Highly Transparent, Highly Thermally Stable Nanocellulose/Polymer Hybrid Substrates for Flexible OLED Devices

Flexible organic light-emitting diode (OLED) devices based on polymer substrates have attracted worldwide attention. However, the current OLED polymer substrates are limited due to weak thermal stability, which is not compatible with the high temperature in OLED fabrication. Here, we developed a novel nanocellulose/polyarylate (PAR) hybrid polymer substrate with both high transparency and excellent thermal properties. Benefiting from the nanometer scale of the cellulose nanofibrils (CNFs) and the efficient interfacial interaction with PAR, the substrate exhibited greatly improved thermal stability, with a glass transition temperature of 192 degrees C, the thermal decomposition temperature of 501 degrees C, and upper operating temperature up to over 220 degrees C. Meanwhile, the hybrid substrate exhibits outstanding mechanical properties. Notably, no apparent transparency loss was observed after the CNF addition, and the hybrid substrate maintains a high transmittance of 85% and a low haze of 1.75%@600 nm. Moreover, OLED devices fabricated on the hybrid substrates exhibit a much improved optoelectrical performance than that of the devices fabricated on the conventional poly(ethylene terephthalate) (PET) substrates. We anticipate this research will open up a new route for fabricating flexible high-performance OLEDs.