2015 Fiscal Year Research-status Report
低電荷注入障壁に着目した近赤外領域に高い光電変換効率を持つ色素に関する研究
| Project/Area Number |
26410206
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| Research Institution | Kyushu Institute of Technology |
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Principal Investigator |
PANDEY SHYAM S. 九州工業大学, 生命体工学研究科(研究院), 准教授 (60457455)
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| Co-Investigator(Kenkyū-buntansha) |
早瀬 修二 九州工業大学, 生命体工学研究科(研究院), 教授 (80336099)
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| Project Period (FY) |
2014-04-01 – 2017-03-31
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| Keywords | Structural optimization / TD-DFT calculations / Far-red dye sensitizers / Squaraine dyes / Energy barrier mapping / DSSCs |
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| Outline of Annual Research Achievements |
Implementation of combined theoretical and experimental approaches were attempted using theoretical calculations by Gaussian program and far-red sensitive squaraine dyes. Some of the potential sensitizers were not only subjected to the synthesis followed by their photophysical characterizations but also subjected to photovoltaic application by fabricating the dye-sensitized solar cells. In the fiscal year 2015 two papers has been published in the international journals and 7 presentations were made in the international and domestic conferences.
In order to develop low band gap NIR dyes, information about fine control of energetics is highly desired. It has been found that it is possible to control the energy level at 0.1 eV level by nature and positioning of the substituents only with in the same molecular framework which has been published in the "Journal of Nanoscience and Nanotechnology".
Aiming towards mapping of the energetics to determine the minimum possible energy barrier for electron injection, efforts were directed by taking far-red squaraine dyes in to consideration. It has been found that it is possible not only to predict the experimental energy of HOMO with in ± 0.1 eV and but also their absorption maximum with in the 30-40 nm by utilizing suitable calculation parameters. Apart from this, it has also been demonstrated that it is possible to have the photon harvesting in the far-red region with a minimum energy barrier of 0.15 eV. Such results and observation have been published in the international journal, "Solar Energy Materials and Solar Cells".
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Several far-red sensitizing squaraine dyes were designed using Gaussian program package taking TD-DFT under 6-311G basis set along with the synthesis and photophysical characterizations. A perusal of the experimental and results pertaining to the calculation of their energy band gap, HOMO/LUMO energies and electronic absorption spectra revealed that functionals like LSDA and MPW1 were able accurately predict the HOMO energy level within the accuracy of± 0.1 eV. On the other hand, LSDA functional was able to accurately predict the absorption maximum with a small difference of 30-50 nm only as compared to the experimental data. At the same time, utilization of PCM mode in TD-DFT and B3PW91 functional gives comparative values of the results in terms of the energy of HOMO and absorption maximum as obtained by gas phase calculations using LSDA but energy band gap and energy of LUMO were rather more accurate but needs relatively higher computation cost.
Efforts were also directed to determine the minimum energy barriers for electron injection from excited dye to TiO2 conduction band and regeneration of oxidized dyes from iodine based redox electrolyte. Implementing these combined theoretical and experimental approaches, it has been found that it is possible to inject the electron and regenerate dye oxidized dye with minimum energy barrier of 0.15 eV and 0.12 eV, respectively. This indicates that using these class of sensitizers it possible to design NIR dyes having minimum energy band gap of 1.17 eV having capability of photon harvesting up to 1050 nm.
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| Strategy for Future Research Activity |
Our combined theoretical and experimental results on far-red sensitive dyes reveal that optimum functionals, alkyl chain length, nature of substituents and their suitable positioning not only affects the energies but also the photovoltaic performance. As a next stage efforts will be directed to design and develop near infra-red (NIR) dyes having absorption maximum >750 nm by introducing extended pi-conjugated frameworks.
In parallel, some of the potential NIR sensitizers based on the feedback from our computational results, will also be synthesized and subjected to photophysical characterizations such as estimation of energies of HOMO & LUMO, energy band gap and electronic absorption spectra. HOMO energy level will be experimentally determined using photo-electron yield spectroscopy and cyclic voltammetry. Energy band gap will be experimentally estimated taking the help of electronic absorption and fluorescence emission spectroscopies. Extension of pi-conjugation quite often leads to reduced fluorescence life-time which competes with the electron injection kinetics, therefore, their fluorescence life-time will also be estimated prior to their implementation as sensitizer of DSSCs.
To circumvent such problems, efforts will also be directed design and develop novel far-red sensitizers with high open circuit voltage in order to achieve overall high efficiency using alternate cobalt based electrolytes. Finally, photovoltaic characterizations after DSSC fabrications will also be made to delineate the structure with the functions under investigation.
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| Causes of Carryover |
Some of the chemicals could not be purchased due to their possible delivery with in the fiscal year 2015
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| Expenditure Plan for Carryover Budget |
This will be used for consumables in the fiscal year 2016
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Research Products
(9 results)
