Development of High-Performance Screen-Printed Flexible Thermoelectric Generators via ZIF-67/Ag/NH2-MWCNT Composite Ink Formulations

Flexible thermoelectric generators (FTEGs) are critical to advancing sustainable, self-powered wearable electronics, but achieving high energy conversion efficiency while maintaining mechanical flexibility remains a significant challenge. Current fabrication methods often struggle to balance the need for efficient charge carrier transport with the suppression of lattice thermal transport, creating a research gap in the development of structured composite inks. Therefore, this study aims to integrate ZIF-67 and Ag/NH2-MWCNT, enabling the simultaneous optimization of thermal and electrical transport properties. ZIF-67 enhances phonon scattering through its porous framework, reducing thermal conductivity, while Ag/NH2-MWCNT significantly increases electrical conductivity by forming highly conductive percolation networks, thereby improving the overall device performance. Characterization using XRD, FESEM, FTIR, and XPS confirms the formation and chemical composition of the materials, while rheological studies demonstrate the non-Newtonian, shear-thinning behavior of the formulated ink. Our findings reveal that the nanocomposite of the optimized 2% ZIF-67 /Ag/NH2-MWCNT ink-based (AMI Z2) FTEG delivers a 1.32-fold improvement in the Seebeck coefficient, with power output and power density gains of 3.55-fold and 3.58-fold, respectively, over the pristine Ag/NH2-MWCNT ink-based (AMI) FTEG. In a p–n-type configuration involving AMI Z2 and MnO2 as the p–n type materials, respectively, the device achieves a 10.71-fold increase in the Seebeck coefficient, with remarkable 34.43-fold and 34.53-fold improvements in power output and power density compared to the AM Z2 device. Furthermore, the FTEGs exhibit stable performance across 3000 bending cycles, indicating their excellent mechanical durability. These results demonstrate a scalable, cost-effective platform for next-generation energy harvesting, bridging the gap between molecular-level morphology control and the realization of practical FTEG applications.