2022 ACS Applied Materials & Interfaces, How to Modify Non-Fullerene Acceptors to Improve the Performance of Organic Solar Cells

Enlitech’s REPS and FTPS systems make Voc-oss analysis of solar cells no longer out of reach!

　　UNIST Changduk Yang of South Korea and Seung Man Noh of the Korea Research Institute of Chemical Technology recently published a study in ACS Applied Materials & Interfaces. Non-fullerene acceptors are suitable for high-performance organic solar cells (OSCs) due to their good photoelectric and morphological tunability. Modification of the end-capping groups in non-fullerene acceptors (NFAs) is an effective strategy to modulate their properties and the overall NFAs. In this study, we report the synthesis of a novel γ-ester-functionalized IC end-capping group (IC-γe) and its incorporation into the benzothiadiazole-fused central core to produce isomer-free IC-γe end-capped NFAs, such as Y-IC-γe, Y-FIC-γe, and Y-ClIC-γe. The resulting NFAs exhibit similar absorption profiles, but with an upward shift in the lowest unoccupied molecular orbital energy level compared to those of the ester-free analogues, such as Y6 and Y7.

　　Experiments were carried out through Enlitech’s FTPS Fourier transform photocurrent spectroscopy system, REPS photovoltaic Voc-loss analyzer and other instruments. The results showed that:

Without thermal annealing, the annealing-free OSC based on Y-FIC-γe with the PM6 donor polymer achieved an excellent power conversion efficiency (PCE) of 16.4%, which exceeded the OSCs based on Y-IC-γe and Y-ClIC-γe.
Compared with the symmetric Y-IC-γe case, the OSCs based on asymmetric Y-FIC-γe and Y-ClIC-γe have higher thermal stability, with a PCE retention rate of over 83% after 456 h at high temperature.

　　In this study, we not only established the structure-property relationship regarding the ester functionality and symmetricity tuning on the NFAs, but also diagnose the reasons for the best-performance OSCs based on Y-FIC-γe, which provides useful information for a novel high-performance NFA design strategy.