Efficient eosin y dye-sensitized solar cell containing Br-/Br3- electrolyte

We found that Br-/Br3- is more suitable than an I-/I3- couple in dye-sensitized solar cells in terms of higher open-circuit photovoltage (Voc) production and higher overall energy conversion efficiency (eta) if the dye sensitizer has a more positive potential than that of Br-/Br3-. Under simulated AM1.5 one sun, an eosin Y dye-sensitized solar cell containing 0.4 M LiBr + 0.04 M Br2 electrolyte in acetonitrile yielded a short-circuit photocurrent (Jsc) of 4.63 mA cm(-2), Voc of 0.813 V, and fill factor (FF) of 0.693, corresponding to 2.61% of eta. Under the same conditions except for the electrolyte 0.4 M LiI + 0.04 M I2 in acetonitrile instead, the device produced 1.67% of eta (Jsc = 5.15 mA cm(-2), Voc = 0.451 V, FF = 0.721). Replacement of I-/I3- with Br-/Br3- in eosin Y dye-sensitized solar cells yielded a significant increase in Voc offset by slight decreases in Jsc and FF, leading to an increase in eta by 56%. The significant gain in Voc was attributed to the enlarged energy level difference between the redox potential of the electrolyte and the Fermi level of TiO2 and the suppressed charge recombination as well. The rate for charge recombination between bromine and the injected electrons was determined to be first order in bromine.     

Composite Electrode SnO2／TiO2 for Dye-Sensitized Solar Cells

Composite nanoporous electrode SnO2/TiO2 was fabricated for the dye sensitized solar cell (DSSC) with N3 (Cis-Ru). After introducing of TiO2, the open-circuit photovoltage (Voc) was higher than that of the pure SnO2 electrode, while short-circuit photocurrent (Isc) was varied with the ratio of the TiO2. Appropriate content of the TiO2 can be beneficial to the efficiency of the solar cell, and it gives negative impact on the composite electrode when the content of TiO2 is higher.     

Role of nanochemical environments in porous TiO2 in photocurrent efficiency and degradation in dye sensitized solar cells

Elongated dye sensitized solar cells with a thickness gradient of the nanoporous TiO2 front electrode were used to assess the impact of the layer thickness on photocurrent and degradation. The photocurrent efficiency passes through a maximum (in our case at about 12 microm). Interestingly, the degradation rate also strongly depends on the layer thickness and is about 3 times faster for a 15-microm cell (in comparison with a 1-microm cell). To explain these nonanticipated results, a model to describe the I3(-)/I- concentration within a typical dye sensitized solar cell under steady-state conditions was derived. It includes the nanoporous TiO2 layer and a bulk solution with their different mobilities for the electrolyte species. Using typical parameters from the literature, it turned out that, despite the fact that the initial I- concentration is about 1 order of magnitude larger and the assumed diffusion coefficient is 1.3 times higher, the depletion of the I- concentration at the TiO2/FTO front contact happens to be in the same range as the depletion of the I3(-) concentration at the back contact. This stresses the importance of iodide in nanoporous environments for both the maximum attainable photocurrent and its role in the regeneration of the oxidized dye. Enhanced degradation rates might be related to poor iodide supply, since the oxidized state cannot be regenerated efficiently.     

Effect of additives on the photovoltaic performance of coumarin-dye-sensitized nanocrystalline TiO2 solar cells

The effects of deoxycholic acid (DCA) and 4-tert-butylpyridine (TBP) as additives on the photovoltaic performance of coumarin-dye-sensitized nanocrystalline TiO2 solar cells were investigated. DCA coadsorption improved both the photocurrent and photovoltage of the solar cells, even though it decreased the amount of dye adsorbed on the TiO2 electrode. The improved photocurrent may arise from suppression of the deactivation of the excited state via quenching processes between dye molecules or a more negative LUMO level of the dye in the presence of DCA, resulting in a high electron-injection yield from the dye into TiO2. The increased photovoltage is probably due to suppression of recombination between the injected electrons and I3- ions on the TiO2 surface (dark current). The addition of TBP to the electrolyte also markedly improved the photovoltage and fill factor of the solar cell, and consequently, the total conversion efficiency increased from 3.6% to 7.5%. FT-IR spectroscopy indicated that a large amount of TBP was adsorbed on the dye-coated TiO2 films in the presence of Li cations. This result suggests that TBP, like DCA, suppressed the dark current on the TiO2 surface, which resulted in the improved photovoltage.     

