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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. 

The use of nanoparticle-in-matrix composites is a common motif among a broad range of nanoscience applications and is of particular interest to the thermal sciences community. To explore this morphological theme, we create crystalline inorganic composites with nanoparticle volume fractions ranging from 0 to ∼100% using solution-phase processing. We synthesize these composites by mixing colloidal CdSe nanocrystals and In 2 Se 3 metal–chalcogenide complex (MCC) precursor in the solution-phase and then thermally transform the MCC precursor into a crystalline In 2 Se 3 matrix. We find rich structural and chemical interactions between the CdSe nanocrystals and the In 2 Se 3 matrix, including alterations in In 2 Se 3 grain size and orientation as well as the formation of a ternary phase, CdIn 2 Se 4 . The average thermal conductivities of the 100% In 2 Se 3 and ∼100% CdSe composites are 0.32 and 0.53 W m −1 K −1 , respectively. These thermal conductivities are remarkably low for inorganic crystalline materials and are comparable to amorphous polymers. With the exception of the ∼100% CdSe samples, the thermal conductivities of these nanocomposites are insensitive to CdSe volume fraction and are ∼0.3 W m −1 K −1 in all cases. We attribute this insensitivity to competing effects that arise from structural morphology changes during composite formation. This insensitivity to CdSe volume fraction also suggests that very low thermal conductivities can be reliably achieved using this solution-phase route to nanocomposites.