Opportunity
The increasing global energy crisis has highlighted the urgent need for energy-efficient solutions, particularly in building design where conventional glass windows contribute significantly to energy consumption. Traditional glass windows, while offering excellent transparency, suffer from several drawbacks including high weight, fragility, excessive thermal conductivity, and glare. These limitations lead to poor building energy efficiency, unsatisfactory thermal environments, and heightened safety risks. Smart window technologies have emerged as a potential solution, but existing materials like thermochromic perovskites coated on glass or transparent wood face challenges. For instance, transparent wood fabrication often requires delignification, which weakens the wood structure and hinders large-scale production. Meanwhile, thermochromic perovskites deposited on glass inherit the mechanical and thermal drawbacks of glass. There is a pressing need for a composite material that combines the mechanical robustness of wood with the smart solar regulation of perovskites while avoiding the pitfalls of existing technologies.
Technology
This patent addresses these challenges by introducing a novel composite material comprising an optically transparent wood substrate impregnated with a polymer (e.g., PMMA), a thermochromic halide perovskite layer (e.g.,MA4PbI5Br·2H2O ), and a protective polymer layer (e.g., PMMA). The innovation lies in:
1. Lignin Modification Without Delignification: The wood substrate undergoes UV-assisted bleaching to deactivate lignin chromophores without removing lignin, preserving mechanical strength while achieving transparency.
2. Polymer Impregnation: A refractive index-matched polymer (e.g., PMMA) infiltrates the wood’s cellular structure, enhancing optical clarity and mechanical properties.
3. Thermochromic Perovskite Layer: A spin-coated halide perovskite layer enables reversible solar modulation (21–78% luminous transmittance) with a transition temperature of ~44.5°C and rapid response (~102 seconds).
4. Protective Layer: A hydrophobic polymer coating (e.g., PMMA) shields the perovskite from moisture degradation, maintaining 94% solar modulation ability after 50 cycles.
Advantages
- Energy Efficiency: Solar modulation ability of 21.6% reduces cooling loads in buildings.
- Mechanical Robustness: Tensile strength of 56 MPa and flexural strength of 93 MPa surpass traditional glass.
- Thermal Insulation: Low thermal conductivity (0.24 W/(m·K)) compared to glass (1–1.4 W/(m·K)).
- Optical Performance: High optical haze (~90%) for privacy and diffuse lighting; maintains 78% transmittance in cold states.
- Durability: PMMA protective layer ensures stability against humidity and cycling degradation.
Applications
- Smart Windows: For energy-efficient buildings with passive solar regulation.
- Thermal Management Systems: In greenhouses or skylights to modulate heat gain/loss.
- Privacy Glass: High haze properties suit offices/residential spaces requiring light diffusion.
- Sustainable Construction: Lightweight alternative to glass with lower embodied energy due to wood-based substrate.
