The Role of Non-Fullerene Acceptors in Polymer Solar Cells
Posted on Wed, Oct 16, 2019 by Hunan Yi
A great deal of focus has been given to non-fullerene acceptors (NFAs) in recent years, primarily around the research and development of bulk-heterojunction organic solar cells (OSCs). To a large extent they have taken the spotlight in this area away from fullerene derivatives like Phenyl-C81-Butyric Acid Methyl Esters (PCBMs).
PCBMs and other fullerene derivatives
Historically speaking PCBMs and other fullerene derivatives have been the most widely used electron acceptors in organic photovoltaic (OPV) cells.
Unfortunately, although they out-perform most non-fullerene alternatives, fullerene derivates have some significant shortcomings that limit their performance in photovoltaic applications. These include weak light absorption, limited variability of electronic properties, and morphology instability.
As a result of these drawbacks it has proven difficult to obtain high power conversion efficiencies (PCEs) using these materials.
The discovery of ITIC
It was the discovery of the ITIC molecule in 2015 that brought about the first serious challenge to the role of fullerenes as acceptors in polymer solar cells.
With a greater degree of flexibility to tune the optical properties and electronic energy levels, ITIC based organic solar cells offer greater thermal stability and photochemical stability. In addition, they boast longer device lifetimes and higher power conversion efficiencies.
Non-fullerene acceptors take centre stage
Since 2015, interest in non-fullerene based OPV cells has grown rapidly. With efficiencies of over 17% now being achieved, the performance of such devices has overtaken that of their fullerene-based cousins.
As research gathers pace, the first OPV cells with efficiencies in excess of 20% could be on the horizon. This would represent a significant break-through and has only recently become a realistic prospect. Given the progress that has been made in the last four years, there is every reason to be excited about the future of this field.
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Author: Hunan Yi
Hunan is Ossila’s organic chemist, specialising in polymers and functional materials synthesis, polymeric semiconductors, and purification of conjugated polymers. Having achieved an MSc from Shanghai China, Hunan moved to St Andrews University to study towards his PhD in Dye-Sensitised Solar Cells where he then remained as Research Fellow until 2004. He then became a Postdoctoral Research Associate at the University of Sheffield, before working with both the University and Ossila as a KTA associate in 2015.