Electronic and optical properties of CS and CSSe molecules and crystals

• Published in: New journal of chemistry 2022-07, Vol.46 (28), p.13513-13518
• Main Authors: Kuklin, Artem V, Saykova, Diana I, Suresh, Rahul, Begunovich, Lyudmila V, Baryshnikov, Gleb V, Karaush-Karmazin, Nataliya, Saikova, Svetlana V, Ågren, Hans
• Format: Article
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d2nj02539f

Hetero[8]circulenes have been proposed as promising fluorescent emitters for organic light-emitting diodes and as emerging materials in the construction of organic solar cells. Among them, octathio[8]circulene (C 16 S 8 ) and its derivative tetrathiotetraseleno[8]circulene (C 16 S 4 Se 4 ) crystals have been highlighted as efficient charge transport materials in field-effect devices. Using density functional theory, we investigate in this paper the electronic and optical properties of the C 16 S 8 and C 16 S 4 Se 4 molecules and crystals in order to revise previously reported controversial experimental data and report highly reproducible new results. We find that formation of the crystals results in a significant band gap decrease (∼0.6-0.7 eV) caused by relatively strong intermolecular interactions. A partial replacement of S atoms with Se atoms also leads to a small band gap reduction. The C 16 S 8 crystal demonstrates a band gap of 3.32 eV, while a band gap of 3.20 eV is found for C 16 S 4 Se 4 . Both C 16 S 8 and C 16 S 4 Se 4 compounds are optically transparent in the visible region, confirming the absence of red coloration reported previously in one of experimental papers. The C 16 S 8 and C 16 S 4 Se 4 crystals demonstrate anisotropic electronic, mechanical and optical properties. These findings might initiate future experimental studies of the red color origin for C 16 S 8 and provide insight for the design and engineering of C 16 S 8 and C 16 S 4 Se 4 based charge transport and optical devices. Here we report electronic and optical properties of C 16 S 8 and C 16 S 4 Se 4 molecules and crystals and resolve previously reported experimental inconsistencies.