Realized record high thermoelectric performance in n-type Bi₂Te_2.7Se_0.3 crystals via modulation doping

Cheng-Lung Chen^1*

¹Bachelor Program in Semiconductor Materials and Fabrication, Ming Chi University of Technology, New Taipei City, Taiwan

* Presenter:Cheng-Lung Chen, email:chencl@mail.mcut.edu.tw

Bismuth telluride-based thermoelectric materials are historically recognized as the best p-type (ZT=1.8) thermoelectric materials at room temperature. However, the poor performance of n-type (ZT=1.0) counterparts seriously reduces the efficiency of the device. Such performance imbalance severely impedes its thermoelectric applications either in electrical generation or refrigeration. Here, we report a strategy to boost n-type Bi₂Te_2.7Se_0.3 crystals up to ZT=1.42 near room temperature by a two-stage process, i.e., step 1: stabilizing Seebeck coefficient by CuI doping; step 2: boosting power factor (PF) by synergistically optimizing phonon and carrier transport via thermal-driven Cu intercalation in the vdW gaps. Theoretical Ab initio calculations disclose that these intercalated Cu atoms act as modulation doping and contribute conduction electrons of wavefunction spatially separated from the Cu atoms themselves, which simultaneously lead to high carrier concentration and mobility. As a result, an ultra-high PF of 63 μW cm⁻¹ K⁻² at 300 K and the highest average ZT=1.36 at 300-450 K are realized, which outperform all n-type bismuth telluride materials ever reported. The work offers a highly viable route to tune layered semiconductor materials without inducing any structural damage, paving the way for high-efficiency thermoelectric devices.

Keywords: Layered Semiconductors, Sustainable energy, Thermoelectric materials, modulation doping, Fermi level