Quasi-Steady-State Measurement of Exciton Diffusion Lengths in Organic Semiconductors

Understanding exciton diffusion in organic solar cells is crucial to understanding the recent rise in power-conversion efficiencies afforded by using non-fullerene acceptor molecules (NFAs). This study introduces a technique called pulsed-PLQY for measuring exciton diffusion lengths in organic semiconductors. Compared to existing techniques, pulsed-PLQY is faster, easier, requires less specialized equipment, and is less sensitive to experimental conditions. Using this method, the authors find that modern non-fullerene acceptor semiconductors exhibit longer diffusion lengths than their fullerene forerunners, and that this increase is driven by increases in diffusivity.