Enhanced thermoelectric performance in organic thin films via MoO3-mediated contact resistance reduction and energy filtering

Abstract

Organic thermoelectric (OTE) devices have garnered increasing attention as promising candidates for flexible and low-cost energy harvesting technologies. However, their performance has been largely constrained by high contact resistance, particularly when using cost-effective electrode materials such as aluminum, which exhibit poor energy level alignment with organic semiconductors. Herein, we demonstrate that the incorporation of a MoO3 interlayer between Al electrodes and ethylene glycol-doped poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) effectively reduces the contact resistance by alleviating the interfacial Schottky barrier. By systematically tuning the MoO3 thickness, we achieve a maximum output power of 56.1 pW at a temperature gradient of 3 K using a 4 nm MoO3 interlayer, which surpasses the performance of conventional OTE devices employing Au electrodes by 45%. Comprehensive electrical characterizations, including the transmission line method-based contact resistance analysis and temperature-dependent conductivity measurements, reveal that the optimized interfacial energy barrier of ∼0.10 eV facilitates efficient energy filtering, enhancing the Seebeck coefficient without degrading bulk transport properties. Our findings establish an effective interfacial engineering strategy for reducing contact resistance and optimizing energy filtering in OTE devices, offering a practical pathway toward scalable and low-cost thermoelectric module fabrication.