Ionic Coordination and Hierarchical Architecture Enable Record n-Type Thermoelectric Efficiency in Soft Hydrogels

Area of Science:

• Materials Science
• Energy Harvesting
• Thermoelectrics

Background:

• Ionic thermoelectric materials offer advantages like flexibility and stability for low-grade heat energy conversion.
• While p-type ionogels are well-developed, efficient n-type analogues remain a significant challenge in the field.

Purpose of the Study:

• To design and synthesize a high-performance n-type ionogel for thermoelectric applications.
• To investigate the mechanisms responsible for enhanced thermoelectric properties in the developed material.

Main Methods:

• Fabrication of a poly(vinyl alcohol) (PVA)-based ionogel incorporating PEDOT:PSS, ionic liquid, and zinc bromide.
• Annealing process to induce strong coordination and form anion-rich clusters, optimizing ion transport.
• Characterization of ionic conductivity, thermal conductivity, thermopower, and power factor.

Main Results:

• Achieved a remarkable thermopower of -128 mV K⁻¹ and an ultrahigh power factor of 16.7 µW cm⁻¹ K⁻².
• Obtained an excellent thermoelectric figure of merit (ZT) of 1.1 at room temperature.
• Demonstrated a balanced high ionic conductivity and low thermal conductivity due to hierarchical ionic architecture.

Conclusions:

• The developed n-type ionogel represents a significant advancement in flexible thermoelectric materials.
• The strategy provides a universal approach for designing high-performance n-type ionic thermoelectrics.
• Opens new possibilities for flexible, sustainable heat-to-electricity conversion technologies.