TiO2 band shift by nitrogen-containing heterocycles in dye-sensitized solar cells: a periodic density functional theory study

A density functional theory (DFT) method (periodic DMol3) with full geometry optimization was used to study the adsorption of nitrogen-containing heterocycles such as pyrazole, imidazole, 1,2,4-triazole, pyridine, pyrimidine, pyrazine, and 4-t-butylpyridine (TBP) on TiO2 anatase (101), (100), and (001) surfaces. All structures displayed a negative shift in the TiO2 Fermi level upon adsorption of N-containing heterocycles. Additionally, the heterocycles were examined as an additive in an I-/I3- redox electrolyte solution of dye-sensitized TiO2 solar cell. The DFT results indicated that the negative shift of TiO2 Fermi level was due to the adsorbate dipole moment component normal to the TiO2 surface plane, and corresponded to the enhanced open-circuit photovoltage (Voc) and the reduced short-circuit photocurrent density (Jsc) in a dye-sensitized solar cell.     

Effect of Surface Protonation on Device Performance and Dye Stability of Dye-sensitized TiO2 Solar Cell

A flat thin TiO₂ film was employed as the photo-electrode of a dye sensitized solar cell (DSSC), on which only a geometrical mono-layer of dye was attached. The effect of sur-face protonation by HCl chemical treatment on the performance of DSSCs was studied. The results showed that the short-circuit current Jsc increased significantly upon the HCl treatment, while the open-circuit voltage Voc decreased slightly. Compared to the untreated DSSC, the Jsc and energy conversion efficiency was increased by 31% and 25%, respectively, for the 1 mol/L HCl treated cell. TiO₂ surface protonation improved electronic coupling between the chemisorbed dye and the TiO₂ surface, resulting in an enhanced electron in-jection. The decreased open-circuit voltage after TiO₂ surface protonation was mainly due to the TiO₂ conduction band edge downshift and was partially caused by increased electron recombination with the electrolyte. In situ Raman degradation study showed that the dye stability was improved after the TiO₂ surface protonation. The increased dye stability was contributed by the increased electron injection and electron back reaction with the electrolyte under the open-circuit condition.     

Spatial electron distribution and its origin in the nanoporous TiO2 network of a dye solar cell

Dye solar cells have been investigated by charge carrier extraction under short and open circuit conditions and an illumination intensity equivalent to 1 sun (AM 1.5). Under short circuit conditions, a surprisingly high amount of charge carriers stored in the nanoporous TiO2 network has been observed. A theoretical model was developed to describe the charge transport in the nanoporous TiO2 network of a dye solar cell, and the spatial distribution of the electron concentration was calculated. These results were compared with the experimental data of charge carriers stored in the TiO2 network under short and open circuit conditions. We were able to conclude that under short circuit conditions, the electrochemical potential of the electrons in the region far from the electrode is up to 550-570 meV higher than that of the electrons at the front electrode. This internal voltage is the driving force across the nanoporous TiO2 film under short circuit conditions.     

电化学阻抗谱研究染料/Al2O3交替组装结构的光伏特性及作用机理

使用Al₂O₃和N3染料制备了一种交替组装的结构, 该结构能够提高染料敏化太阳能电池(DSCs)的开路电压(V_oc), 短路电流(J_sc)和转换效率(η). 为了研究(染料/Al₂O₃)交替组装结构的作用机理, 使用电化学阻抗谱技术分析了电池的界面电阻. 分析结果表明, 随着交替组装结构中(染料/Al₂O₃)单元的增加, 光阳极/染料/电解质界面的电阻降低, 电池性能随之提高. 基于电化学阻抗谱分析结果, 建立了一系列的等效电路模型, 从理论上解释了(染料/Al₂O₃)交替组装结构的作用机理.     

