Search for: All records

We report the synthesis of a soluble precursor that transforms into crystalline SnSe at 200 °C. This transformation temperature is significantly lower than the 270–350 °C range of previously reported tin selenide precursors. This precursor is synthesized by reacting tin with dimethyl diselenide and we identify the precursor as tin(IV) methylselenolate using a combination of mass spectrometry, Raman spectroscopy, and nuclear magnetic resonance spectroscopy. We then chemically treat PbSe colloidal nanocrystals with this precursor and subject them to mild annealing. We characterize the chemical and structural changes during this processing using infrared spectroscopy, aberration‐corrected scanning transmission electron microscopy, and X‐ray photoelectron spectroscopy. These characterization studies indicate the successful formation of a SnSe‐like material that fills the interstitial space between the PbSe nanocrystal cores. We find that the electrical conductivity of these nanocrystal films is comparable to other excellent treatments used to improve charge transport. This excellent charge transport demonstrates the utility of tin(IV) methylselenolate as a conductive “glue” between nanocrystals.

 

We create precursors for PbTe, PbSe, SnTe, and SnSe by reacting Pb or Sn with diphenyl dichalcogenides in a variety of different solvents. We then deposit PbSe x Te 1−x thin films using these precursors and measure their thermoelectric properties. Introducing Na-dopants into the films allows the thermoelectric properties to be varied. 

There has been a growing interest in solution-phase routes to thermoelectric materials due to the decreased costs and novel device architectures that these methods enable. Many excellent thermoelectric materials are metal chalcogenide semiconductors and the ability to create soluble metal chalcogenide semiconductor precursors using thiol–amine solvent mixtures was recently demonstrated by others. In this paper, we report the first thermoelectric property measurements on metal chalcogenide thin films made in this manner. We create Cu 2−x Se y S 1−y and Ag-doped Cu 2−x Se y S 1−y thin films and study the interrelationship between their composition and room temperature thermoelectric properties. We find that the precursor annealing temperature affects the metal : chalcogen ratio, and leads to charge carrier concentration changes that affect the Seebeck coefficient and electrical conductivity. Increasing the Se : S ratio increases electrical conductivity and decreases the Seebeck coefficient. We also find that incorporating Ag into the Cu 2−x Se y S 1−y film leads to appreciable improvements in thermoelectric performance by increasing the Seebeck coefficient and decreasing thermal conductivity. Overall, we find that the room temperature thermoelectric properties of these solution-processed materials are comparable to measurements on Cu 2−x Se alloys made via conventional thermoelectric material processing methods. Achieving parity between solution-phase processing and conventional processing is an important milestone and demonstrates the promise of this binary solvent approach as a solution-phase route to thermoelectric materials.