Highly Transparent, Thermally Stable and Mechanically Robust Hybrid Cellulose-Nanofiber/Polymer Substrates for the Electrodes of Flexible Solar Cells

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 coefficient 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 the excellent compatibility and interfacial interaction with the epoxy matrix, the hybrid substrate’s thermal properties are significantly improved with a decreased CTE of 19ppm/K, increased glass transition temperature (Tg) of 71.8°C, and increased half-life thermal decomposition temperature (Td,50%) of 376 °C. Concurrently, mechanical properties are gre...