High thermoelectric properties achieved in environmentally friendly sulfide compound Bi2SeS2 by nanoenginnering

The sulfide compound BiSeS is an environmentally friendly thermoelectric material, which is as an analogy of the traditional compound BiS. Here, a high ZT value of 1.04 at 773 K is obtained through synergistically tuning the electrical transport properties by using Cu and I as the dual carrier providers and suppressing the lattice thermal conductivity by forming the Cu-rich nano-precipitates. The dual carrier providers lead to exclusively high electrical conductivity and hence a large power factor over 650 μWmK at 773 K. The atomic resolved annular dark field STEM reveals the interstitial Cu and S deficiency would result into the formation of BiCuS or CuS nano-precipitates and embed in the lattice of BiSeS, serving as strong phonon scattering. This work suggested that nanostructured BiSeS is very promising for waste heat energy harvesting in the future.