An efficient strategy for designing high-performance DSSCs: Using the terminal auxiliary acceptor to improve electronic transitions

Introducing electron-withdrawing groups and adding co-sensitizers into dye sensitizers are considered feasible strategies to improve the energy conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). However, the mechanisms by which these two strategies affect photovoltaic properties are not fully understood. In this paper, five photosensitizers were synthesized through simple steps. Based on ZS09, four A′–π–A dyes were constructed using electron-deficient pyrazine derivatives. The PCE evaluation value of ZS10-based DSSC is 5.28%, about 16% higher than that of ZS09-based DSSC. Undoubtedly, this dramatic improvement should be attributed to the role of auxiliary acceptors, which effectively facilitate the ICT transition by increasing the overlap of the frontier molecular orbitals, leading to an increase in light-harvesting efficiency. Furthermore, the co-sensitization of YD2 and ZS12 on the TiO2 photoanode achieved the best photovoltaic efficiency of 7.13%. With the help of the quantum chemical calculation method and experimental results, this study reveals the effects of auxiliary acceptors on electron distribution, excited state properties, and photovoltaic performance, which provides a new idea for designing high-performance DSSCs in the future.