Key Molecular Perspectives for High-Performance Non-Fullerene Acceptor Organic Photovoltaics and Photodetectors
Ji-Seon Kim a
a Department of Physics & Centre for Processable Electronics, Imperial College London, UK
Invited Speaker, Ji-Seon Kim, presentation 058
Publication date: 24th October 2023

Organic photovoltaic (OPV) and photodetector (OPD) devices are attracting significant attention due to their potential to be lightweight, flexible, non-toxic, and compatible with large-scale manufacturing. In particular, the development of the new small molecule-based non-fullerene acceptors (NFAs) has enabled OPVs to show remarkable improvements in device efficiency. Although promising, there is still a lack of clear understanding of the impact of molecular structure and orientation of NFAs on photophysical processes critical for device performance. 

In this talk, I will discuss the two key NFA molecular perspectives for high performance OPV and OPD devices.  First, I will show the molecular-structure dependent photostability, with a particular focus on NFA molecular planarity, rigidity, and end groups [1, 2]. Second, I will show the molecular orientation-dependent energetic shifts in NFAs, demonstrating the impact of NFA quadruple moments and molecular orientation on material energetics and thereby on the OPV and OPD performances [3, 4]. Compared to sublimed small molecules where the molecular orientation control is relatively easy [5], there has been no report, to the best of our knowledge, demonstrating the orientation control of solution-processed NFA molecules leading to an energetic shift large enough to impact exciton separation for free charge generation. As such, it is now critical to understand the molecular origins of OPV/OPD performance in much deeper detail than before to direct synthesis of organic semiconductors in more promising directions.

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