Green Fabrication of All-Nanocellulose-Based Flexible Electroluminescent Devices with Biodegradability, Recyclability, and Extreme Environment Tolerance

Flexible electroluminescent (EL) devices have become an important part of lighting and display. However, fabricating a flexible EL device with biodegradability, recyclability, and extreme environment tolerance through a facile and green method still remains challenging to date. Herein, an all-nanocellulose-based flexible EL device with recyclable phosphors is developed by using a sandwich-structured assembly strategy. Biomass-derived cellulose nanocrystals with II crystalline allomorphs (CNCs II) with high transmittance are utilized as a film-forming agent, a dispersant, and an antioxidant for transparent electrodes. Biomass-derived cellulose nanofibers with a high aspect ratio are introduced into the luminescent layer to improve the mechanical stability of the devices. The CNC II-silver nanowire electrodes with high transmittance (81.7%) and low sheet resistance (4.4 Ω sq –1 ) demonstrate conductive stability, damage resistance, and inoxidizability. The assembled EL devices with high luminance (135.7 cd m –2 at 400 V and 20 kHz), tensile strength (16.6 MPa), and mechanical cyclic stability can work properly over a wide temperature range (−20 to 60 °C). With the action of cellulase, the entire device can be completely biodegraded within 7 h. The device prepared with recycled phosphors basically maintains the original mechanical and luminescent properties. The patternable all-nanocellulose-based EL devices with biodegradability, recyclability, and extreme environment tolerance manufactured through an environmentally friendly approach offer a favorable option for future green electronics including wearable devices and flexible display screens.