Intramolecular nitrogen-sulfur interaction to enhance electron-accepting properties of end groups in small molecule donors

In organic solar cells (OSCs), it is very important to investigate the relationship between the structure and performance of materials by rational design of small molecule donors (SMDs). In this work, we use thiazole replace a thiophene unit in the π bridge, which could strengthen the connection between π bridges and end groups (EGs). Due to the N–S non-covalent interaction between EG and thiazole unit, the negative charge region of SMDs is expanded, the electron-withdrawing ability of EGs is also enhanced, and the corresponding molecular framework is twisted into a unique linear type. This can effectively enhance intermolecular interaction, promote molecular crystallization, and help to improve hole mobility of related SMDs. This work enriches design strategy that strengthens the interaction between π bridges and EGs, and provides a reference for studying the relationship between molecular structure and crystallinity.