Efficiency enhancement in dye-sensitized solar cells using hierarchical TiO2 submicron size spheres as a light scattering layer

Journal of Solid State Electrochemistry - The photoanode of a dye-sensitized solar cell (DSSC), usually made with a nanoporous TiO2 semiconductor layer sensitized with N719 dye, plays a crucial...     

Dye-sensitized TiO2 Solid Solar Cell Using Poly （4-vinylphenyloxy-methyltriphenylamine） as Hole Transport Material

A dye-sensitized TiO2 solid solar cell, which contains poly(4-vinylphenyloxy-methyltriphenylamine) in hole transport layer (HTL) doped with LiSCN and methyl-hexyl-imidazolium iodide (MHImI), was oreoared. The solar cell shows that the conversion efficiency is 0.59%, Jsc is 3.03mA/cm^2, and Voc is 0.53V at 1 sun light intensity.     

Preparation of nanoporous MgO-coated TiO2 nanoparticles and their application to the electrode of dye-sensitized solar cells

Sol-gel-derived Mg(OH)(2) gel was coated onto TiO(2) nanoparticles, and the subsequent thermal topotactic decomposition of the gel formed a highly nanoporous MgO crystalline coating. The specific surface area of the electrode that was prepared from the core-shell-structured TiO(2) nanoparticles significantly increased compared with that of the uncoated TiO(2) electrode. The increase in the specific surface area of the MgO-coated TiO(2) electrode was attributed to the highly nanoporous MgO coating layer that resulted from the topotactic reaction. Dye adsorption behavior and solar cell performance were significantly enhanced by employing the MgO-coated TiO(2) electrode. Optimized coating of a MgO layer on TiO(2) nanoparticles enhanced the energy conversion efficiency as much as 45% compared to that of the uncoated TiO(2) electrode. This indicates that controlling the extrinsic parameters such as the specific surface area is very important to improve the energy conversion efficiency of TiO(2)-based solar cells.     

An alternative efficient redox couple for the dye-sensitized solar cell system

A series of new cobalt complexes [Co(LLL)(2)X(2)] were synthesized and evaluated as redox mediators for dye-sensitized nanocrystalline TiO(2) solar cells. The structure of the ligand and the nature of the counterions were found to influence the photovoltaic performance. The one-electron-transfer redox mediator [Co(dbbip)(2)](ClO(4))(2) (dbbip = 2,6-bis(1'-butylbenzimidazol-2'-yl)pyridine) performed best among the compounds investigated. Photovoltaic cells incorporating this redox mediator yielded incident photon-to-current conversion efficiencies (IPCE) of up to 80%. The overall yield of light-to-electric power conversion reached 8 % under simulated AM1.5 sunlight at 100 W m(-2) intensity and more than 4% at 1000 W m(-2). Photoelectrodes coated with a 2 microm thick nanoporous layer and a 4 microm thick light-scattering layer, sensitized with a hydrophobic ruthenium dye, gave the best results.     

十八硫醇自组装膜对TiO2光电氧化甲醇的敏化作用

纳米电极;甲醇光电氧化;十八硫醇自组装膜对TiO2光电氧化甲醇的敏化作用     

A strategy to increase the efficiency of the dye-sensitized TiO2 solar cells operated by photoexcitation of dye-to-TiO2 charge-transfer bands

Dye-sensitized nanoporous TiO2 solar cells (DSSCs) can be classified into two types, namely, Type-I and Type-II. Type-I DSSCs are the DSSCs in which electrons are injected from the adsorbed dyes by photoexcitation of the dyes followed by electron injection from the excited dyes to TiO2 (pathway A). Type-II DSSCs are the DSSCs in which electrons are injected not only by pathway A but also by direct one-step electron injection from the dyes to TiO2 by photoexcitation of the dye-to-TiO2 charge-transfer (DTCT) bands (pathway B). The DSSCs employing catechol (Cat) or its derivatives as the sensitizers have been the typical examples of Type-II DSSCs. However, their solar energy-to-electricity conversion efficiencies (eta) have never exceeded 0.7%, and the external quantum efficiencies (EQE) at the absorption maximums of the DTCT bands have never exceeded 10%. We found that the attachment of electron-donating compounds such as (pyridin-4-yl)vinyl and (quinolin-4-yl)vinyl, respectively, to Cat (designated as Cat-v-P and Cat-v-Q, respectively) leads to 2- and 2.7-fold increases, respectively, in eta, driven by large increases in short circuit current (Jsc). The EQE increased from 8.5 to 30% at 400 nm upon changing from Cat to Cat-v-P, at which only the DTCT band absorbs. In the case of the Cat-v-Q-sensitized DSSC, even the eta obtained by exciting only the DTCT band was higher than 1%. Interestingly, the illumination of only the DTCT band resulted in the increase of fill factor from 62.6% to 72.3%. This paper provides for the first time an insight into the strategy to increase the eta values of Type-II DSSCs.     

