Individually Tunable Energy Levels of Oligomers Based on N−B←N Units

• Published in: Angewandte Chemie International Edition 2024-12, Vol.63 (49), p.e202411023-n/a
• Main Authors: Zhu, Xiaoyu, Zhang, Yingze, Miao, Junhui, Liu, Jun, Wang, Lixiang
• Format: Article
• Language: English
• Subjects: Atomic energy levels; Charge transfer; Electronic equipment; Energy charge; Energy levels; Excitation; Molecular orbitals; monodisperse oligomers; Oligomers; organic photodetectors; Organic semiconductors; Triplet state
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202411023

Opto‐electronic properties and device performance of organic semiconductors are mainly determined by energy levels of their frontier molecular orbitals, e.g. lowest unoccupied molecular orbital (ELUMO) and highest occupied molecular orbital (EHOMO) in the ground state, first singlet state (ES1) and first triplet state (ET1) in the excited state. These energy levels are always intricately intertwined. Herein, we report a series of monodisperse oligomers based on double B←N bridged bipyridine (BNBP) units. With the increasing number of repeating units, the oligomers exhibit gradually downshifted ELUMO and nearly unchanged EHOMO due to the different distribution of the frontier molecular orbitals of the oligomers. Moreover, the oligomers exhibit gradually decreasing ES1 and nearly unchanged ET1 because of the different contributions of the charge transfer component in the excited state. This work provides new insight into energy level tuning of organic semiconductors, which is important for high‐performance organic opto‐electronic devices. A series of monodisperse oligomers based on electron‐accepting double B←N bridged bipyridine (BNBP) unit with individually tunable energy levels were developed. This unique energy level tuning is attributed to the separation of LUMO and HOMO at the atomic scale of the BNBP unit and the different contributions of charge transfer transitions in the excited states.