Spiro-Conjugation in Narrow-Bandgap Nonfullerene Acceptors Enables Broader Spectral Response and Higher Detectivity for Near-Infrared Organic Photodetectors

摘要

Near-infrared (NIR) organic photodetectors (OPDs) are competitive candidatesfor flexible electronics in biomedical imaging and optical communicationsapplications. However, current OPDs still suffer from a low detectivitybeyond 1000 nm and a high dark current at bias due to the lack of highperformancenarrow-bandgap non-fullerene acceptors (NFAs). In this study,spiro-conjugated core donor (D) unit is adopted to construct NFAs, SPT-4Fand tSPT-4F. Comparing with PT-4F without spiro-conjugation, the orthogonalspiro-conjugated planes endow SPT-4F and tSPT-4F with more rigid conformationand thus superior intermolecular stacking, resulting in the enhancedabsorption beyond 1000 nm. Impressively, tSPT-4F based device gives the bestperformance with a dark current of 4.52 × 10~(?1)0 A cm~(?2) under reversed bias of?0.1 V, an external quantum efficiency (EQE) response over 48 at 1010 nm,a detectivity of 1.25 × 10~(13) Jones and a responsibility of 0.40 A W~(?1) at 1010 nm.To the best of the authors’ knowledge, this is one of the best performeddevices reported to date for binary NIR OPDs with response beyond 1000 nm.This study provides a feasible molecular design strategy to develop narrowbandgapNFAs with spiro-conjugation for highly detective NIR OPDs.