Synergistic tuning of carrier mobility, effective mass, and point defects scattering triggered high thermoelectric performance in n-type Ge-doped PbTe

Abstract

Most achievements on remarkable thermoelectric performance have been made in the intermediate-temperature p-type PbTe. However, the n-type PbTe exhibits a relatively poor figure of merit ZT, which is urgently expected to be enhanced and compatible with the p-type counterpart. Here, we report that the introduction of excessive Pb can effectively eliminate cation vacancies in the n-type Pb1+xTe−0.4%I, leading to a considerable improvement of carrier mobility μ. Moreover, further Ge doping induces a large enhancement of thermoelectric properties due to the combined effect of improved electrical transport properties and increased phonon scattering in the n-type Pb1.01Te−0.4%I−y%Ge. The Ge doping not only contributes to the increase of the Seebeck coefficient owing to the increased effective mass m∗, but also gives rise to the dramatic decrease of lattice thermal conductivity due to the strengthened point defects scattering. As a result, a tremendous enhancement of the ZT value at 723 K reaches ∼1.31 of Pb1.01Te−0.4%I−3%Ge. Particularly, the average ZTave value of ∼0.87 and calculated conversion efficiency η∼13.5% is achieved by Ge doping in a wide temperature range from 323 to 823 K. The present findings demonstrate the great potential in the n-type Pb1.01Te−0.4%I−y%Ge through a synergistic tuning of carrier mobility, effective mass, and point defects engineering strategy.

High Quality Factor Enabled by Multiscale Phonon Scattering for Enhancing Thermoelectrics in Low-Solubility n-Type PbTe–Cu2Te Alloys

“…In addition to the optimization of carrier concentration, the electronic and phonon transport properties should be rationally manipulated for further enhancing ZT. Usually, at the optimal carrier concentration, the thermoelectric performance depends primarily on the quality factor B = 4.3223 × 10 –6 × μ­( m */ m e ) 1.5 × T 2.5 /κ l , − where μ, m *, and m e are the carrier mobility, the density of states (DOS) effective mass, and the electron mass, respectively. Evidently, a high quality factor requires large DOS effective mass, high mobility, and low lattice thermal conductivity simultaneously.…”

Optimized Strategies for Advancing n-Type PbTe Thermoelectrics: A Review

“…However, the increase in m d * by band flattening might lead to a significantly reduction in mobility, because μ ∝ m b * −2/3 m I * −1 (m I *, inertial mass of the carriers along the conducting direction) when the carriers are predominantly scattered by nonpolar phonons (either acoustic or optical). 77,78 As shown in Figure 4b, the Mn-, 27 S-, 28−31 and Ge-doped 32 n-PbTe show a lower mobility with a comparison to those of Idoped-PbTe. 21 Therefore, the trade-off between mobility and Seebeck coefficients with band effective mass brings difficulties to the improvement of PF.…”

“…This review is expected to inspire new strategies on advancing n-type PbTe thermoelectrics and provide insights into the improvement of zT in other thermoelectric materials. [5][6][7][8][9][10][11][12][13][14][15][16][18][19][20][21][22][23][24][25][27][28][29][30][31][32][33][34][35][36][37][39][40][41][42]44,[47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62]…”

“…[5][6][7][8][9][10][11][12][13][14][15][16][18][19][20][21][22][23][24][25][27][28][29][30][31][32][33][34][35][36][37][39][40][41][42]44,[47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63]65,…”

Enhancing Thermoelectrics for Small-Bandwidth n-Type PbTe–MnTe Alloys via Balancing Compromise

“…Due to the symmetry crystal structure and large lattice anharmonicity, lead chalcogenide PbTe is widely utilized as a thermoelectric material in the medium-temperature region (500–900 K). , This inspires numerous efforts to improve the peak and average thermoelectric figures of merit of n-type PbTe materials to achieve a higher conversion efficiency. − However, the thermoelectric parameters are strongly coupled with each other, the compromise between carrier concentration and Seebeck coefficient ( n / S ), − the trade-off between effective mass and carrier mobility (μ/ m b * ), − even the only relatively independent parameter, and the lattice thermal conductivity, also contradictory to the carrier mobility (μ/κ l ), , which make it challenging to obtain the net enhancement of zT. Therefore, the solution of the aforementioned compromises among the thermoelectric parameters is of significance and necessary.…”