  Understanding the role that exciton diffusion plays in organic solar cells is
a crucial to understanding the recent rise in power conversion effciencies
brought about by non-fullerene acceptors (NFA). Established methods for
measuring exciton diffusion lengths in organic solar cells require specialized
equipment designed for measuring high-resolution time-resolved
photoluminescence (TRPL). Here we introduce a technique, coined pulsed-PLQY, to
measure the diffusion length of organic solar cells without any temporal
measurements. Using a Monte-Carlo model we simulate the dynamics within a thin
film semiconductor and analyse the results using both pulsed-PLQY and TRPL
methods. We find that pulsed-PLQY has a larger operational region and depends
less on the excitation fuence than the TRPL approach. We validate these
simulated results by preforming both measurements on organic thin films and
reproduce the predicted trends. Pulsed-PLQY is then used to evaluate the
diffusion length in a variety of technologically relevant organic
semiconductors. It is found that the diffusion lengths in NFA's are much larger
than in the benchmark fullerene and that this increase is driven by an increase
in diffusivity.
