Prediction of high thermoelectric performance in the low-dimensional metal halide Cs3Cu2I5

Metal halides have emerged as a new generation of semiconductors with applications ranging from solar cells to chemical sensors. We assess the thermoelectric potential of Cs 3 Cu 2 I 5 , which has a crystal structure formed of zero-dimensional [Cu 2 I 5 ] 3− anionic clusters that are separated by Cs + counter cations. We find the compound exhibits the characteristics of a phonon-glass electron-crystal with a large imbalance in the conduction of heat and electrons predicted from first-principles transport theory. Strong anharmonic phonon–phonon scattering results in short-lived acoustic vibrations and an ultra-low lattice thermal conductivity (10 cm 2 V −1 s −1 ). For an n-type crystal at 600 K, a thermoelectric figure-of-merit Z T of 2.6 is found to be accessible, which for a cold source of 300 K corresponds to a thermodynamic heat-to-electricity conversion efficiency of 15%.