Triphenylamine moieties substituted diketopyrrolopyrrole derivatives showed highly emissive characteristics in solid film state by 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.

Herein, we report significant fluorescence quenching induced by intramolecular photoinduced electron transfer (PET) in electron donor−acceptor-type π-conjugated organic molecules with methoxy-containing donor moieties. The fluorescence quenching of the diketopyrrolopyrrole (DPP, a well-known highly emissive luminophore) derivatives seemed to be affected by the methoxy moieties. Steady-state optical properties of the synthesized materials were analyzed in the solution, aggregate (N-methyl-2-pyrrolidone/H 2 O), and solid states in order to understand the influence of the surrounding environment. The mechanistic aspect of the intramolecular PET process in methoxy-containing DPP derivatives was revealed by singlet oxygen generation measurements and ultrafast femtosecond transient absorption spectroscopy. These results could provide crucial insights toward designing emissive π-conjugated organic molecules.

Recently, semitransparent luminescent solar concentrators (LSCs) have attracted considerable attention because they offer an easy and cost-effective route to harvest incident light. Various fluorophores including semiconducting quantum dots and organic dyes have been prepared and utilized for LSC fabrication. However, the narrow light absorption range, reabsorption losses, and limited photostability of the fluorophores still hinder the widespread use of LSCs under outdoor and indoor light conditions. Here, we rationally designed an LSC utilizing aggregation-induced emissive fluorophores (AIEgens) and an energy transfer (ET) strategy. We employ diketopyrrolopyrrole with triphenylamine moiety as a highly stable AIEgen that functions as an emissive ET acceptor in LSC; for a donor, we use tetraphenylethene containing triphenylamine moiety that shows good aggregation-induced emission features and excellent spectral overlap with the acceptor to yield an efficient ET process. A thin-film LSC device with an optimized donor:acceptor ratio (1:0.5) was fabricated. Under AM 1.5G solar spectrum, an LSC coupled with three side reflectors and a backside diffuser exhibits 18% optical conversion efficiency and a concentration factor of 1.18. Under indoor white LED illumination, the values were 27% and 1.68%, respectively. After exposed to intense UV radiations for 5 hours, the LSCs preserved 98% fluorescence which suggests their superior long-term photostability. Our results suggest that the combination of AIEgens and ET holds the potential for enhancing the efficiency of the device and extended stability of the fluorophores, two of the major requirements to allow industrial production and large-scale use of outdoor/indoor light harvesting LSCs.