Excellent Mechanical Performance of Cellulose Composite Papers for Flexible Self-Powered Photodetectors Using the ZnO/PbS Heterojunction

Cellulose is attracting considerable attention in the field of flexible electronics due to its unique properties and environmental sustainability, particularly as a substrate for flexible devices. Flexible photodetectors are an integral part of cellulose-based devices and have become essential in optical communication, heart rate monitoring, and imaging systems. The performance and adaptability of these photodetectors depend significantly on the quality of the flexible substrates. However, poor bonding with conductive materials results in poor conductivity stability, and limited thermal stability makes cellulose unsuitable for many preparation processes. This study designed polyvinylpyrrolidone (PVP)-coated silver nanowires (AgNWs) as conductive materials, integrating them with cellulose nanofibers (CNFs). The resulting AgNW/CNF composite paper demonstrated high tensile strength (183.9 MPa), low sheet resistance (2.38 Ohm sq^-1), and excellent bending durability. Spin-coated PbS colloidal quantum dots (CQDs) films and low-temperature magnetron-sputtered ZnO films were used as functional layers to create a flexible self-powered photodetector. This device features low dark current density (2.35 × 10^-9 mA cm^-2 @0 V), fast photoresponse (40/24 ms), and stability under bending (up to 180°, 1 mm radius). It shows potential for applications in infrared optical communication and real-time heart rate monitoring, demonstrating the promise of cellulose substrate photodetectors for flexible electronics.