Molecular engineering and structure–property relationship based on D–A chlorophyll derivative and the application in organic solar cells

Abstract

The photoactive layer materials of organic solar cells (OSCs) play a critical role in achieving excellent performance. Chlorophyll derivatives are commonly used due to their environmental friendliness, low cost, and easy accessibility. However, the efficiency of OSCs based on chlorophyll is limited by their photoelectric properties. Here, we focused on the D–A structure of chlorophyll derivative ZnChl-1 and designed four molecules through rational molecular engineering. The photoelectric properties at the microscopic level were systematically studied using density functional theory (DFT). Our findings reveal that T-ZnChl-1 with triphenylamine donor unit has a smaller energy gap and ionization energy, as well as a larger spectral red shift and absorption range. This suggests that intramolecular charge transfer will be enhanced, leading to an improvement in short-circuit current. Furthermore, Y6 is used as the acceptor to construct the heterojunction interfaces. The results indicate that the T-ZnChl-1/Y6 interface exhibits more charge transfer states and higher exciton dissociation rate K_CS, which will promote charge separation and lead to excellent photovoltaic performance. This work clarifies the structure–property relationship of chlorophyll derivatives and the photo-response mechanism of intermolecular charge transfer, providing a theoretical basis for developing valuable chlorophyll-based OSCs.