Highly Stretchable Transparent Electrodes for Wearable Near-Infrared Organic Photodetectors Enabling Vital Monitoring, Imaging, and Communication.

Abstract

Stretchable near-infrared organic photodetectors (NIR OPDs) are crucial for the development of wearable and implantable electronics. However, these devices commonly underperform compared to their rigid counterparts, primarily due to the lack of high-quality stretchable transparent electrodes. Here, we develop silver nanowires (AgNWs)/thermoplastic polyurethane (TPU) composite electrodes by introducing 3-[N-tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic acid sodium salt (HOS). The resulting AgNWs-HOS/TPU electrodes show impressive optical transmittance and low sheet resistance (12 Ω·sq^-1), comparable to ITO/glass electrodes. Notably, the incorporation of HOS significantly improves the adhesion between AgNWs and TPU, ensuring a low sheet resistance (21.3 Ω·sq^-1) even under mechanical deformation of 80%. Consequently, the AgNWs-HOS/TPU-based stretchable OPDs exhibit a record-high shot-noise-limited specific detectivity (D*_shot) of 5.58 × 10¹³ Jones at 800 nm, comparable to rigid devices. Moreover, these stretchable devices maintain a D*_shot > 10¹³ Jones after 500 stretching cycles at 50% strain and sustain a D*_shot over 10¹³ Jones under continuous stretching at 30% strain for over 80 min, ranking as the highest value among stretchable OPDs in photovoltaic mode reported so far. Furthermore, the stretchable NIR OPDs are successfully applied in pulse signal detection, imaging, and optical communication, and they are capable of accurate signal detection after cyclic stretching, which demonstrates great potential in wearable and implantable devices.