Star-Shaped Molecules with a Triazine Core: (TD)DFT Investigation of Charge Transfer and Photovoltaic Properties of Organic Solar Cells

• Published in: Brazilian journal of physics Vol. 54; no. 6
• Main Authors: Rosa, Nathália M. P., Borges, Itamar
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-12-2024; Springer Nature B.V
• Subjects: Bulk density; Carbazoles; Charge transfer; Computation; Density functional theory; Dye-sensitized solar cells; Dyes; Electronic structure; Emitters; Energy conversion efficiency; Energy levels; Heterojunctions; Open circuit voltage; Optoelectronics; Organic light emitting diodes; Physics; Physics and Astronomy; Photovoltaic properties and charge transfer; Dye-sensitized solar cells; Star-shaped molecules; Triazine core; Time-dependent density functional theory (TD-DFT); Bulk heterojunction organic solar cells; Density functional theory (DFT)
• ISSN: 0103-9733; 1678-4448
• DOI: 10.1007/s13538-024-01636-2

We investigate theoretically the design and application of nine triazine (Tr)-core star-shaped molecules built with thiophene (Th), phenyl (Ph), and carbazole (Cz) moieties in dye-sensitized solar cells (DSSCs) and bulk heterojunction (BHJ) organic solar cells. Density functional theory and time-dependent density functional theory are employed to rationalize the electronic structure, charge transfer properties, and photovoltaic performance of these systems. Tr-Th-Cz and Tr-Ph-
p
-Th-Cz display power conversion efficiency (
PCE
) values close to 30% due to a favorable alignment of the energy levels. Computed open-circuit voltage values show that lack of π-bridges, as in the Tr-Th and Tr-Cz, favor higher voltage generation. Systems containing thiophene (Th) and carbazole (Cz) present the most favorable values for efficient electron injection and dye regeneration. Furthermore, the incorporation of these Th and Cz donor substituents into the triazine core combined with π-bridges significantly impacts other optoelectronic properties of the organic solar cells. The computed high singlet–triplet gap values indicate limited potential of these molecules as thermally activated delayed fluorescence (TADF) emitters for applications in organic light-emitting diodes (OLEDs).