Synthesis and characterization of Y6-derived non-fullerene acceptors for organic photovoltaics

Abstract

Organic photovoltaics (OPVs) has been a promising development to phase out non-renewable fossil fuels. Fullerene-derivatives were employed in the earliest OPVs for their excellent electron mobility. However, their high cost, poor tunability and poor solubility have limited further development. In 2019, a revolutionary non-fullerene acceptor (NFA) Y6 was reported with a power conversion efficiency (PCE) of almost 16%. Since then, a lot of research has been conducted to understand the superior performance of Y6-based devices and to design novel Y6-derived NFAs with improved performance. In Chapter 2, the effect of incorporating alkylthio side chains onto a Y6 core was investigated for the first time. The best NFA in our study was BTPS-4F, with a PCE of up to 16.2%. The study demonstrated that incorporating alkylthio side chains is a viable strategy to tune the energy levels and morphology of Y6-derived NFAs. This work has provided valuable experience to further studies on the device optimization and exciton dynamics of alkylthio-containing NFAs. In Chapter 3, we synthesized and examined the FCl-IC end group. We showed that applying FCI-IC is an effective and environmentally friendly method to precisely control the optoelectronic properties and morphology. It was also possible to dissolve the NFA, Y6BO-2(FCl), in xylene during device fabrication. The best PCE achieved was 12.7%. With further optimizations, we are confident that this sustainable strategy will be essential in the large-scale application of OPVs.

Date of Award	2021
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	He YAN (Supervisor)