A Spectrally Tunable Dielectric Subwavelength Grating based Broadband Planar Light Concentrator

Abstract

Energy consumption of buildings is increasing at a rapid pace due to urbanization, while net-zero energy buildings offer a green and sustainable solution. However, limited rooftop availability on multi-story buildings poses a challenge for large-scale integration of photovoltaics. Conventional silicon solar panels block visible light making them unfeasible to cover all the surfaces of a building. Here, we demonstrate a novel dielectric grating based planar light concentrator. We integrate this functional device onto a window glass transmitting visible light while simultaneously guiding near infrared (NIR) portion of sunlight to edges of the glass window where it is converted to electricity by a photovoltaic cell. Gratings are designed to guide NIR region and realize polarization independent performance. Experimentally, we observe 0.72% optical guiding efficiency in the NIR region (700–1000 nm), transmitting majority of the visible portion for natural room lighting. Integrating solar cell at the window edge, we find an electrical conversion efficiency of about 0.65% of NIR light with a 25 mm 2 prototype. Major losses are coupling and guiding losses arising from non-uniformity in fabrication over a large area. Such a functional window combining energy generation, natural room lighting and heat load reduction could mitigate urban heat island effect in modern cities.

Structural, electrical, and optical properties of ITO thin films and their influence on performance of CdS/CdTe thin-film solar cells

“…Such material characterization for light-matter interactions bears a high-relevance for photo conversion applications such as solar cells. In fact, recent work on windowintegrated PC concentrators [45,46] has shown to deliver both renewable power generation whilst allowing for spectral-tuning of the optical structure to allow for natural room lighting and reduced air conditioning load on a dwelling by designing photonic structures (e.g. high contrast gratings) to reflect the infrared spectrum (reducing heat load), yet transmitting the visible portion.…”

Structure, Electrical and Optical Properties of ITO Thin Films and Their influence on Performance of CdS/CdTe Thin-Film Solar Cells

“…The Such material characterization for light-matter interactions bears a high-relevance for photo conversion applications such as solar cells. In fact, recent work on windowintegrated PC concentrators [45,46] has shown to deliver both renewable power generation whilst allowing for spectral-tuning of the optical structure to allow for natural room lighting and reduced air conditioning load on a dwelling by designing photonic structures (e.g. high contrast gratings) to reflect the infrared spectrum (reducing heat load), yet transmitting the visible portion.…”

“…In fact, recent work on window-integrated PC concentrators [45,46] has shown to deliver both renewable power generation whilst allowing for spectral-tuning of the optical structure to allow for natural room lighting and reduced air conditioning load on a dwelling by designing photonic structures (e.g., high contrast gratings) to reflect the infrared spectrum (reducing heat load) yet transmitting the visible portion. Indeed, in this study we found that interplay between material quality to solar cell performance can be extended, in principle, to high absorption atomically flat van-der Waals materials such as those belonging to the class of transition metal dichalcogenides (TMD) for light emission [47] and light detection [48,49].…”