Solution-Processed Single-Component Organic Photodetectors - Strong Quadrupole Moments in Molecules Enable the State-of-the-Art Performance

Donor-acceptor based bulk-heterojunctions (BHJ) are commonly used as the photoactive layer in organic photodetectors (OPDs) to utilize the energetic offset formed at the donor and acceptor interface for exciton dissociation. However, this strategy often complicates optimization procedures and raises the concerns over device reproducibility and stability. Herein, we demonstrate that solution-processed single-component organic semiconductors can operate as efficient OPDs. We use non-fullerene acceptors (NFAs) as the single-component photoactive layer, where the intermolecular charge transfer excitonic (CTE) states are formed within <1 ps, and efficient photocurrent generation is achieved via strong quenching of these CTE states by reverse bias. Y6 and IT-4F, prototypical NFAs, based OPDs show excellent OPD performances; low dark current density (~10 -9 A cm -2 ), high responsivity (≥ 0.15 A W -1 ), high specific detectivity (> 10 12 Jones) and fast photo-response time (< 10 μs), comparable to the state-of-the-art BHJ OPDs. We find these excellent single-component NFA OPD performances are strongly correlated with the high quadrupole moments of NFA molecules, which generate the energetic offset required for CTE state separation. Our work opens a new way to realize efficient OPD devices using single-component organic semiconductors via solution processing and provides the important molecular design rules required for single-component photoactive materials.