Enhancement of Lipid Productivity of Chlorella sp. Using Light-Converting Red Fluorescent Films Based on Aggregation-Induced Emission

The conversion of light wavelength from green (500–600 nm) to red (600–700 nm) in the solar spectrum can significantly enhance the biodiesel productivity of microalgae because microalgal photosynthetic pigments utilize the red light more efficiently. Herein, we applied light-converting fluorescent films to enhance the biomass and lipid productivity of oleaginous Chlorella sp. Although the fluorescent dyes have been reported to exhibit excellent fluorescence quantum yields in the solution state, the solid film state is more preferred to overcome limitations such as low stability and potential leakage issues. However, conventional fluorescent dyes exhibit poor emission in the solid film state due to aggregation-caused quenching (ACQ). Therefore, this study utilized aggregation-induced emission (AIE)-type diketopyrrolopyrrole (DPP) fluorescent dyes to overcome the ACQ problems and to fabricate highly efficient light-converting red fluorescent films. The fabricated light-converting film showed excellent photosynthetic photon flux density increase in the red wavelength range by AIE. A maximum total fatty acid methyl ester increase of Chlorella sp. was 28.8% using a light-converting film containing a deep-red (650–700 nm) emitting dye M2. In conclusion, we confirmed that the use of solar energy with light-converting films could boost microalgal productivity efficiently, even without using light-emitting diodes that require electricity.