Flexible Self-Powered Organic Photodetector with High Detectivity for Continuous On-Plant Sensing

Abstract

Organic photodetectors (OPDs) exhibit performance on par with inorganic detectors (e.g., Si) but can be ultrathin, ultra-lightweight, flexible, and mechanically resilient, opening up opportunities for novel applications including optical sensors for continuous human and plant health monitoring. Here, a high-performance flexible self-powered OPD designed for on-plant optical sensing is developed. The OPD employs an electrode consisting of Ag nanowires (NWs) embedded in a UV-curable resin to achieve a flexible and thin form factor. In addition, the OPD active layer consisting of D18-Cl and Y6 is sequentially cast to reduce dark current. The flexible OPD is sensitive to 400–950 nm wavelengths and exhibits photodetector characteristics comparable to state-of-the-art rigid OPDs. The responsivity reaches values of 0.47 A W−1 and specific detectivity exceeds 1012 Jones. Owing to the embedded Ag NW electrodes in a thin substrate (t = 20 µm) and sequentially cast active layers, the detector demonstrates excellent bending stability. The photocurrent remains steady across 4000 cycles with a bending radius of 2 mm. The flexible OPD is demonstrated to effectively detect plant uptake of the rare-earth metal terbium and sense time-dependent chlorophyll fluorescence. Thus, this work highlights the potential for OPDs as on-plant sensors to advance precision agriculture.