Soluble Lead and Bismuth Chalcogenidometallates: Versatile Solders for Thermoelectric Materials

Here we report the syntheses of largely unexplored lead and bismuth chalcogenidometallates in the solution phase. Using N 2 H 4 as the solvent, new compounds such as K 6 Pb 3 Te 6 ·7N 2 H 4 were obtained. These soluble molecular compounds underwent cation exchange processes using resin chemistry, replacing Na + or K + by decomposable N 2 H 5 + or tetraethylammonium cations. They also transformed into stoichiometric lead and bismuth chalcogenide nanomaterials with the addition of metal salts. Such a versatile chemistry led to a variety of composition-matched solders to join lead and bismuth chalcogenides and tune their charge transport properties at the grain boundaries. Solution-processed thin films composed of Bi 0.5 Sb 1.5 Te 3 microparticles soldered by (N 2 H 5 ) 6 Bi 0.5 Sb 1.5 Te 6 exhibited thermoelectric power factors (∼28 μW/cm K 2 ) comparable to those in vacuum-deposited Bi 0.5 Sb 1.5 Te 3 films. The soldering effect can also be integrated with attractive fabrication techniques for thermoelectric modules, such as screen printing, suggesting the potential of these solders in the rational design of printable and moldable thermoelectrics.