High-Strength, Stable, and Energy-Efficient Bacterial Nanocellulose Composite Films for Building-Integrated Photovoltaics Facade System

Bacterial nanocellulose (BNC) composite films have emerged as promising candidates for sustainable building materials, yet their practical application in building-integrated photovoltaics (BIPV) facade systems is hindered by insufficient mechanical strength, poor environmental stability, and limited energy efficiency. Here, we developed bacterial nanocellulose/zinc oxide–phenolic resin (BNC/ZnO–PF) composite films with high-strength, stability, and energy efficiency for BIPV facade system through a simple strategy. Specifically, we first prepared BNC films, then in-situ grew ZnO nanoparticles on BNC films via ultrasound assistance, and finally hot-pressed the BNC/ZnO films with PF resin. The BNC/–PF composite films exhibit high mechanical strength (tensile strength of 93.8 MPa), exceptional sturdiness (wet strength of 92.3 MPa), and thermal properties, demonstrating their durability for long-term outdoor applications. Furthermore, the BNC/ZnO–PF composite films show high transparency (86.47%) and haze (82.02%) in the visible light range, enabling effective light propagation and scattering, as well as soft, uniform, and large-area light distribution. Meanwhile, a low thermal conductivity of 21.7 mW·m⁻¹·K⁻¹ can effectively impede the transfer of high outdoor temperatures into the room, significantly reducing the energy consumption demands of heating and cooling systems. Coupled with its ability to en-hance the photovoltaic conversion efficiency of solar cells by 12.9%, this material can serve as the core encapsulation layer for BIPV facades. While enabling build-ing-integrated photovoltaic power generation, through the synergistic effect of light management and thermal insulation, it is expected to reduce comprehensive building energy consumption, providing a new solution for building energy efficiency under carbon neutrality goals.