Enhanced performance of graphite/NiO ink-based flexible thermoelectric generators via compositional gradient and annealing of NiO nanoparticles

This work aims at optimizing the power density of Graphite/NiO composite ink-based flexible thermoelectric generators by varying the concentration of nickel oxide nanoparticles annealed at different temperatures. NiO nanoparticles containing porous structure, higher microstrain, dislocation in their lattice structure, and higher resistivity due to the varied annealing temperature reduced the carrier concentration and mobility resulting in the enhanced Seebeck coefficient, power output, and power density. Flexible thermoelectric generator screen printed with Graphite/NiO composite ink consisting of an optimum of 3.0 wt% NiO nanoparticles annealed at 400 °C exhibited superior performance. The maximum power density, Seebeck coefficient, and power output shown by this device at 100 °C temperature gradient are 4.10 mW/m², 47.06 µV/K, and 0.80 nW, respectively. This work demonstrates the suitability of graphite and nickel oxide composite for the screen-printed flexible thermoelectric generator for low-temperature applications. Graphical abstract: [Figure not available: see fulltext.].