Improved thermoelectric properties of solvothermally synthesized Bi2Te3 nanoplate films with homogeneous interconnections using Bi2Te3 electrodeposited layers

To improve the thermoelectric properties of single-crystalline Bi2Te3 nanoplate films, homogeneous Bi2Te3 layers were filled into the gaps between the nanoplates. Single-crystalline Bi2Te3 nanoplates with an approximate size of 1 μm were synthesized using a solvothermal method. The nanoplate films were prepared through a drop-casting method using methanol for nanoplate dispersion. Bi2Te3 interconnected layers were formed by electrodeposition, followed by thermal annealing to adhere the nanoplates to the electrodeposited layers. In the untreated condition, the boundaries between the Bi2Te3 nanoplates and electrodeposited layers can be clearly observed in surface field emission scanning electron microscopy images. Following thermal annealing at 250 °C, these boundaries were invisible and the films exhibited the highest electrical conductivity and Seebeck coefficient in this study. This is because the crystallinity of electrodeposited layers was improved by thermal annealing, which decreases the number of defects (reducing electron concentrations) and decreases the number of boundaries (increasing mobility). Experimental results demonstrate that the thermoelectric performance (power factor) of Bi2Te3 nanoplate films can be improved by interconnecting homogeneous electrodeposited layers and performing thermal annealing.