Effect of iodine addition on solid-state electrolyte LiI/3-hydroxypropionitrile (1:4) for dye-sensitized solar cells

It was observed that the ionic conductivity of the solid-state electrolyte LiI/3-hydroxypropionitrile (HPN) = 1:4 (molar ratio) decreased dramatically with increasing iodine (I(2)) concentration, which differs from the conduction behavior of the Grotthuss transport mechanism observed in liquid or gel electrolytes. The short-circuit photocurrent density (J(sc)) of the dye-sensitized solar cell (DSSC) based on this electrolyte system increases with increasing I(2) concentration until LiI/I(2) is 1:0.05 (molar ratio). Beyond this limitation, the J(sc) decreases. At low I(2) concentrations (I(2)/LiI < or = 0.05), the J(sc) is mainly affected by the diffusion of I(3)(-). An increase of the I(2) concentration leads to the enhancement of the diffusion of I(3)(-) and an increase of the J(sc). At high I(2) concentrations (I(2)/LiI > 0.05), the factors, including the increased light absorption by the I(3)(-), the increased recombination of electrons at the photoanode with I(3)(-), and the reduced ionic conductivity of the electrolyte, lead to a decrease of J(sc). At the same time, the open-circuit voltage (V(oc)) of the DSSC decreases monotonically with the ratio of I(2)/LiI due to increased dark current in the DSSC. The increased absorption of visible light by the electrolyte, the enhanced dark current, and the reduced ionic conductivity of the electrolyte contribute to the performance variation of the corresponding solid-state DSSC with increasing I(2) concentration.     

Polymer-in-salt like conduction behavior of small-molecule electrolytes

Abnormal salt content dependence of conductivity is observed in solid electrolytes exclusively composed of small molecules of 3-hydroxypropionitrile (HPN) and lithium iodide (LiI) induced by reinforced hydrogen bonding and formation of ionic clusters at high salt content.     

染料敏化太阳电池用聚合物电解质

综述了本研究小组近年来用于染料敏化太阳电池中聚合物电解质的研究概况.设计合成了几类性能优良的聚合物电解质,较好地改进了液体电解质染料敏化太阳电池(DSSC)的使用稳定性,研究结果具有实际应用的价值,并提出了此领域研究今后的发展方向.     

Effect of lithium iodide addition on poly(ethylene oxide)-poly(vinylidene fluoride) polymer-blend electrolyte for dye-sensitized nanocrystalline solar cell

The effect of lithium iodide concentration on the conduction behavior of poly(ethylene oxide)-poly(vinylidene fluoride) (PEO-PVDF) polymer-blend electrolyte and the corresponding performance of the dye-sensitized solar cell (DSSC) were studied. The conduction behavior of these electrolytes was investigated with varying LiI concentration (10-60 wt % in polymer blend) by impedance spectroscopy. A "polymer-in-salt" like conduction behavior has been observed in the high salt concentration region. The transition from "salt-in-polymer" to "polymer-in-salt" conduction behavior happened at the salt content of 23.4 wt %, which is much lower than 50 wt % as generally reported. The electrolyte shows the highest ionic conductivity (approximately 10(-3) S cm(-1)) at the salt concentration above 23.4 wt %. From the evaluation of salt effect on the performances of corresponding DSSC, we find that increasing LiI concentration leads to increased short-circuit photocurrent density (Jsc) caused by enhanced I3(-) diffusion up to an LiI content of 28.9 wt %. Above this limitation, the Jsc decreases as a result of increased charge recombination caused by the further increased I3(-) concentration. The open-circuit voltage (Voc) increases gradually with LiI concentration owing to the enhanced I(-) content in DSSC. The optimized conversion efficiency is obtained at a salt content of 28.9 wt % in the "polymer-in-salt" region, with high ionic conductivity (1.06 x 10(-3) S cm(-1)). Based on these facts, we suggest that the changes of conduction behavior and the changes of I3(-) and I(-) concentrations in the electrolytes contribute to the final performance variation of the corresponding DSSC with varying LiI concentration.     

Cheap and environmentally benign electrochemical energy storage and conversion devices based on AlI3 electrolytes

Cheap and environmentally benign electrochemical energy conversion and storage devices, including a dye-sensitized solar cell (DSSC) using an AlI3-ethanol electrolyte and a new Al/I2 primary battery, are reported. The AlI3-ethanol electrolyte can be prepared simply by adding aluminum powder and iodine into ethanol at ambient conditions. The DSSC using this AlI3-ethanol electrolyte achieved an energy conversion efficiency of 5.9% at AM 1.5 (100 mW/cm-2). In the Al/I2 battery, AlI3 is formed spontaneously when aluminum and iodine electrodes are brought into contact at room temperature. Then I- anions transport across the AlI3 solid electrolyte for further electrochemical reactions.     

