Supporting Data for Enhancing Lettuce Yields using Quantum Dot Films

Abstract

The spectral distribution and intensity of light are critical for crop growth. One strategy is to use spectral shifting filters to passively control both the intensity and the color of transmitted sun-light, and target critical spectral ranges for optimizing photosynthesis. Copper indium sulfide/zinc sulfide (CIS/ZnS) quantum dot films have been commercially developed as spectral shifting films for greenhouses. By downshifting blue light to green and red light through photo-luminescence (PL), these CIS/ZnS films increase the transmission of more useful photons for photosynthesis. Yet, a complete understanding of how film properties impact crop yield has yet to be established. In this work, we simulated CIS/ZnS quantum dot composites at various quantum dot concentrations to determine the influence of spectral shifting on lettuce yields. At the highest concentration of quantum dots, lettuce yields increased by up to 30% relative to plants grown under the standard solar spectrum. However, increasing the amount of PL that escaped the film either by increasing the outcoupling efficiency or the PL quantum yield did not further increase yields due to the transmission of more green light. Therefore, to maximize lettuce yields, CIS/ZnS films should strongly absorb blue light without increasing the transmission of green light, favoring high concentrations of quantum dots and lower outcoupling efficiencies.