The emergence of the Y series small molecule semiconductors, Y6 and its derivatives, have significantly improved the performance of polymer solar cells (PSCs). However, the excited-state properties of these Y-series small molecule semiconductors which are highly important for designing high-performance PSCs, need to be illustrated. In this work, the excited-state properties and electronic structures of the Y-series small molecules (Y5, Y6, Y10, N3, Y6-BO-4F, and Y6-BO-4Cl) have been systematically studied by using steady-state and time-resolved spectroscopies and quantum chemical calculations. It is shown that the influence of alkyl chains at the nitrogen atom of the pyrrole ring is weak for the electron affinities, ionization potentials, electron and hole reorganization energies and singlet exciton lifetime of Y molecules. Meanwhile, these parameters are found to be varied with the types of electron-deficient termini. Moreover, we find that Y10 and Y5 have the shortest singlet exciton lifetime in solution and the longest singlet exciton lifetime in film (~1100 ps), suggesting the engineering of electron-deficient termini can significantly influence the excited-state lifetime in solution and film. Our work could provide a guideline for designing Y-series acceptor materials for high-performance polymer solar cells.

Y系列小分子半导体Y6及其衍生物的出现大大改善了聚合物太阳能电池（PSC）的性能。但是，这些Y系列小分子半导体的激发态特性对于设计高性能PSC非常重要。在这项工作中，已通过使用稳态系统研究了Y系列小分子（Y5，Y6，Y10，N3，Y6-BO-4F和Y6-BO-4Cl）的激发态性质和电子结构。以及时间分辨光谱学和量子化学计算。结果表明，对于Y分子的电子亲和力，电离势，电子和空穴重组能以及单重态激子寿命，吡咯环氮原子上烷基链的影响较弱。同时，发现这些参数随缺电子末端的类型而变化。此外，我们发现Y10和Y5在溶液中具有最短的单重态激子寿命，在薄膜中具有最长的单重态激子寿命（〜1100 ps），这表明缺电子端基的工程化可以显着影响溶液和薄膜的激发态寿命。 。我们的工作可以为设计用于高性能聚合物太阳能电池的Y系列受体材料提供指导。