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莲花如梦木虫之王 (文坛精英)
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[求助]
求关于染料敏化太阳能电池的翻译
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Understanding electron-transfer (ET) processes in dye-sensitized solar cells (DSSCs) is crucial to improving their device performance. Recently, covalent attachment of dye molecules to mesoporous semiconductor nanoparticle films via molecular linkers has been employed to increase the stability of DSSC photoanodes. The power conversion efficiency (PCE) of these DSSCs, however, is lower than DSSCs with conventional unmodified photoanodes in this study. Ultrafast transient absorption pump–probe spectroscopy (TAPPS) has been used to study the electron injection process from N719 dye molecules to TiO2 nanoparticles (NPs) in DSSC photoanodes with and without the presence of two silane-based linker molecules: 3-aminopropyltriethoxysilane (APTES) and p-aminophenyltrimethoxysilane (APhS). Ultrafast biphasic electron injection kinetics were observed in all three photoanodes using a 530 nm pump wavelength and 860 nm probe wavelength. Both the slow and fast decay components, attributed to electron injection from singlet and triplet excited states, respectively, of the N719 dye to the TiO2 conduction band, are hindered by the molecular linkers. The hindering effect is less significant with the APhS linker than the APTES linker and is more significant for the singlet-state channel than the triplet-state one. Electron injection from the vibrationally excited states is less affected by the linkers. The spectroscopic results are interpreted on the basis of the standard ET theory and can be used to guide selection of molecular linkers for DSSCs with better device performance. Other factors that affect the efficiency and stability of the DSSCs are also discussed. The relatively lower PCE of the covalently attached photoanodes is attributed to the multilayer and aggregation of the dye molecules as well as the linkers. On the basis of the TAPPS measurements, we propose that the electron injection from the excited states of N719 dye to TiO2 semiconductor conduction band occurs via two channels: a fast channel (tens of femtoseconds) from the singlet states of N719 and a slow channel (～1−10 ps) from its triplet states. The electron injection process is hindered by linker molecules APTES and APhS that are covalently attached to the N719 dye molecules. The magnitude of the hindering effect depends on both the spin-multiplicity of the excited electronic states of the dye and molecular vibrations. The hindering effect is more significant for singlet excited-state molecules than molecules in triplet states. Electron injection from vibrationally excited triplet-state molecules is less vulnerable to the hindering effect. Electron injection processes in the FTO/TiO2/APhS/N719 photoanodes are faster than in the FTO/TiO2/APTES/N719 photoanode because the APhS molecule is more conductive due to its aromaticity. Suitable choice of linker molecules is therefore important in producing DSSCs that have both long stability and high PCE. The stability of the phtotoanodes is significantly increased upon covalent attachment, attributed to the protective environment provided by the linker molecules to the SCN ligands.9 Although the molecular linkers slow the electron injection process, it is still orders of magnitude faster than the charge recombination to dye molecules and the electrolyte as well. The relatively slower electron injection rate is therefore not the reason for the observed lower PCE of the FTO/TiO2/APTES/N719 photoanode compared with the conventional one. The relatively lower PCE of the covalently attached photoanodes is mainly due to the multilayer and aggregation of the dye molecules above the covalently bonded ones in addition to the possible multilayer formation of the linker itself. TAPPS results show that the FTO/TiO2/APhS/N719 photoanode has better coverage of monolayer dye molecules than the FTO/TiO2/APTES/N719 photoanode. A higher PCE is therefore expected. Monolayer coverage of linkers on semiconductor metal oxide is necessary for improving PCE of such devices, as shown recently.9 When the soaking time in dye solution was controlled to avoid multilayers, PCE of the FTO/ TiO2/APTES/N719 photoanode was increased to 6.0 ± 1.0%, very close to that of the conventional one (6.5 ± 0.9%). Modification of the covalently attached photoanodes, for instance, with gold nanoparticles, can further improve the performance of DSSCs with chemically functionalized photoanodes and will be the subject of future work. 专业性太强了，不知道怎么组织语言（想知道使用APhS 改性后优异性能的具体体现） |
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2楼2016-01-12 16:08:04
莲花如梦
木虫之王 (文坛精英)
- 应助: 28 (小学生)
- 金币: 60808.1
- 散金: 812
- 红花: 163
- 帖子: 19512
- 在线: 1381.7小时
- 虫号: 1246510
- 注册: 2011-03-27
- 性别: GG
- 专业: 元素有机化学
3楼2016-01-13 07:13:20
4楼2016-01-13 09:35:59
莲花如梦
木虫之王 (文坛精英)
- 应助: 28 (小学生)
- 金币: 60808.1
- 散金: 812
- 红花: 163
- 帖子: 19512
- 在线: 1381.7小时
- 虫号: 1246510
- 注册: 2011-03-27
- 性别: GG
- 专业: 元素有机化学
5楼2016-01-13 12:30:41
6楼2016-01-15 14:41:46
