Layer-by-layer assembly of 1-D photonic crystal for wavelength-selective optical filter

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Solar greenhouse technology that efficiently utilizes solar energy by splitting the full solar spectrum for plant cultivation and electricity generation using solar cells is a promising strategy for realizing sustainable agriculture. A one-dimensional photonic crystal (1-D PC) that selectively transmits the red and blue lights for photosynthesis, but reflects the other wavelengths is a key component of solar cells. However, the industrial production of 1-D PC thin films is limited due to high production costs of the typically employed gas-phase deposition methods. Here, we demonstrated the fabrication of a 1-D PC thin film for wavelength-selective reflection and transmission using a spray-coating-based layer-by-layer assembly method. The reflected wavelength can be finely tuned by controlling the SiO2 layer thickness using different numbers of spraying cycles. In addition, increasing the number of stacked layers can significantly improve the reflection intensity. The fabricated 1-D PC thin film exhibited a high selective transmittance of 77% and 87% at 450 (blue) and 660 nm (red) together with a reflectance of 69% at 550 nm (green). This work provides a cost-effective solution-based process for preparing 1D PC thin films and provides significant insights into developing solar greenhouse technology.