1 research outputs found
Carrier Mobility Modulation in Cu<sub>2</sub>Se Composites Using Coherent Cu<sub>4</sub>TiSe<sub>4</sub> Inclusions Leads to Enhanced Thermoelectric Performance
Carrier
transport engineering in bulk semiconductors
using inclusion
phases often results in the deterioration of carrier mobility (μ)
owing to enhanced carrier scattering at phase boundaries. Here, we
show by leveraging the temperature-induced structural transition between
the α-Cu2Se and β-Cu2Se polymorphs
that the incorporation of Cu4TiSe4 inclusions
within the Cu2Se matrix results in a gradual large drop
in the carrier mobility at temperatures below 400 K (α-Cu2Se), whereas the carrier mobility remains unchanged at higher
temperatures, where the β-Cu2Se polymorph dominates.
The sharp discrepancy in the electronic transport within the α-Cu2Se and β-Cu2Se matrices is associated with
the formation of incoherent α-Cu2Se/Cu4TiSe4 interfaces, owing to the difference in their atomic
structures and lattice parameters, which results in enhanced carrier
scattering. In contrast, the similarity of the Se sublattices between
β-Cu2Se and Cu4TiSe4 gives
rise to coherent phase boundaries and good band alignment, which promote
carrier transport across the interfaces. Interestingly, the different
cation arrangements in Cu4TiSe4 and β-Cu2Se contribute to enhanced phonon scattering at the interfaces,
which leads to a reduction in the lattice thermal conductivity. The
large reduction in the total thermal conductivity while preserving
the high power factor of β-Cu2Se in the (1–x)Cu2Se/(x)Cu4TiSe4 composites results in an improved ZT of
1.2 at 850 K, with an average ZT of 0.84 (500–850
K) for the composite with x = 0.01. This work highlights
the importance of structural similarity between the matrix and inclusions
when designing thermoelectric materials with improved energy conversion
efficiency