Theoretical Study of Singlet Fission in Polyacene Dimers
Date Issued
2014
Date
2014
Author(s)
Lin, Shih-Kai
Abstract
Because of the promising potential in the high efficiency solar cell, singlet exciton fission, the molecular analogue of multiexciton generation resulting in two independent triplet excitons by absorbing a single photon, has attracted
increasing attention recently. Although the striking research works are advancing, the mechanism of SF is still controversial, and some open questions remain, e.g., the key parameters manipulating the occurrence of SF and the excited state wavefunctions involved in it. From an electronic structure point of view, we construct an approximate diabatic basis to unambiguously interpret the character of the excited states, by applying the restricted active space
configuration interaction single and double approach to show the importance of considering multi-configuration effects in polyacene dimers, especially the key role of double-excitation configurations. Using a three-state model, strong superexchange effective coupling and the near degeneracy condition that explain the ultrafast SF mechanism are obtained. We demonstrate that a crucial factor is the energetic position of the charge transferred diabatic state,
which remarkably controls the amplitude of the effective coupling. Therefore, in addition to the near degeneracy of the lowest lying singlet exciton and the double-triplet state, we conclude that the lowering of the charge transferred diabatic state energy should also be considered as a key factor for the design of hign efficiency SF materials. Finally we show that dominant interactions
controlling SF efficiency in a dimer can be decomposed into Conlomb interaction between monomer molecular orbitals. Trough molecular orbital based analysis of configuration interactions involved in the SF process, the driving
force of SF can be determined from the relative orientation of monomers, providing an effective method to survey potential molecules and further guideline to the design principle of high SF dye-sensitizing materials.
Subjects
交替烴
多並苯
發色團設計
超快光譜
激發子分裂
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-103-R01223138-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):650f17ce5a2b43f0038ab21563be2eaa