Metamaterial Devices for Enhancement of Thermophotovoltaics and Mid-IR Detectors.
Pfiester, Nicole.
2019
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The performance of
modern optoelectronic devices is improved if their optical properties can be finely
engineered for the application at hand. Unfortunately, constraints such as lattice
matching, dopant incorporation, and other manufacturing considerations limit what can be
done in the device itself. Manipulating the light before it hits the device can overcome
some of these design limitations. ... read moreFor example, applying a selective emitter to a
photovoltaic system can increase the conversion efficiency by better tailoring the
incident spectrum to the cell's band gap energy. Likewise, in place of dedicated pixels,
a device-wide filter that can change dynamically would increase photodetector
polarization resolution. Metamaterials, a class of man-made materials whose properties
can be designed, are well suited to solve these problems. My research focuses on
applying metamaterial devices to two applications: thermophotovoltaics (TPV) and
photodetectors. TPV systems are particularly vulnerable to parasitic losses that
decrease conversion efficiency due to their narrow band gap, making them prime
candidates for pairing with selective emitters. However, the energy sources they use,
ranging from the radioisotope heat source in deep space probes to the waste heat from
industrial processes, often operate at very high temperatures. In this dissertation, I
will present the first selective emitter made from the refractory metal iridium so that
it can withstand temperatures above 1000 °C. Its performance will be compared to my
previous work in platinum-based selective emitters. Managing polarized light is often a
consideration in photodetection applications. Metamaterial devices can be engineered to
have polarization-dependent responses through the nanostructure shape, but the response
can be enhanced or otherwise changed based on the dielectric layer underneath the
metallic nanostructures. The work presented in this dissertation has explored the
interaction with polarized light on two fronts. In the first, I show that a selective
absorber design previously shown to be angle-of-incidence independent can exhibit
enhanced reflection only at glancing angles if the dielectric layer is changed. In the
second, I created a mid-infrared polarizing filter that uses a semiconductor thin film
to enable use of a bias voltage. The bias voltage changes the metamaterial response,
making the device dynamically tunable.
Thesis (Ph.D.)--Tufts University, 2019.
Submitted to the Dept. of Electrical Engineering.
Advisor: Thomas Vandervelde.
Committee: Sameer Sonkusale, Robert White, and Jenna Walrath.
Keywords: Electrical engineering, and Materials Science.read less - ID:
- 1831cx71g
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