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Scientific Papers

Luminescent Quantum Dot Films Improve Light Use Efficiency and Crop Quality in Greenhouse Horticulture

October 19, 2022
(A) Schematic of luminescent QD film technology. Shorter wavelength radiation from the sun is absorbed and down-converted to longer wavelength (lower energy) radiation via photoluminescence of a QD fluorophore. The remaining solar spectrum passes through the film to the plants below. The light emitted from the QDs is isotropic, providing a diffuse orange light to the plants below for improved full-canopy light absorption. (B) Spectral measurements of sunlight (New Mexico, 25 September 2019, 2:30 p.m., no clouds) and transmitted sunlight spectra through the QD film and a control film which contains no QDs. (C) Transmission of incident solar spectrum through the QD film (orange, solid) and through the control film (blue, dotted) compared with incident sunlight.

Abstract

The spectral quality of sunlight reaching plants remains a path for optimization  in greenhouse cultivation. Quantum dots represent a novel, emission-tunable  luminescent material for optimizing the sunlight spectrum in greenhouses with  minimal intensity loss, ultimately enabling improved light use efficiency of  plant growth without requiring electricity. In this study, greenhouse films  containing CuInS2/ZnS quantum dots were utilized to absorb and convert  ultraviolet and blue photons from sunlight to a photoluminescent emission  centered at 600 nm. To analyze the effects of the quantum dot film spectrum  on plant production, a 25-week tomato trial was conducted in Dutch glass  greenhouses. Plants under the quantum dot film experienced a 14% reduction in  overall daily light integral, resulting from perpendicular photosynthetically  active radiation transmission of 85.3%, mainly due to reflection losses.  Despite this reduction in intensity, the modified sunlight spectrum and light  diffusion provided by the quantum dot film gave rise to 5.7% improved  saleable production yield, nearly identical total fruiting biomass  production, 23% higher light use efficiency (g/mol), 10% faster vegetative  growth rate, and 36% reduced tomato waste compared to the control, which had  no additional films. Based on this result, materials incorporating quantum  dots show promise in enabling passive, electricity-free spectrum modification  for improving crop production in greenhouse cultivation, but extensive  controlled crop studies are needed to further validate their effectiveness.

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