Dye-sensitized solar cells employing amphiphilic poly(ethylene glycol) electrolytes

Poly(ethylene glycol) (PEG) was modified with a long alkyl acid to produce a self-organized amphiphilic polymer (amPEG). FT-IR and NMR spectroscopies confirmed the amPEG synthesis. This polymer was complexed with lithium iodide (LiI) and 1-methyl-3-propylimidazolium iodide (MPII) to prepare polymer electrolytes to be applied to dye-sensitized solar cells (DSSC). FT-IR studies showed that upon the addition of litium salt the free ether and ester carbonyl bands shifted towards lower wavenumbers, indicating the complexation of Li ions with oxygens on the amPEG. Alkylation and salt introduction reduced PEG crystallinity, as characterized by wide angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC). The ionic conductivities of the polymer electrolytes increased with increasing salt concentrations, and the energy conversion efficiency of DSSC reached 2.6% at 100 mW cm^?2 for amPEG/MPII system which is higher than amPEG/LiI. This may be due to the higher mobility of MPII ion than the lithium ion in the polymer electrolyte. The interfacial properties between electrolytes and electrodes were investigated using field-emission scanning electron microscopy (FE-SEM) and electrochemical impedance spectroscopy (EIS).     

An alternative electrolyte based on acetylacetone–pyridine–iodine for dye-sensitized solar cells

We prepared a new organic electrolyte by the reaction among acetylacetone, pyridine and iodine in 3-methoxypropionitrile. The UV–Visible spectra, conductivity measurement and ESI mass spectra were used to study this electrolyte. It was suggested that the quaternization reaction of pyridine took place in this electrolyte solution and two kinds of pyridinium iodide were formed. The efficiency of dye-sensitized solar cells (DSCs) using this electrolyte reaches 6.72%, which is higher than that of DSCs using LiI electrolyte and methylpropylimidazolium iodide electrolyte. It implies that these pyridinium iodides are effective alternative component of iodide for the electrolytes of DSCs. As this organic iodide electrolyte was in situ synthesized based on iodine instead of alkyl iodide, it will be cost-effective and facilitative for the production of DSCs.     

A novel composite polymer electrolyte containing room-temperature ionic liquids and heteropolyacids for dye-sensitized solar cells

A novel composite polymeric gel comprising room-temperature ionic liquids (1-butyl-3-methyl-imidazolium-hexafluorophosphate, BMImPF₆) and heteropolyacids (phosphotungstic acid, PWA) in poly(2-hydroxyethyl methacrylate) matrix was successfully prepared and employed as a quasi-solid state electrolyte in dye-sensitized solar cells (DSSCs). These composite polymer electrolytes offered specific benefits over the ionic liquids and heteropolyacids, which effectively enhanced the ionic conductivity of the composite polymer electrolyte. Unsealed devices employing the composite polymer electrolyte with the 3% content of PWA achieved the solar to electrical energy conversion efficiency of 1.68% under irradiation of 50 mW cm⁻² light intensity, increasing by a factor of more than three compared to a DSSC with the blank BMImPF₆-based polymer electrolyte without PWA. It is expected that these composite polymer electrolytes are an attractive alternative to previously reported hole transporting materials for the fabrication of the long-term stable quasi-solid state or solid state DSSCs.     

Ionic Liquid Based Electrolyte with Mesoporous Silica SBA-15 as Framework for Quasi-solid-state Dye-sensitized Solar Cells

Quasi-solid-state electrolytes were fabricated with mesoporous silica SBA-15 as a framework material. Ionic conductivity measurements revealed that SBA-15 can enhance the conductivity of the quasi-solid-state electrolyte. The diffusion coefficients of polyiodide ions such as Ⅰ3ˉ and Ⅰ5ˉ which were confirmed by Raman spectroscopic measurement, were about twice larger than that of I-. The optimized photoenergy conversion efficiency of dye-sensitized solar cells （DSSC） with the quasi-solid-state electrolyte was 4.3% under AM 1.5 irradiation at 75 mW·cm^-2 light intensity.     

