molecular orbitals analysis confirmed that HOMO of [Ru(dcbpy)2(NCS)2] and [Ru(dcbpy)(dpbpz)(NCS)2] are delocalized over the ruthenium t2g character with sizable contribution from the NCS ligand orbitals. The LUMO of [Ru(dcbpy)2(NCS)2] is localized over the dcbpy moiety. However, LUMO of [Ru(dcbpy)(dpbpz)(NCS)2] is localized over the dpbpz moiety and LUMO + 1 is localized the dcbpy moiety. Overall, the absorption spectrum of the present Ru complex was more broad than that of [Ru(dcbpy)2(NCS)2] known as N3 dye. Especially, absorption band in the region between 500 nm and 600 nm was red-shifted. Moreover, the distance between the HOMO of [Ru(dcbpy)(dpbpz)(NCS)2] and the anchoring moiety is longer than that of [Ru(dcbpy)2(NCS)2]. This means that [Ru(dcbpy)(dpbpz)(NCS)2] have longer charge-separated lifetime than [Ru(dcbpy)2(NCS)2. These results are attributed to the extended pi-conjugation of dpbpz moiety. Therefore, we suggest that newly designed [Ru(dcbpy)(dpbpz)(NCS)2] heteroleptic ruthenium complex would be a good candidate as a dye sensitizer of DSSCs, comparable to [Ru(dcbpy)2(NCS)2].     

Novel DCM-based organic dye with a heteroleptic dual-electron donor for dye-sensitized solar cells

A new DCM-based organic dye with a heteroleptic dual electron donor was designed and its electronic and optical properties were investigated theoretically for dye-sensitized solar cells (DSSCs). In this study, heteroleptic Dab dye was compared with other homoleptic dyes (Daa and Dbb). To gain insight into the factors responsible for photovoltaic efficiency, density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations of these dyes were conducted. It showed that Dab dye is available as a photovoltaic device from the energy diagram for the TiO2 electrode and the iodide electrolyte. It also showed that although Dab dye produces slightly stronger absorption at above 600 nm, Dbb dye would show a better overall absorption property. Owing to the strong electron density and high proximity of its anchoring carboxylic group to LUMO + 1 and LUMO, however, it is expected that Dab dye with a heteroleptic dual donor will show a competitive performance compared to other dyes with homoleptic dual donors in the conversion efficiency for DSSCs.     

Improving conversion efficiency of dye-sensitized solar cells by metal plasma ion implantation of ruthenium ions

Dye-sensitized solar cells (DSSC) are based on the concept of photosensitization of wide-band-gap mesoporous oxide semiconductors. At present, DSSC have ventured into advanced development and pilot production. Our current research emphasizes on improvements on titanium dioxide (TiO₂) photosensitivity under visible light irradiation by using metal plasma ion implantation (MPII). The anatase TiO₂ electrode was prepared via a sol-gel process and deposited onto indium-tin oxide glass substrates. Subsequently, the as-deposited TiO₂ films were subjected to MPII at 20 keV in order to incorporate ruthenium (Ru) atoms onto the TiO₂ surface layer. The Ru-implanted TiO₂ thin film possessed nanocrystalline Ru clusters of 20 nm in diameter and distributed in near surface layer of TiO₂ films. The Ru clusters showed effective in both prohibiting electron-hole recombination and generating additional Ru-O impurity levels for the TiO₂ band gap structure. A significant reduction of TiO₂ band gap energy from 3.22 to 3.11 eV was achieved, which resulted in the extension of photocatalysis of TiO₂ from UV to Vis regime. A small drop of photoelectric performance of 8% was obtained due to the incorporation of Ru atoms in the surface layer of TiO₂, a similar side effect as observed in the Fe-implanted TiO₂. However, the overall retention of the photocatalysis capability is as high as 92% when switch from UV to Vis irradiation. The improvement of the photosensitivity of TiO₂ DSSC by means of metal plasma ion implantation is promising.     

染料敏化太阳能电池中电解质的研究进展

电解质是染料敏化太阳能电池的一个重要组成部分,是影响电池光电性能和稳定性的重要因素.电解质根据物理状态不同将其分为液体电解质、准固态电解质和固态电解质.介绍了这三种不同电解质的性能、各自的优点及存在问题,并对染料敏化太阳能电池中电解质在国内外研究发展现状进行了综述.     

The effect of growth conditions on the properties of ZnO nanorod dye-sensitized solar cells

In this article, we report ZnO nanorod samples grown on transparent conductive SnO₂:F (FTO) glass substrates by two different growth routes through hydrothermal method in a closed autoclave. One route is one-step continuous growth for 10 h. The other route is discrete multi-step growth for total 48 h. In this process, fresh solution was repeatedly introduced in every step. The structural, photoluminescence (PL) and photovoltaic properties of the as-prepared nanorod arrays were investigated. The nanorod arrays obtained through multi-step growth show longer rods, higher aspect ratio, larger spacing, better crystalline quality. The PL spectrum of nanorod arrays obtained through multi-step growth shows a strong and sharp near-band-gap emission (UV) peak and a weak green-yellow emission (GY) peak (I_UV/I_GY = 7.7), which also implies its good crystallinity and high optical quality. Dye-sensitized solar cells based on ZnO nanorod arrays were fabricated, and those grown with discrete multi-step procedure present better photovoltaic properties duo to its special morphology and better crystal quality.     

