Preventing degradation of thermoelectric property after aging for Bi₂Te₃ thin film module

In response to growing environmental consciousness and the global commitment to reduce carbon emissions, the advancement of efficient energy harvesting has become an imperative objective. A thermoelectric device stands out for its quiet and dependable operation devoid of moving components, directly translating waste heat into electrical energy. For practical applications, the metal electrodes will be deposited on both ends of the thermoelectric thin films. The migration of atoms from these electrodes significantly influences module performance. The significance of long-term aging is critical when modules are intended for practical application. In this study, Cu and Ni were selected as electrode materials due to their commendable electrical conductivity. The investigation delves into the diffusion behavior and interfacial stability of Cu/Bi₂Te₃/Cu and Ni/Bi₂Te₃/Ni samples, unraveling insights through prolonged aging process. Cu atoms diffused into the Bi₂Te₃ film and formed Cu_2−xTe intermetallic compounds on Bi₂Te₃ surface. Conversely, Ni atoms diffuse into the Bi₂Te₃ layer by approximately 50 nm. Long-term aging, inevitably, results in degradation in the power factor (PF) of Ni/Bi₂Te₃/Ni samples, attributed to the transformation of n-type Bi₂Te₃ to p-type owing to the formation of Bi_Te^. antisite defects. However, Cu diffusion exerts a significant influence on Cu/Bi₂Te₃/Cu samples. The incorporation of Cu diffusing from the electrodes mitigates PF deterioration following extended aging. This study focuses on the effect of diffusion on thermoelectric properties and offers promising insights for enhancing the durability, efficiency, and application of thermoelectric thin film modules.