聚乙烯吡咯烷酮基碘凝胶电解质的制备及在染料敏化太阳能电池中的应用

采用聚乙烯吡咯烷酮(PVP)和聚偏氟乙烯(PVDF)为凝胶剂, 以碘化锂和碘单质为碘源, 碳酸乙烯酯(EC)和碳酸丙烯酯(PC)为溶剂, 制备了染料敏化太阳能电池(DSSCs)用凝胶聚合物电解质(GPE). 使用拉曼光谱、 循环伏安曲线和交流阻抗谱等对GPE进行表征. 结果表明, 聚合物的配比与浓度及碘与碘化锂比例对该电解质性能有很大影响, 当聚合物质量分数为10%、 PVP与PVDF质量比为80∶20、 I₂浓度为0.042 mol/L且LiI与I₂摩尔比为30∶1时, 制备的GPE在室温下电导率达最大值(3.27 mS/cm). 使用该GPE组装的DSSCs在100 mW/cm²的模拟太阳光照射下, 开路电压为0.64 V, 短路电流为13.6 mA/cm², 填充因子为0.595, 能量转化效率为5.18%, 并在30 d内表现出了良好的稳定工作性能.     

Synthesis of copolymer electrolytes based on polysiloxane and their high temperature durability analysis for solvent-free dye-sensitized solar cells

The present work develops a new type of solvent-free copolymer electrolyte based on polysiloxane for dye-sensitized solar cells (DSSCs). The electrolyte is characterized by conductivity measurements, hydrogen-1 nuclear magnetic resonance spectroscopy, rheology, and DSSC performance. Repeated units of the ethylene oxide on methylhydrosiloxane show plasticizing effects and enhanced durability of the DSSCs. DSSC employing the polysiloxane electrolytes show no energy conversion efficiency decay after 16 days test at room temperature and yields a conversion efficiency of 1.5% during long-term stability measurement at 90 °C under white light irradiation of 100 mW cm⁻². The new solvent-free polysiloxane copolymer electrolyte can be good candidate for next generation DSSC.     

Stepped light-induced transient measurements of photocurrent and voltage in dye-sensitized solar cells: application for highly viscous electrolyte systems

To measure electron diffusion coefficients (D) and electron lifetimes (tau) of dye-sensitized solar cells (DSC), we introduced stepped light-induced transient measurements of photocurrent and voltage (SLIM-PCV), which can simplify the optical setup and reduce measurement time in comparison to conventional time-of-flight and frequency-modulated measurements. The method was applied to investigate the influence of the viscosity of a thermally stable high-boiling-point solvent on the energy conversion efficiency of DSCs. By systematic study of the influence of the viscosity, the species of cations as the counter charge of I(-)/I(3)(-), and the concentrations of electrolytes, we concluded that a lower dye cation reduction rate due to slower iodine diffusion is a limiting factor for a highly viscous electrolyte system. On the other hand, comparable values of D and increased values of tau were observed in a highly viscous electrolyte. By employing 0.5 M TBAI and 0.05 M I(2) in propylene carbonate, the efficiency of the DSC became comparable to that of a DSC using conventional electrolytes consisting of LiI, imidazolium iodide, and 4-tert-butylpyridine in methoxyacetonitrile. The simultaneous evaluation of D and tau through the appropriately simple measurement realizes fast optimization of the efficient and reliable DSC composed of thermally stable but often viscous electrolytes.     

Quasi-solid-state dye-sensitized solar cells assembled by in-situ chemical cross-linking at ambient temperature

Cross-linked gel polymer electrolytes containing aluminum oxide nanoparticles are successfully prepared using in-situ chemical cross-linking at room temperature after injection of the gel precursor into a dye-sensitized solar cell (DSSC). This makes it possible to directly solidify the electrolyte in the cell without leakage of solvent and to maintain close interfacial contact with the porous TiO₂ electrode. The quasi-solid-state DSSC assembled with gel polymer electrolyte containing 20 wt.% Al₂O₃ particles yields an overall conversion efficiency of 5.25% under AM 1.5 illumination at 100 mW cm^{− 2}.     

染料敏化纳米薄膜太阳电池电解质的优化

探讨了小面积染料敏化纳米薄膜太阳电池放大到大面积太阳电池组件时,各种电解质体系对电池性能的影响,综合优化了各种电解质的性能,同时与大面积电池(0.8cm×18cm)制作相结合,获得符合电池各种性能要求的最佳配比的电解质体系.光电转换效率可达到6.48%.     

Quasi‐solid‐state dye‐sensitized solar cells containing P (MMA‐co‐AN)‐based polymeric gel electrolyte

Quasi‐solid state dye‐sensitized solar cells (QS‐DSSC) containing poly (methyl methacrylate‐co‐acrylonitrile) [P (MMA‐co‐AN)] gel electrolytes were fabricated. By tuning AN molar percentage in P (MMA‐co‐AN), the optimized polymeric gel electrolyte for fabricating QS‐DSSC can be obtained. QS‐DSSC containing polymeric gel electrolyte with 45 mol.% AN in P(MMA‐co‐AN) shows higher energy conversion efficiency than that of QS‐DSSCs containing polymeric gel electrolytes with either pure PMMA or PAN. So it presents an effective way to improve the photovoltaic performance of QS‐DSSC by tuning the components of polymeric gelling agent. Copyright © 2010 John Wiley & Sons, Ltd.     

