A.A. Raut, V.K.R. Kondapalli, N. Raut, R.J. Chapman, Y. Zhang, B.L. Kraus, H. Tran, J-H Bahk, V.N. Shanov
University of Cincinnati,
United States
Keywords: three-dimensional graphene sheets (3DGS), thermoelectric (TE) energy conversion, p-type doping, n-type doping, relative Humidity impact
Summary:
Three-dimensional graphene sheets (3DGS) with interconnected architectures offer a promising platform for next-generation flexible thermoelectric (TE) devices. In this study, we demonstrate a systematic approach to tuning the electronic properties of 3DGS through targeted doping strategies, enabling both n-type and p-type behavior for wearable energy harvesting applications. A range of polymeric and chemical dopants, including polyethyleneimine (PEI), annealed PEI (PEI-A), N-DMBI, TBD, urea, polyvinylpyrrolidone (PVP), sulfuric acid, and nitric acid, were explored to optimize charge carrier transport. Surface and electronic modifications were confirmed using X-ray photoelectron spectroscopy and Kelvin probe analysis, while TE performance was evaluated via Seebeck coefficient and conductivity measurements. Among n-type treatments, thermally annealed PEI achieved the most significant enhancement, delivering improved electron donation and stable performance. Acid-based doping yielded strong p-type characteristics suitable for complementary device integration. A prototype flexible TE module fabricated from optimized 3DGS demonstrated reliable power generation under ambient humidity, highlighting the potential of these materials for scalable, lightweight energy solutions in wearable and IoT systems.