Bilayer vertical bulk heterojunction for high-sensitivity conformable organic phototransistors

Conformable organic phototransistors (OPTs) are promising for wearable and biomedical optoelectronics but are limited by insufficient light absorption and inefficient exciton dissociation processes. Here, a bilayer vertical bulk heterojunction (BV-BHJ) is developed via a floating film transfer method using IDT-BT and N2200. The structure integrates vertical phase-separated bulk heterojunctions in both layers with an additional interfacial planar heterojunction, enabling synergistic enhancement of exciton generation, dissociation, and carrier transport. The resulting device exhibits a photosensitivity (P) as high as 1.58 × 10⁶ with excellent mechanical conformability. This work provides an effective strategy for high-performance conformable phototransistors.