Lee A. Weinstein

Enhanced absorption of thin-film photovoltaic cells using an optical cavity

We show via numerical simulations that the absorption and solar energy conversion efficiency of a thin-film photovoltaic (PV) cell can be significantly enhanced by embedding it into an optical cavity. A reflective hemi-ellipsoid with an aperture for sunlight placed over a tilted PV cell reflects unabsorbed photons back to the cell, allowing for multiple opportunities for absorption. Ray tracing simulations predict that with the proposed cavity a textured thin-film silicon cell can exceed the Yablonovitch (Lambertian) limit for absorption across a broad wavelength range, while the performance of the cavity-embedded planar PV cell approaches that of the cell with the surface texturing.

Modeling of thin-film solar thermoelectric generators

Recent advances in solar thermoelectric generator (STEG) performance have raised their prospect as a potential technology to convert solar energy into electricity. This paper presents an analysis of thin-film STEGs. Properties and geometries of the devices are lumped into two parameters which are optimized to guide device design. The predicted efficiencies of thin-film STEGs are comparable to those of existing STEG configurations built on bulk materials.

Hybrid optical-thermal devices and materials for light manipulation and radiative cooling

We report on optical design and applications of hybrid meso-scale devices and materials that combine optical and thermal management functionalities owing to their tailored resonant interaction with light in visible and infrared frequency bands. We outline a general approach to designing such materials, and discuss two specific applications in detail. One example is a hybrid optical-thermal antenna with sub-wavelength light focusing, which simultaneously enables intensity enhancement at the operating wavelength in the visible and reduction of the operating temperature. The enhancement is achieved via light recycling in the form of whispering-gallery modes trapped in an optical microcavity, while cooling functionality is realized via a combination of reduced optical absorption and radiative cooling. The other example is a fabric that is opaque in the visible range yet highly transparent in the infrared, which allows the human body to efficiently shed energy in the form of thermal emission. Such fabrics can find numerous applications for personal thermal management and for buildings energy efficiency improvement.

Hybrid Optical–Thermal Antennas for Enhanced Light Focusing and Local Temperature Control

Metal nanoantennas supporting localized surface plasmon resonances have become an indispensable tool in bio(chemical) sensing and nanoscale imaging applications. The high plasmon-enhanced electric field intensity in the visible or near-IR range that enables the above applications may also cause local heating of nanoantennas. We present a design of hybrid optical–thermal antennas that simultaneously enable intensity enhancement at the operating wavelength in the visible and nanoscale local temperature control. We demonstrate a possibility to reduce the hybrid antenna operating temperature via enhanced infrared thermal emission. We predict via rigorous numerical modeling that hybrid optical–thermal antennas that support high-quality-factor photonic-plasmonic modes enable up to 2 orders of magnitude enhancement of localized electric fields and of the optical power absorbed in the nanoscale metal volume. At the same time, the hybrid antenna temperature can be lowered by several hundred degrees with respect to...

Thermal Emission Shaping and Radiative Cooling with Thermal Wells, Wires and Dots

We discuss radiative heat extraction and spectral shaping via engineering of the density of confined photon states in low-dimensional potential traps, including wells, wires, and dots. Applications include thermophotovoltaics, radiative cooling, energy up- and down-conversion.

Hybrid Optoplasmonic Structures and Materials: from New Physics to New Functionalities

United States. Department of Energy. Office of Basic Energy Science. Division of Materials Sciences and Engineering (Award No. DE - FG02 - 02ER45977)

Exceeding Solar Cell Efficiency Limit by Thermal Upconversion of Low-Energy Photons

We present a conceptual design of a new thermo-photovoltaic solar power conversion system with directionally- and spectrally-selective properties that enables the Shockley-Queisser efficiency limit to be exceeded via thermal upconversion of below-bandgap photons.