The NQPI Seminar Series

features Mariama Rebello Sousa Dias of the Department of Physics at the University of Richmond discusses Advancements in the Design of Optical Components for Efficient Optoelectronic Devices Operating at High Temperature on April 27 at 4:10 p.m. in Clippinger 194.

Abstract : Using nanostructures with different chemical compositions and geometry is a promising way to improve the performance of optical sensors, energy harvesting devices, and photocatalysts. However, photonic materials for high-temperature applications must withstand their temperature operation while keeping their function. In the first part of this talk, I will highlight recent progress in using alloys with different chemical compositions as a pathway to control and tune their optical response. To determine the ideal composition for a particular application, we use a combination of traditional material synthesis and characterization methods, simulation, and modeling methods. In particular, Au-Al has shown to be promising for sensor applications operating at high temperatures. Here, we designed an artificial neural network trained to predict an Al-Au system's dielectric response. To confirm our prediction, we fabricated bimetallic films with different compositions and measured their optical response at different temperatures. We find that the accuracy of the ML is very high, and the time response is relatively short. Moreover, we show that all alloys outperform their pure counterparts in sensitivity, with Au _0.85 Al _0.15 ­ being the best candidate for replacing pure gold in sensors based on the surface plasmon resonance effect. This approach can expand optical properties databases of known and hypothetical systems.

In the second part, I will report the recent advancements in emitter design for thermophotovoltaics (TPVs). In thermophotovoltaics, heat from a thermal emitter is directly converted to electricity via a photovoltaic (PV) cell. One way to decrease system losses is to tailor the emitted spectrum to a specific PV cell. In this work, we propose to use a thin film configuration for the emitter. We define a figure of merit (FOM) as the ratio of the power generated by the photovoltaic cell () and the power emitted by the emitter (). We analyze the optimal configuration of >2000 emitters that can operate at temperatures above 2000 ºC. The methods implemented here apply to any PV cell. Thus, we evaluate the best emitter candidates for Si, Ge, GaSb, InGaAs, and InGaAsSb cells. Due to the ultra-high temperature operation of the thermophotovoltaic, the thermal stability and the mismatch in the thermal expansion coefficient of each material combination are discussed. Our results show that FOMs above 50% are achievable under ideal conditions. This work can shed light on high-temperature photonics, where a simple emitter design can result in higher efficient photoelectronic devices.

Brief Bio :  Mariama R. S. Dias is an Assistant Professor at the University of Richmond. She received her Ph.D. in Physics from The Federal University of Sao Carlos, Brazil, in 2014. During her Ph.D., she held visiting research appointments at the Ohio University, The Free University of Berlin, and The University of Wuerzburg. Before arriving at UR, she was a postdoctoral researcher at the University of Maryland, holding the Schlumberger Faculty for the Future Fellowship. Dr. Dias’ lab currently researches topics that focus on metallic, oxide, and semiconductor nanostructures with potential applications in optics, plasmonics, nanoelectronics, and energy harvesting devices.