Ambipolar charge transport in a non-fullerene acceptor

Charge transport is one of the key factors in the operation of organic solar cells. Here, we investigate the electron and hole transport in the non-fullerene acceptor (NFA) IT-4F, by a combination of space-charge-limited current measurements and multiscale molecular simulations. The electron and hole mobilities are fairly balanced, amounting to 2.9 x 10(-4) cm(2) V-1 s(-1) for electrons and 2.0 x 10(-5) cm(2) V-1 s(-1) for holes. Orientational ordering and electronic couplings facilitate a better charge-percolating network for electrons than for holes, while ambipolarity itself is due to sufficiently high electron affinity and low ionization energy typical for narrow-gap NFAs. Our findings provide a molecular-level understanding of the balanced hole and electron transport in an archetypical NFA, which may play a key role in exciton diffusion and photogenerated hole transfer in organic solar cells.

Automated summary

In this study, the electron and hole transport in the non-fullerene acceptor (NFA) IT-4F were investigated using space-charge-limited current measurements and multiscale molecular simulations. The electron and hole mobilities were found to be fairly balanced, with values of 2.9 x 10(-4) cm(2) V-1 s(-1) for electrons and 2.0 x 10(-5) cm(2) V-1 s(-1) for holes. The balanced transport is attributed to the narrow energy gap and high electron affinity of the NFA, which facilitate a better charge-percolating network for electrons than for holes. These findings provide insights into exciton diffusion and photogenerated hole transfer in organic solar cells.