| 研究実績の概要 |
The main focus was directed for the theoretical calculations and optimization of calculation parameters using Gaussian program package. Some of the model far-red sensitive squaraine dyes were also synthesized and characterized and subjected to photovoltaic applications after fabrication of dye-sensitized solar cells to check the validity of calculated results. In terms of the research achievements for the fiscal year 2014 two papers has been published in the international journals and two presentations were made in the international conferences.
Results pertaining the theoretical molecular design, calculation and comparison of the obtained result with experimental values for the same model far-red sensitive dye that an appropriate functional and basis set is important depending on the physical properties of interest to be taken under consideration and the work was published in the Journal of Engineering Science and Technology.
One of aim proposed to map the energetics of the NIR sensitizers which needs a fine control of energy level by molecular design, four model fa-red sensitizers were designed and results on the theoretical calculation and the corresponding experimentally observed values reveal that it is possible to control the energy level by 0.1 eV by nature and position of the substituents keeping the same main molecular framework. Such findings has been published in the Journal of Nanoscience and Nanotechnology.
|
| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
First of all Gaussian program was used to assist the molecular design using a model unsymmetrical squaraine dye was which was designed and subjected structural optimization and calculation of electronic absorption spectra. To make a balance between computation cost and accuracy, density functional theory (DFT) under 6-311G basis set was utilized aiming to get the optimum functional for the prediction of energy of the HOMO and LUMO along with absorption maximum using TD-DFT. In parallel, the designed sensitizers were synthesized, characterized and subjected to photophysical characterizations.
Theoretical calculations reveal that a logical selection of optimum functional is required depending on the physical properties under consideration. For example, functionals like LSDA, PBE1 and MPW1 gives relatively better similarity with the experimentally determined HOMO energy level. On the other hand, functional like LSDA, HCTH, THCTH and BPV86 gives better result for the absorption maximum. At the same time, if we are interested in the calculation of energy band gap, B3LYP and B3PW91 are found to be optimum.
In order to fine tune and have a control of energetics, four model squaraine dyes bearing same pi-conjugated frame and alkyl chain length were designed based on theoretical calculations, synthesized, characterized and used as sensitizers for the fabrication of DSSC. Results have revealed that simply by creating molecular asymmetry and positional variation of substituents, itis possible to control the energy level of the sensitizers for electron injection at 0.1 eV level.
|
| 今後の研究の推進方策 |
After the feedback from the theoretical calculations using model far-red sensitizers about the optimal functionals and our previous report that alkyl chain length not only affects the energies of HOMO and LUMO but the photovoltaic performance also, it is realized to systematically design model far-red sensitive dyes with systematically varying energetics. To achieve this, model dyes with decreasing energy level of LUMO for electron injection and increasing energy level of HOMO for dye regeneration up to minimum possible energy barrier will be designed by introducing electron withdrawing and donating substituents keeping main -conjugated framework the same.
In parallel, potential model sensitizers based on feedback of computational results using Gaussian program will 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 estimated taking the help of electronic absorption and fluorescence emission spectroscopy. Photovoltaic characterizations after DSSC fabrications will also be made to delineate the structure with the functions under consideration. The basic idea is to map minimum possible energy barrier for electron injection and dye-regeneration. Such information will be helpful in designing novel NIR dyes with relatively lower energy band gaps having photon harvesting in the extended high wavelength region.
|
