Whats special about Y6; the working mechanism of neat Y6 organic solar cell

Non-fullerene acceptors (NFA) have delivered advance in bulk heterojunction organic solar cell efficiencies, with the 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 neat Y6 device with 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 Y6 generates bulk free charges, with ambipolar mobility, which can be extracted in the presence of transport layers