High thermoelectric and mechanical performance achieved by a hyperconverged electronic structure and low lattice thermal conductivity in GeTe through CuInTe alloying

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2023-04, Vol.11 (15), p.8119-813
• Main Authors: Kim, Hyunji, Kihoi, Samuel Kimani, Shenoy, U. Sandhya, Kahiu, Joseph Ngugi, Shin, Dong Hyun, Bhat, D. Krishna, Lee, Ho Seong
• Format: Article
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d2ta09280h

GeTe-based thermoelectric materials have a very high hole carrier concentration (∼10 21 cm −3 ), and thus, improving the figure of merit, ZT , is substantially challenging. In this work, we foremost dope Bi to lower the majority carrier concentration, followed by alloying CuInTe 2 to further adjust the hole concentration to an optimal level (0.5-2.0 × 10 20 cm −3 ). This strategy also improves the structural symmetry and leads to hyperconverged valence sub-bands and resonance levels, increasing the effective mass from 1.42 m 0 to 1.95 m 0 . Consequently, a high power factor of ∼23 μW cm −1 K −2 at room temperature and ∼41 μW cm −1 K −2 at 623 K in the (Ge 0.93 Bi 0.05 Te 0.98 )(CuInTe 2 ) 0.01 sample is reported. Moreover, the introduced point defects and nano-deposits reduce the lattice thermal conductivity to amorphous levels. As a result, the (Ge 0.93 Bi 0.05 Te 0.98 )(CuInTe 2 ) 0.01 sample has a peak ZT value of ∼2.16 at 623 K and an average ZT value of ∼1.42 at 300-773 K. A record high hardness value (∼277 Hv) is achieved. Simultaneous Bi doping and CuInTe 2 alloying appear to be an effective strategy for increasing the ZT values of GeTe-based compounds. The thermoelectric figure of merit ZT of GeTe is increased by about 77% through the optimized carrier concentration and hyperconverged electronic structure by Bi doping and CuInTe 2 alloying.