Graphene-based organic semiconductor composites for low-temperature-grade energy harvesting: From cell to module

Thermoelectric (TE) materials are promising for converting waste heat into electricity. This study presents a printable TE paste with graphene nanoplatelets (GNPs) and poly(3-hexylthiophene) (P3HT), using various filler-to-semiconductor ratios (2:1, 1:1, 1:2). The impact of the dopant Lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) and Tributyl phosphate (TBP), together with the ceramic spacer comprising Titanium oxide nanoparticles (TiO 2 NPs), has been investigated on films, pellets, and a module. For a 1:2 ratio, doping has led to significant enhancement in electrical conductivity and Power factor (PF) for the films of GNP:P3HT composite, which increased from 40 S/m to 140 S/m and 35 nW/mK 2 to 1022 nW/mK 2 , respectively. The Seebeck coefficient of the composite incorporating a TiO 2 NPs spacer reached 160 μV/K at a temperature difference of 40 ˚C. A three-dimensional structure, described as a cylindrical pellet, also resulted in notable modifications to the ratios, filler, and spacer. An optimized GNP:P3HT (LiTFSI) pellet was employed to construct a TE module for practical performance assessment. Achieving a maximum power output (P max ) of ∼0.38 μW/cm 2 for a module for a temperature difference of 35 ˚C vs room temperature, this methodology could lead to the fabrication of high-efficiency TE real devices. • A scalable approach integrates organic TE materials into a module for low-grade heat harvesting. • Thin films of the TE ink were printed on glass using a tabletop blade coater. • The composite films showed enhanced conductivity and a tunable Seebeck coefficient. • An innovative module was fabricated, elevating TE properties near room temperature..