Substrate Engineering of SWCNT p-n Junctions for Dual-Mode Power Generation and Heat-Flux Sensing

Area of Science:

• Materials Science
• Nanotechnology
• Thermoelectrics

Background:

• Autonomous thermoelectric power generation is crucial for self-powered Internet-of-Things (IoT) sensors.
• A key challenge is achieving continuous power generation without an external cold reservoir.

Purpose of the Study:

• To investigate substrate-dependent transitions between power generation and heat-flux sensing in single-walled carbon nanotube (SWCNT) p-n junctions.
• To establish a substrate-engineering framework for dual thermoelectric functions.

Main Methods:

• Fabrication of SWCNT p-n junction films on flexible substrates (COP, PI, PEN).
• Characterization of substrate infrared absorptivity and thermal inertia.
• Measurement of output voltage under uniform heating.
• Utilized transient thermal modeling and thermographic imaging.

Main Results:

• Substrate properties (infrared absorptivity, thermal inertia) dictate the thermoelectric behavior.
• Cycloolefin polymer (COP) substrate enabled continuous power generation (+0.38 mV).
• Polyimide (PI) and polyethylene naphthalate (PEN) substrates induced transient inverted gradients (-0.58 mV and -0.96 mV, respectively), enabling heat-flux sensing.
• Substrate optical contrast was identified as the primary switching factor.

Conclusions:

• Flexible substrates can be engineered to control the thermoelectric output of SWCNT films.
• This work provides a framework for designing SWCNT devices with dual power generation and sensing capabilities.
• The findings are significant for developing advanced self-powered sensors for IoT applications.