3-氨基丙基三甲氧基硅烷自组装提高染料敏化太阳能电池的效率

以3-氨基丙基三甲氧基硅烷(APTS)修饰的二氧化钛为负极制备的染料敏化太阳能电池在100 mW·cm^-2的模拟太阳光照下的短路电流、开路电压、光电转换效率分别为18.32 mA·cm^-2、775.9 mV、9.15%. 而没有经过ATPS修饰的电池三项性能参数分别为18.08 mA·cm^-2、749.9 mV、7.70%, 修饰后电池的光电转换效率提高了18.8%, 同时填充因子由0.57提高为0.64. 暗电流-电压曲线显示起始电压从-0.30 V变化到-0.40 V, 表明二氧化钛电极和电解液之间的暗反应得到了有效抑制, APTS作为阻挡层减少了二氧化钛电极表面的缺陷与表面态. 另外, 通过实验设计, 将APTS与染料层-层自组装于二氧化钛电极上, 通过X射线光电子能谱(XPS)研究了二氧化钛层、APTS、染料的作用形式. 定性与定量结果表明: APTS中的乙氧基部分脱除后形成了Si―O―Ti单桥或者双桥键, 钌染料cis-Ru(dcpyH₂)₂(SCN)₂通过分子中的部分―COOH与APTS中的―NH₂形成的静电作用力吸附在TiO₂电极上. 傅里叶变换红外(FT-IR)光谱的结果进一步证明了这种分子间作用.     

Y3Al5O12:Ce phosphors as a scattering layer for high-efficiency dye sensitized solar cells

Y(3)Al(5)O(12):Ce phosphors have been prepared and used as an effective scattering layer on top of a transparent layer of nanocrystalline TiO(2) for dye sensitized solar cells (DSSCs). The Y(3)Al(5)O(12):Ce scattering layer increases the photocurrent of DSSCs due to the enhanced light harvesting mainly via the improved light absorption and scattering. Under one sun illumination (AM 1.5G, 100 mW cm(-2)), a high efficiency of 7.91% was achieved for the cell with a Y(3)Al(5)O(12):Ce scattering layer, which is an increase of 13.5% compared to the cell without a scattering layer (6.97%).     

分级微纳结构TiO2空心球的制备及其在DSSC中的应用

以钛酸四丁酯为钛源,无水乙醇为溶剂,通过碳球模板法制备出直径为200nm、壳厚20～25nm的TiO2空心球（HS）.通过X射线衍射（XRD）、透射电子显微镜（TEM）、扫描电子显微镜（SEM）和N2吸附脱附等对产物的形貌、晶相组成、孔结构和紫外-可见光谱性质进行了表征,结果显示所制备的锐钛矿相TiO2空心微球是由初级结构纳米级TiO2晶粒构成的.将这种TiO2空心球应用于染料敏化太阳电池（DSSC）领域可以提高光阳极对光的散射.通过制备P25/HS-TiO2双层膜电极,相比单纯的P25纳米晶电极（Jsc=13.5mAcm？2,Voc=0.653V,FF=0.53,η=4.95%）可以得到更高的光电转化效率（Jsc=15.79mAcm？2,Voc=0.653V,FF=0.55,η=6.66%）.     

