Structure鈥揚roperty Relationships for Exciton and Charge Reorganization Energies of Dipolar Organic Semiconductors: A Combined Valence Bond Self-Consistent Field and Time-Dependent Hartree-Fock and DF

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• 作者：Charlotte Br眉ckner ; Christof Walter ; Matthias Stolte ; Beno卯t Bra茂da ; Klaus Meerholz ; Frank W眉rthner ; Bernd Engels
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：August 6, 2015
• 年：2015
• 卷：119
• 期：31
• 页码：17602-17611
• 全文大小：518K
• ISSN：1932-7455

文摘

We present an analysis of the optoelectronic properties of merocyanine dyes by means of valence bond self-consistent field (VBSCF), time-dependent Hartree-Fock (TD-HF), density functional theory (DFT), and high-level ab initio calculations. The electronic structure of merocyanines can be described as a superposition of two resonance structures, a neutral one and a zwitterionic one. Calculated valence bond (VB) weights for these resonance structures demonstrate the importance of strong accepting groups when increasing the weight of the zwitterionic structures of different merocyanines. The dependence of exciton and charge reorganization energies on VB weights鈥?composition is analyzed, demonstrating that the special case of equal contributions of both structures, the so-called cyanine limit, goes along with minimal exciton and charge reorganization energies. For the latter, it is shown that the external (outer-sphere) reorganization energy plays a crucial role. Furthermore, a careful investigation of the excited-state behavior of merocyanines indicates that a possible excited-state torsion might be another important parameter for merocyanine-based optoelectronic devices, whereas internal (inner-sphere) charge reorganization energies of a variety of merocyanines are in a typical range for molecular semiconductors.