High transmittance, high haze, and UV-harvesting CNNs@CNF/PVA composite film for light management

Translucent materials are widely used in indoor lighting, electronic display devices, photovoltaic devices, and other aspects of daily life. Developing materials with high transparency that can effectively manage the transmitted light spectrum is of significant practical importance. This study focuses on constructing a flexible composite film matrix using biomass nanocellulose fibrils (CNF) and polyvinyl alcohol (PVA) as raw materials. Based on the down-conversion luminescence principle, we use carbon nitride nanosheets (CNNs) as the core for light management, filtering UV rays from sunlight while converting them into visible light for light compensation. The transparency test results show that the prepared CNNs@CNF/PVA flexible composite film has a total transmittance of about 90% in the visible light range, with a haze greater than 60%. Three-dimensional fluorescence test results indicate that CNNs@CNF/PVA can convert UV light in the range of 250–375 nm into visible light in the range of 420–550 nm. Simulated outdoor lighting results show that the composite film material performs better than ordinary glass and PMMA in light transmission. This biomass-based flexible film material is expected to have broad applications in indoor lighting, flexible photovoltaic devices, and high-quality fruit and vegetable cultivation.