Significant efficiency improvement of the black dye-sensitized solar cell through protonation of TiO2 films

This paper describes the influence of acid pretreatment ofTiO2 mesoporous films prior to dye sensitization on the performance of dye-sensitized solar cells based on [(C4H9)4N]3[Ru(Htcterpy)(NCS)3] (tcterpy = 4,4',4"-tricarboxy- 2,2',2"-terpyridine), the so-called black dye. The HCl pretreatment caused an increase in overall efficiency by 8%, with a major contribution from photocurrent improvement. It is speculated, from the analysis of incident photon-to-electron conversion efficiency, UV-vis absorption spectra, redox properties of the dye and TiO2, and the impedance spectra of the dye-sensitized solar cells, that photocurrent enhancement is attributed to the increases in electron injection and/or charge collection efficiency besides the improvement of light harvesting efficiency upon HCl pretreatment. Open-circuit photovoltage (V(oc)) remained almost unchanged in the case of significant positive shift of flat band potential for TiO2 upon HCl pretreatment. The suppression of electron transfer from conduction band electrons to the I3- ions in the electrolyte upon HCl pretreatment, reflected by the increased resistance at the TiO2/dye/electrolyte interface and reduced dark current, resulted in a V(oc) gain, which compensated the V(oc) loss due to the positive shift of the flat band. Using the HCl pretreatment approach, 10.5% of overall efficiency with the black dye was obtained under illumination of simulated AM 1.5 solar light (100 mW cm(-2)) using an antireflection film on the cell surface.     

Double-layer coating of SrCO3/TiO2 on nanoporous TiO2 for efficient dye-sensitized solar cells

Surface modification plays a crucial role in improving the efficiency of dye-sensitized solar cells (DSSCs), but the reported surface treatments are in general superior to the untreated TiO(2) but inferior to the typical TiCl(4)-treated TiO(2) in terms of solar cell performance. This work demonstrates a two-step treatment of the nanoporous titania surface with strontium acetate [Sr(OAc)(2)] and TiCl(4) in order, each step followed by sintering. An electronically insulating layer of SrCO(3) is formed on the TiO(2) surface via the Sr(OAc)(2) treatment and then a fresh TiO(2) layer is deposited on top of the SrCO(3) layer via the TiCl(4) treatment, corresponding to a double layer of Sr(OAc)(2)/TiO(2) coated on the TiO(2) surface. As compared to the typical TiCl(4)-treated DSSC, the Sr(OAc)(2)-TiCl(4) treated DSSC improves short-circuit photocurrent (J(sc)) by 17%, open-circuit photovoltage (V(oc)) by 2%, and power conversion efficiency by 20%. These results indicate that the Sr(OAc)(2)-TiCl(4) treatment is better than the often used TiCl(4) treatment for fabrication of efficient DSSCs. Charge density at open circuit and controlled intensity modulated photocurrent/photovoltage spectroscopy reveal that the two electrodes show almost same conduction band level but different electron diffusion coefficient and charge recombination rate constant. Owing to the blocking effect of the SrCO(3) layer on electron recombination with I(3)(-) ions, the charge recombination rate constant of the Sr(OAc)(2)-TiCl(4) treated DSSC is half that of the TiCl(4)-treated DSSC, accounting well for the difference of their V(oc). The improved J(sc) is also attributed to the middle SrCO(3) layer, which increases dye adsorption and may improve charge separation efficiency due to the blocking effect of SrCO(3) on charge recombination.     

双链结构有机光敏染料的合成及性能

设计合成了2个含双D-π-A结构的新型有机光敏染料DP1和DP2,利用高分辨质谱(HRMS)、核磁共振氢谱及核磁共振碳谱对其结构进行了表征。 研究了2个染料的光物理和电化学性质,并将其应用于染料敏化太阳能电池(DSSCs)的制作中。 在100×10-3 W/cm2(AM 1.5) 模拟太阳光的照射下,由染料DP2所制备的敏化太阳能电池的光电转化效率为4.10%;开路电压(Voc)、短路电流密度(Jsc)和填充因子(FF)分别为0.63 V、8.59×10-3 A/cm2和0.76。 而在同等条件下,由染料DP1所制作的染料敏化电池光电转化效率为3.83%。