An energy-efficient method of controlling the composite microstructure and resulting thermoelectric (TE) properties of TE composite films. The TE composite films, which include a small amount of naturally occurring chitosan binder that is sufficient to hold TE particles together, are modified by applying uniaxial mechanical pressure at low temperatures for a short duration. The TE composite films have high electrical conductivity and low thermal conductivity, making them ideal for use into high-performance energy harvesting thermoelectric devices.