Influence of annealing temperature on performance of dye-sensitized TiO2 nanorod solar cells

Single-crystal rutile TiO₂ nanorod (NR) arrays have been synthesized on the fluorine-doped tin oxide substrates, followed by an annealing at 200–600?°C. It is found that DSSCs fabricated using TiO₂ NR arrays which undergo annealing display an increased efficiency than those that do not undergo annealing. The optimal efficiency of 4.42% power conversion is achieved in the DSSC made with 500?°C annealed arrays, which show a 450% increase in the overall conversion efficiency. The improvement is ascribed to the increased light harvesting, the enhanced electric contact and the suppressed recombination of the injected electrons with redox species in the electrolyte.     

Influence of donor substitution at $$\mathrm{D}{-}\uppi {-}\mathrm{A}$$ architecture in efficient sensitizers for dye-sensitized solar cells: first-principle study

Using density functional theory and time-dependent density functional theory, we theoretically studied a new series of five novel metal-free organic dyes, namely D1–D5, for application in dye-sensitized solar cells based on donor–\(\uppi \)-spacer–acceptor (\(\mathrm{D}{-}\uppi {-}\mathrm{A}\)) groups. In this present study, five different donor groups have been designed based on triphenylamine–stilbene–cyanoacrylic acid (TPA–St–CA). The electronic structures, UV–visible absorption spectra and photovoltaic properties of these dyes were investigated. Different exchange-correlation functionals were used to establish a proper methodology procedure for calculation and comparison to experimental results of dye TPA–St–CA. The TD-WB97XD method, which gives the best correspondence to experimental values, is discussed. The calculated results reveal that the donor groups in D2 and D3 are promising functional groups for \(\mathrm{D}{-}\uppi {-}\mathrm{A}\). In particular, the D2 dye showed small energy levels and red-shift, negative \(\Delta {G}_{\mathrm{inject}}\), fastest regeneration and largest dipole moment and exciton binding energy when compared with TPA–St–CA.     

Influence of niobium doping in hierarchically organized titania nanostructure on performance of dye-sensitized solar cells

Niobium doped hierarchically organized TiO2 nanostructures composed of 20 nm size anatase nanocrystals were synthesized using pulsed laser deposition (PLD). The Nb doping concentration could be facilely controlled by adjusting the concentration of Nb in target materials. We could investigate the influence of Nb doping in the TiO2 photoelectrode on the cell performance of dye-sensitized solar cells (DSSCs) by the exclusion of morphological effects using the prepared Nb-doped TiO2 anostructures. We found no significant change in short circuit current density (Jsc) as a function of Nb doping concentration. However, open circuit voltage (Voc) and fill factor (FF) monotonously decrease with increasing Nb concentration. Dark current characteristics of the DSSCs reveal that the decrease in Voc and FF is attributed to the decrease in shunt resistance due to the increase in conductivity TiO2 by Nb doping. However, electrochemical impedance spectra (EIS) analysis at open circuit condition under illumination showed that the resistance at the TiO2/dye/electrolyte interface increases with Nb concentration, revealing that Nb doping suppress the charge recombination at the interface. In addition, electron life time obtained using characteristic frequency in Bode plot increases from 14 msec to 56 msec with increasing Nb concentration from 0 to 1.2 at%. This implies that the improved light harvesting can be achieved by increasing diffusion length through Nb-doping in the conventional TiO2 photoelectrode.     

Callindra haematocephata and Peltophorum pterocarpum flowers as natural sensitizers for TiO2 thin film based dye-sensitized solar cells

We have studied the performance of dye-sensitized solar cells employing natural dye extracted from the flowers Callindra haematocephata and Peltophorum pterocarpum as sensitizers for TiO₂ photoanode. The extracts have shown appreciable absorption in the visible region. FTIR studies indicated the presence of anthocyanins and β-carotene in the flowers of C. haematocephata and P. pterocarpum respectively. The extracts were anchored on TiO₂ film deposited on transparent conductive glass (FTO) which were used as photoanode. The dye coated TiO₂ film electrode, Pt counter electrode and electrolyte (I⁻₃) assembled into a cell module was illuminated by a light source with intensity 100 mW/cm² to measure the photoelectric conversion efficiency of the DSSCs. From the J-V characteristic curves of cells, the parameters related to the solar cell performance were determined. The conversion efficiency of the DSSC employing natural dye extract from the flower C. haematocephata and P. pterocarpumwere was found as 0.06% and 0.04%, with open-circuit voltage (V_OC) of 370 mV & 400 mV, short-circuit current density (J_SC) of 0.25 mA/cm² & 0.15 mA/cm², fill factor (FF) of 0.70 & 0.71 and P_max of 65 & 45 μW cm⁻² respectively. The extract of the flower C. haematocephata exhibited better photosensitization action compared to the flower of P. pterocarpum.     

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.