The ultralow thermal conductivity and tunable thermoelectric properties of surfactant-free SnSe nanocrystals

• Published in: RSC advances Vol. 11; no. 45; pp. 2872 - 288
• Main Authors: Mir, Wasim J, Sharma, Anirudh, Villalva, Diego Rosas, Liu, Jiakai, Haque, Md Azimul, Shikin, Semen, Baran, Derya
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 16.08.2021; The Royal Society of Chemistry
• Subjects: Bending machines; Chemistry; Heat conductivity; Heat transfer; High temperature; Low temperature; Nanocrystals; Power factor; Raman spectra; Room temperature; Single crystals; Surfactants; Synthesis; Thermal conductivity; Thermoelectricity; X ray photoelectron spectroscopy
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d1ra05182b

Most studies to date on SnSe thermal transport are focused on single crystals and polycrystalline pellets that are obtained using high-temperature processing conditions and sophisticated instruments. The effects of using sub-10 nm-size SnSe nanocrystals on the thermal transport and thermoelectric properties have not been studied to the best of our knowledge. Here, we report the synthesis of sub-10 nm colloidal surfactant-free SnSe NCs at a relatively low temperature (80 °C) and investigate their thermoelectric properties. Pristine SnSe NCs exhibit p-type transport but have a modest power factor of 12.5 μW m −1 K −2 and ultralow thermal conductivity of 0.1 W m −1 K −1 at 473 K. Interestingly, the one-step post-synthesis treatment of NC film with methylammonium iodide can switch the p-type transport of the pristine film to n-type. The power factor improved significantly to 20.3 μW m −1 K −2 , and the n-type NCs show record ultralow thermal conductivity of 0.14 W m −1 K −1 at 473 K. These surfactant-free SnSe NCs were then used to fabricate flexible devices that show superior performance to rigid devices. After 20 bending cycles, the flexible device shows a 34% loss in the power factor at room temperature (295 K). Overall, this work demonstrates p- and n-type transport in SnSe NCs via the use of simple one-step post-synthesis treatment, while retaining ultralow thermal conductivity. This work demonstrates tunable transport in surfactant free SnSe nanocrystals that retain ultralow nature of thermal conductivity.