Interface-Driven Bipolar Photoresponse in a Doping-Engineered n-Type Polymer Enables Single-Layer Retinomorphic Devices.

Abstract

Retinomorphic hardware, inspired by the human visual system, integrates sensing and preprocessing within the same device and requires optoelectronic pixels capable of electrically encoding photoresponse into antagonistic ON and OFF pathways. Existing approaches generally rely on gated architecture or high-voltage polarization switching (typically >1 V), which increases circuit complexity and dynamic power consumption for device reconfiguration. Here, we report a vertical two-terminal organic optoelectronic design based on a single-layered-doped conducting polymer, n-doped poly(benzodifurandione) (<i>n</i>-PBDF), with asymmetric electrodes. Leveraging electrode asymmetric work function and polymer doping engineering, the proposed device achieves continuous analog tuning of photoresponse polarity from negative to positive at low operational voltage (<0.2 V), enabling the emulation of antagonistic visual encoding. The <i>n</i>-PBDF-based device also exhibits robust reversible negative-to-positive photoresponse switching for 10⁶ cycles and stable retention for 78 days under ambient conditions. These characteristics, together with its structurally compact pixel, enable crossbar array-level in-sensor image processing, including edge enhancement and trainable image classification. The results establish a compact organic hardware primitive for low-voltage, reconfigurable, retina-inspired vision systems.