Public defence, Photonics and Nanotechnology, MSc Priyanka Goel

The title of the thesis: Low-dimensional thermoelectric thin films for energy and thermal sensing applications

Thesis defender: Priyanka Goel
Opponent: Prof. Takao Mori, University of Tsukuba, Japan
Custos: Prof. Ilkka Tittonen, Aalto University School of Electrical Engineering

Turning Waste Heat into Useful Energy Through Thin-Film Materials

Every day, large amounts of energy are lost as heat from electronic devices, data centres, industrial processes and energy systems. As the use of electronics continues to grow, recovering even a small part of this wasted heat could help improve energy efficiency and improve sustainability. 

Thermoelectric materials offer one way to achieve this. They convert temperature differences directly into electricity without any moving parts. They can also be used in sensors to measure temperature and heat flow. However, their wider use is still limited by challenges in performance, large-scale production and integration with modern electronics.
This doctoral research shows how thermoelectric materials can be improved by controlling their structure at very small scale, rather than by developing entirely new materials. At the micro- and nanoscale, even small changes in structure, morphology, and interfaces can influence how heat and electrical charge are transported through a material. Understanding and controlling these changes therefore provides a way to improve material performance. The research focused on three thin-film material systems: InAlGaN, titanium nitride (TiN) and copper iodide (CuI). Using scalable thin-film fabrication techniques, it was studied how controlling growth conditions, composition and structure affects their electrical and thermoelectric properties.

A particular focus was copper iodide, a thermoelectric material that can also be transparent. By controlling how the films grow at the nanoscale, their thermoelectric performance could be improved while maintaining optical transparency. The optimized films were also integrated into devices capable of detecting temperature and heat flow, demonstrating their potential for compact thermal sensors. The thesis also explored combining copper iodide with reduced graphene oxide as another approach to improving electrical charge transport and thermoelectric properties.

Overall, the thesis demonstrates that carefully designing materials at the micro- and nanoscale can improve their performance and provide additional functionality. The findings contribute to the development of thin-film technologies for waste-heat recovery, thermal management, transparent electronics, and temperature and heat-flow sensing. In this way, heat that would otherwise be lost could become a useful source of energy and information.

Key words: Thin-film thermoelectrics, nanostructuring, composite engineering, energy harvesting, phonon transport

Thesis available for public display 7 days prior to the defence at Aaltodoc. 

Contact: 
https://www.aalto.fi/en/department-of-electronics-and-nanoengineering/micro-and-quantum-systems