Magnetic ions in wide band gap semiconductor nanocrystals for optimized thermoelectric properties

Abstract

Here we propose a new concept in which incorporated magnetic ions create spin entropy, a narrowed band-gap and stronger anharmonic phonon coupling to obtain a larger Seebeck coefficient, higher electrical conductivity and lower thermal conductivity for significant improvement of the ZT value. This idea is experimentally achieved both with magnetic ion doping and full substitution of quaternary chalcogenide nanocrystals: the ZT value of Ni-doped Cu₂ZnSnS₄ is extraordinarily enhanced by 7.4 times compared to that of pure Cu₂ZnSnS₄, while Cu₂CoSnS₄ shows a 9.2 times improvement.