What is special about Y6; the working mechanism of neat Y6 organic solar cells

Non-fullerene acceptors (NFAs) have delivered advancement in bulk heterojunction organic solar cell efficiencies, with a significant milestone of 20% now in sight. However, these materials challenge the accepted wisdom of how organic solar cells work. In this work we present a neat Y6 device with an efficiency above 4.5%. We thoroughly investigate mechanisms of charge generation and recombination as well as transport in order to understand what is special about Y6. Our data suggest that Y6 generates bulk free charges, with ambipolar mobility, which can be extracted in the presence of transport layers.

Automated summary

Non-fullerene acceptors (NFAs) have significantly increased the efficiency of bulk heterojunction organic solar cells, with a potential milestone of 20% approaching. However, the mechanisms of how these materials function challenge the conventional understanding of organic solar cells. This study presents a Y6 device with an efficiency over 4.5% and investigates the generation, recombination, and transport of charges to understand the unique properties of Y6. The data suggests that Y6 generates abundant bulk free charges with ambipolar mobility that can be extracted when transport layers are present.