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

Abstract

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 Cs3Cu2I5, which has a crystal structure formed of zero-dimensional [Cu2I5]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 (<0.1 W m−1 K−1). The dispersive conduction band leads to a high electron mobility (>10 cm2 V−1 s−1). For an n-type crystal at 600 K, a thermoelectric figure-of-merit ZT 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%.

Low Barrier for Exciton Self-Trapping Enables High Photoluminescence Quantum Yield in Cs3Cu2I5

“…The real part (ε 1 ) at photon energy → 0 eV is the optical dielectric constant (ε ∞ ). We obtained ε ∞ = 3.2 from the Wannier interpolation with HSE06, which is slightly lower than ε ∞ = 3.8 calculated from density-functional perturbation theory (DFPT) using the PBEsol exchange-correlation functional . This originates from the band gap underestimation by DFT/PBEsol as the optical dielectric constant is inversely proportional to the band gap .…”

“…Pristine Crystal . Because we have recently provided analysis of crystal structure and electronic band structure of Cs 3 Cu 2 I 5 , here we briefly summarize them. In Figure a, the primitive unit cell (space group Pnma ) of Cs 3 Cu 2 I 5 that contains 40 atoms is shown.…”

Two-dimensional copper based colloidal nanocrystals: synthesis and applications

“…22,37,55–61 More recently, metal halides of Cu with compositions of Cs 3 Cu 2 I 5 , Cs 3 Cu 2 Br 5 and Rb 2 CuX 3 (X = Cl, Br) have also been synthesised. 35,62 Among the metallic Cu 2D NCs seeded growth materialised NCs with PdCu and PdPtCu compositions. 63 Apart from these, many other unconventional compositions such as Cu 3 P 1− x S x and CsCu 5 S 3 have also been achieved using colloidal methods.…”

“…Moreover, they are also predicted as phonon glass electron crystals with a thermoelectric figure of merit ∼ 2.6. 35 In addition, the high ionic mobility of Cu + in a Cu-based NC lattice benefits foreign cation substitution forming multinary NCs, which is not feasible for most other 2D NCs. 36,37 These Cu-based NCs can possess both layered and non-layered structures.…”

High thermoelectric performance based on CsSnI3 thin films with improved stability

“…Recent studies have predicted zT as high as 2.6 in low dimensional metal halide perovskite derivatives. 17 Many experimental studies have reported metal halide perovskites with high Seebeck coefficient, 18,19 and ultralow thermal conductivity, [20][21][22][23][24][25] and have also reported doping methods to tune their electrical conductivity. 20,22,26 However, doping of halide perovskite materials remains challenging, which may be due to ionic compensation of charged point defects 27 and a defect tolerant electronic structure deriving from bonding orbitals at the conduction band minimum (CBM) as well as antibonding orbitals at the valence band maximum (VBM).…”