As much as half of US energy production each year is lost as waste heat. Converting waste heat into electricity could improve energy efficiency dramatically and sharply reduce greenhouse gas emissions. Thermoelectric (TE) devices convert temperature differences into electrical power and have the potential to revolutionize the nation's energy portfolio. An ideal thermoelectric material conducts electricity, but not heat. Metals conduct both, whereas insulators conduct neither. This project challenges this dichotomy by using a novel strategy to dope tungsten disulfide, a two-dimensional (2D) semiconductor. We will enhance its thermoelectric coefficient to maximize the output voltage, increase the electrical conductivity to minimize losses, and lower the thermal conductivity to maintain a large temperature difference. The proposed research will lead to efficient devices for waste heat recovery. This work will also enable high-performance 2D transistors, low-power memory devices, and nanoscale switches for thermal management. The team will work closely with local communities to encourage participation by students from all backgrounds in engineering careers and foster interest in nanotechnology. Outreach efforts will include lab demonstrations, summer internships, and career workshops.
The goal of this project is to improve the in-plane thermoelectric efficiency of two-dimensional tungsten disulfide (WS2) devices through engineering their electrical, thermal, and thermoelectric properties via electrochemical intercalation. WS2 has recently emerged as a promising TE candidate due to its large atomic mass (low thermal conductivity), small bandgap (high electrical conductivity), and high Seebeck coefficient. However, it remains challenging to optimize all of the material properties to maximize its TE efficiency and to dope this 2D material to create the p- and n-type pairs needed for TE devices. In this work, we will: (1) achieve p- and n-type doping in 2D materials via anion and cation intercalations; (2) optimize the in-plane power factor of WS2 through doping; (3) reduce the in-plane thermal conductivity of WS2 via phonon scattering by intercalants. Fundamentally, this project will study electrical, ionic, and thermal transport in 2D materials. Practically, this work will pave the way for the wide use of thermoelectric devices to scavenge heat from sources such as electronics and the human body. This work will also develop a doping method for 2D materials, addressing critical issues in 2D electronics such as low drive current and poor contact resistance.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