金属配合物Cd（phen）2（NO3）（NO2）对ZnO光阳极的敏化特性

采用具有紫外光区吸收的金属配合物Cd(phen)2(NO3)(NO2)和N719对ZnO光阳极进行共敏化.结果表明,配合物能够对ZnO光阳极进行共敏化,同时被电解液还原再生,共敏化增加电池对光的吸收,电池光电流密度增加63%,共敏化降低了电池各个界面电阻,有利于电子在界面的传输,电池的光电转换效率提高了37%.     

An all-solid-state dye-sensitized solar cell-based poly(N-alkyl-4-vinyl-pyridine iodide) electrolyte with efficiency of 5.64%

Using poly(N-methyl-4-vinyl-pyridine iodide), N-methyl-pyridine iodide and iodine, a solid polymer electrolyte with conductivity of 6.41 mS/cm is prepared. On the basis of a solid polymer electrolyte, a conducting graphite layer, a KI block layer, and a vacuum assembling technique, we achieve an all-solid-state dye-sensitized solar cell with total photoelectric conversion efficiency of 5.64% under AM 1.5 simulated solar light (100 mW/cm2) illumination.     

P(VDF-HFP)基凝胶电解质染料敏化纳米TiO2薄膜太阳电池

采用循环伏安法(CV)研究了凝胶电解质中I₃-/I-氧化还原行为,凝胶电解质中I₃-/I-的表观扩散系数和相应的稳态扩散电流明显低于液体电解质.通过对阴/阳离子的结合能和孔穴阻塞作用的研究解释了凝胶电解质电导率较液体电解质发生变化的原因.制备的凝胶电解质电池具有较高的光电转换效率(6.6%),其短路电流密度(Jsc)仅比液体电解质电池低0.3-0.4 mA/cm²,电池效率也仅低约0.6%.     

Enhancement of photocurrent of polymer‐gelled dye‐sensitized solar cell by incorporation of exfoliated montmorillonite nanoplatelets

Poly(n‐isopropylacrylamide) (PNIPAAm) and its nanocomposite with exfoliated montmorillonite (MMT) were prepared by soap‐free emulsion polymerization and individually applied to gel the electrolyte systems for the dye‐sensitized solar cells (DSSCs). Each exfoliated MMT nanoplatelet had a thickness of ～ 1 nm, carried ～ 1.8 cation/nm², and acted like a two‐dimensional electrolyte. The DSSC with the LiI/I₂/tertiary butylpyridine electrolyte system gelled by this polymer nanocomposite had higher short‐circuit current density (J_sc) compared to that gelled by the neat PNIPAAm. The former has a J_sc of 12.6 mA/cm², an open circuit voltage (V_oc) of 0.73 V, and a fill factor (FF) of 0.59, which harvested 5.4% electricity conversion efficiency (η) under AM 1.5 irradiation at 100 mW/cm², whereas the latter has J_sc = 7.28 mA/cm², V_oc = 0.72 V, FF = 0.60, and η = 3.17%. IPCE of the nanocomposite‐gelled DSSC were also improved. Electrochemical impedance spectroscopy of the DSSCs revealed that the nanocomposite‐gelled electrolytes significantly decreased the impedances in three major electric current paths of DSSCs, that is, the resistance of electrolytes and electric contacts, impedance across the electrolytes/dye‐coated TiO₂ interface, and Nernstian diffusion within the electrolytes. The results were also consistent with the increased molar conductivity of nanocomposite‐gelled electrolytes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 47–53, 2008     

染料敏化纳米薄膜太阳电池中DMPII浓度的优化

利用超微铂电极和循环伏安法及电化学阻抗谱研究了在1,2-二甲基-3-丙基咪唑碘(DMPII)的3-甲氧基丙腈(MePN)溶液中I₃^－和I^－的氧化还原行为，并对比了由不同浓度的I2和DMPII组成的电解质溶液，其染料敏化纳米薄膜太阳电池(DSCs)的光伏性能. 发现以MePN为溶剂，含1.0 mol•dm^-3 DMPII、0.12 mol•dm^-3 I2、0.10 mol•dm^-3 LiI和0.50 mol•dm^-3 4-叔丁基吡啶的电解质溶液，其DSCs的短路光电流密度为16.67 mA•cm^-3、开路电压为0.69 V、填充因子为0.70、光电转换效率达8.08%.