Revolutionizing Quinoidal Optoelectronics Through Heterojunction Engineering for Tri-Modal Reconfigurability...

Quinoidal-conjugated materials are notable for their ultra-low LUMO levels (<-4.0 eV) and exceptional wide-spectral absorption in the NIR-II region, attributed to their narrow optical bandgaps. However, their inferior charge transport properties hinder the simultaneous optimization of light absorption and carrier mobility, thereby limiting performance in detection sensitivity and response speed across the UV-vis-NIR range. To address this challenge, we developed a novel heterojunction architecture phototransistor combining a new n-type quinoidal small molecule (Q4T) with a p-type organic semiconductor (C10-DNTT). Leveraging the complementary absorption of heterogeneous semiconductors and efficient intermolecular charge transfer in type-II heterojunctions, the phototransistor enables wide-spectral detection from 300 to 1200 nm. It demonstrates tri-modal operational reconfigurability, offering versatile photoresponse characteristics. Remarkably, the device exhibits a low detection threshold of 3 µW cm^-2, underscoring its high sensitivity. Additionally, the optimized heterostructure ensures a fast response time of 20 ms, making it a promising candidate for high-performance optoelectronic applications. The integration of spectrally resolved positive/negative photoconductivity with gate-tunable operation modes enables high-contrast image sensing and secure information encryption/decryption. This heterojunction strategy effectively addresses the inherent limitations of quinoidal semiconductors and establishes a versatile platform for all-organic bidirectional optoelectronic systems, offering promising prospects for intelligent spectral sensing technologies.