Nitrogen-doped carbon quantum dot based luminescent solar concentrator coupled with polymer dispersed liquid crystal device for smart management of solar spectrum

• Published in: Solar energy 2019-01, Vol.178, p.48-55
• Main Authors: Mateen, Fahad, Ali, Mumtaz, Oh, Heemuk, Hong, Sung-Kyu
• Format: Article
• Language: English
• Subjects: Carbon; Colorimetry; Concentrators; Cooling loads; Cooling systems; Crystals; Energy; I.R. radiation; Light; Light scattering; Lightning; Liquid crystals; Near infrared radiation; Nitrogen; PDLC; Photons; Polymers; Quantum dots; Smart materials; Smart window; Solar energy; Ultra-violet light; Ultraviolet radiation; Urban areas; Urban environments; Waveguides
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2018.12.013

•We present a planar LSC that selectively harvests UV and near UV light, and demonstrates its coupling with PDLC window device to modulate the transmission of visible and near-IR light.•Carbon QDs are synthesized that absorb the UV and near UV light and re-emit the higher wavelength light that is trapped inside a waveguide and moved towards its edges for energy generation.•Higher optical and power efficiencies (4.52% and 2.49% respectively) are achieved during OFF state of LSC-coupled PDLC device as compared to that in the ON state of PDLC. The ability of polymer dispersed liquid crystals (PDLC) smart window to electrically control the visible and near-infrared light transmissions aids to reduce the artificial lightning, heating and cooling loads in the built environment. This study presents a complementary coupling of nitrogen-doped carbon quantum dot (N-CQDs) based waveguide with PDLC smart window device that selectively harvests the ultraviolet light (UV) and near UV light for electrical energy generation without competing for the visible and near-infrared light. The hybrid device can be switchable between transmissive and opaque light scattering state while simultaneously generating electrical energy. Spectral characteristics of the light transmitted through the device confirm that UV photons are completely harvested while most of the visible and near-IR photons are transmitted. The colorimetry analysis of waveguide-coupled PDLC devices is done to realize their compatibility with visual comfort of individuals residing in the building with such windows. We eventually demonstrate that strong scattering effect during the OFF state of waveguide-coupled PDLC device is responsible for its improved optical and power efficiencies (~ 4.52% and ~ 2. 49% respectively) as compared to that in the ON state of PDLC.