High Power Density for All‐Fe ₂ VAl‐based Thermoelectric Module by Enhancing the Power Factor of p ‐type Leg Through Defect‐Engineering and Wetting Effect

The high thermoelectric performance of Fe 2 VAl stems from its sharply rising band edges on either side of the band gap, which is highly sensitive to composition. Addressing reproducibility and scale‐up challenges, we have developed a strategy to enhance its p ‐type thermoelectric performance by defects and grain boundary engineering through regulating the V/Al ratio and In‐doping in Fe 2 V 0.85 Ti 0.1 Ta 0.05 Al. p ‐type performance of Fe 2 VAl has typically lagged behind n ‐type. In this work, a significant enhancement in power factor is realized near room temperature through a wetting effect. Additionally, a two‐step metallization process is developed for both p ‐ and n ‐type Fe 2 VAl thermoelectric legs, allowing to achieve significantly low contact resistance and maximize power output. Ultimately, a high output power density of 624 mW/cm 2 with ΔT = 327 K is achieved for the All‐Fe 2 VAl two‐pair module, 3.8 times the previous highest reported value. Despite its relatively high thermal conductivity, the impressive high power density makes it a possible choice for certain power generation and cooling applications, with benefits of material non‐toxicity, inherent stability, and high mechanical strength. This study presents a novel approach to enhancing the thermoelectric performance of p ‐type Fe 2 VAl through the wetting effect, achieving high output power density in abundant and relatively inexpensive All‐Fe 2 VAl‐based devices.