Level alignment, charge transfer, and optical absorption of organic photovoltaics using LCAO-TDDFT-k-ω

Silicon-based pn-junction solar cells have reached their theoretical efficiency limits. For this reason, alternative optically active materials are of interest, as is the case for organic photovoltaics (OPVs), which promise more efficient, ecological, and economical solar cells. This project contributes to the computational design of OPVs and the understanding of the donor-acceptor excitonic process by modeling their optical absorption spectra. We applied a highly efficient linear combination of atomic orbitals within time-dependent density functional theory in the reciprocal space and frequency domains (LCAO-TDDFT-k-ω) that, compared with DFT and G0W0-BSE methods, allowed us to understand the excitonic process for macromolecular systems via an enhanced computational performance. Thus, LCAO-TDDFT-k-ω offered the possibility to accurately describe the optical absorption and level alignment for complex OPV-based systems. In this research, we focused on chlorophyll types (Chl a/b) as donor systems, highlighting their π-delocalized orbitals and central magnesium atom for efficient charge transfer and enhanced excited state lifetime. For the acceptor, SWCNTs, which exhibit properties like adjustable band gaps and high optical absorbance. The project successfully identified that the OPV-candidate formed by Chla/b@SWCNT(n, m) was a stable system, determined the optimal chirality of SWCNTs that reproduced the best absorption spectra, developed a methodology within the LCAO-TDDFT-k-ω framework to obtain optical absorption spectra for heterojunctions. The project also analyzed excitonic density diagrams to assess the charge separation efficiency between holes and electrons in various donor-acceptor combinations. By studying the level alignment, charge transfer, and optical absorption of these complex OPV donor/acceptor systems, we aimed to provide the means to model the optical properties for heterojunctions.

• 第一著者: López Revelo, Yomaira Elizabeth (author)
• フォーマット: bachelorThesis
• 言語: eng
• 出版事項: 2024
• 主題: Teoría del Funcional de Densidad; Clorofila; Nanotubos de carbono de pared simple; Density-functional theory; Chlorophyll; Single-walled carbon nanotubes
• オンライン･アクセス: http://repositorio.yachaytech.edu.ec/handle/123456789/793