带有噻吩侧基的有机硼小分子电子受体光伏材料

有机小分子电子受体材料的侧基能够影响异质结有机太阳能电池的给体/受体匹配和器件性能。我们设计并合成了一个硼原子带有噻吩侧基的有机硼小分子(MBN-Th)。该分子的LUMO离域在整个骨架上,HOMO定域在中心核上,其独特的电子结构使该分子具有两个强的吸收峰(波长分别为490和726nm),因此分子具有宽的吸收光谱和强的太阳光吸收能力。与苯基侧基相比,噻吩侧基使分子的HOMO能级下移0.1 eV,LUMO能级保持不变,进而引起分子带隙减小和吸收光谱蓝移20nm。基于该有机硼小分子受体材料的异质结有机太阳能电池,实现了4.21%的能量转化效率和300–850nm的宽响应光谱。实验结果表明,硼原子上的噻吩侧基是调控有机硼小分子光电性质的有效方法,可以用于有机硼小分子受体材料的设计。

An Organoboron Compound with a Thienyl Substituent as an Electron Acceptor for Organic Solar Cells

Recently, non-fullerene small molecular acceptors (NFSMAs) have received great attention because of their broad and strong absorption spectra and stable active layer morphology when compared with traditional fullerene acceptors. The most widely used strategy to design NFSMAs is through A-D-A type molecules, in which an electron-rich core unit (D) is flanked by two electron-deficient units (A). In order to fine-tune the absorption spectra, energy levels, and photovoltaic properties of NFSMAs, great efforts have been made to modify the conjugated backbone of A-D-A type molecule acceptors. In a previous work, we developed a small molecular electron acceptor, namely MBN-Ph, with an A-D-A structure and an organoboron core unit. MBN-Ph exhibited distinctive absorption spectra with two absorption bands in short- and long-wavelength regions. It is known that side chains or substituents on small molecular electron acceptors can also play an important role in the molecular properties and photovoltaic performance of bulk heterojunction organic solar cells (OSCs). In this work, we report an A-D-A type organoboron compound (MBN-Th) bearing a thienyl substituent on the boron atom, which can be used as an electron acceptor for OSCs. The lowest unoccupied molecular orbital (LUMO) of MBN-Th delocalized on the entire backbone, while the highest occupied molecular orbital (HOMO) localized on the core unit. The unique electronic structure of MBN-Th resulted in two strong absorption peaks at 490 and 726 nm, which indicate a wide absorption spectrum and superior sunlight harvesting capability. Compared with the phenyl substituent, the thienyl group led to an unchanged LUMO energy level, low-lying HOMO energy level by 0.1 eV, and blue-shifted absorption spectrum by 20 nm. OSCs with MBN-Th as an electron acceptor showed a power conversion efficiency of 4.21% and a wide photoresponse from 300 to 850 nm. Our results indicate that the substitution of the boron atom with a thienyl group is an effective strategy to tune the electronic structure of organoboron compounds for applications as electron acceptors in OSCs.