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 °C, the thermal decomposition temperature of 501 °C, and upper operating temperature up to over 220 °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.

For flexible electronics, the substrates play key roles in ensuring their performance. However, most substrates suffer from weak bonding with the conductive ink and need additional aids. Here, inspired by the Ag−S bond theory, a novel cellulose nanopaper substrate is presented to improve the bond strength with the Ag nanoparticle ink through a facile printing method. The substrate is fabricated using thiol-modified nanofibrillated cellulose and exhibits excellent optical properties (∼85%@550 nm), ultra-small surface roughness (3.47 nm), and high thermal dimensional stability (up to at least 90 °C). Most importantly, it can attract Ag nanoparticles initiatively and bind them firmly, which enable the conductive ink to be printed without using the ink binder and form a strong substrate−ink bonding and maintain a stable conductivity of 2 × 10 −4 Ω cm even after extensive peeling and bending. This work may lead to exploring new opportunities to fabricate high-performance flexible electronics using the newly developed nanopaper substrate.

The polymer substrates of flexible solar cell (FSC) electrodes play a crucial role in determining the electrode performance as well as the device performance and reliability. However, most of the FSC electrode polymer substrates suffer from high coefficients of thermal expansion (CTE) and thermal instability when exposed to thermal-cycling impact. Here, a nanocellulose/epoxy hybrid substrate employing chemically modified cellulose nanofibers, demonstrating significantly improved thermal properties as well as high optical transparency, is presented. Benefiting from nanoscale morphology and surface functional groups of the cellulose nanofibers, which enable excellent compatibility and interfacial interaction with the epoxy matrix, the hybrid substrate’s thermal properties are significantly improved with a decreased CTE of 19 ppm/K, increased glass -transition temperature (T g) of 71.8 °C, and increased half-life thermal decomposition temperature (T d,50%) of 376 °C. Concurrently, mechanical properties are greatly enhanced with increases in ultimate strength and ultimate strain by 41 and 121.5%, respectively. In particular, the hybrid substrates maintained their high transmittance of 89%@600 nm and demonstrated no transparency loss after the introduction of cellulose nanofibers. Moreover, the conductive layer of poly­(3,4-ethylene­dioxy­thio­phene):poly­styrene­sulfonate deposited on the substrate retained a stable conductivity of around 835 S/cm without noticeable electrical degradation after withstanding the environmental thermal-cycling impact. With significantly improved thermal and mechanical properties as well as retained optical transparency and stable electrode conductivity, the use of this newly developed hybrid substrate may open opportunities for the fabrication of high-performance, low-cost FSCs.

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