All-Scale Hierarchically Structured p-Type PbSe Alloys with High Thermoelectric Performance Enabled by Improved Band Degeneracy
All-Scale Hierarchically Structured p-Type PbSe Alloys with High Thermoelectric Performance Enabled by Improved Band Degeneracy
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通过改善能带简并性实现具有高热电性能的全尺寸分级结构 p 型 PbSe 合金
DOI：
10.1021/jacs.9b00967
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发表时间：
2019
影响因子：
15
通讯作者：
Kanatzidis Mercouri G.
中科院分区：
文献类型：
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作者：
Tan Gangjian;Hao Snqiang;Cai Songting;Bailey Trevor P.;Luo Zhongzhen;Hadar Ido;Uher Ctirad;Dravid Vinayak P.;Wolverton Christopher;Kanatzidis Mercouri G.
我们展示了一个例子，分层设计的PbSe的电子带朝向优异的热电性能。我们发现，在室温附近，PbSe合金化15mol%PbTe时，PbSe的轻重价带能量偏移（ΔEV）变化可以忽略不计，但随着温度的升高，Δ EV的下降速率明显高于PbSe。换句话说，通过与PbTe合金化，加速了PbSe的温度诱导的价带收敛。在此基础上，在PbSe 0. 85 Te 0. 15的Pb位上添加3mol%的Cd替代，降低了Δ EV，提高了Seebeck系数。过量的Cd以CdSe 1-yTey的形式析出，其价带与p型Na掺杂的PbSe0.85Te0.15基质的价带对齐。这使得电荷能够容易地穿过基质/沉淀物界面传输，并保持高载流子迁移率。同时，PbSe 0.85Te 0.15的晶格热导率相比，显着降低到其非晶极限的0.5 W m-1 K-1。结果表明，Pb_（0.95）Na_（0.02）Cd_（0.03）Se_（0.85）Te_（0.15）体系在900 K时的最高峰值Z_T为1.7，平均Z_T为1.1（400-900 K），分别比Pb_（0.98）Na_（0.02）Se对照样品高出约70%和约50%。
We show an example of hierarchically designing electronic bands of PbSe toward excellent thermoelectric performance. We find that alloying 15 mol % PbTe into PbSe causes a negligible change in the light and heavy valence band energy offsets (ΔEV) of PbSe around room temperature; however, with rising temperature it makes ΔEVdecrease at a significantly higher rate than in PbSe. In other words, the temperature-induced valence band convergence of PbSe is accelerated by alloying with PbTe. On this basis, applying 3 mol % Cd substitution on the Pb sites of PbSe0.85Te0.15decreases ΔEVand enhances the Seebeck coefficient at all temperatures. Excess Cd precipitates out as CdSe1–yTey, whose valence band aligns with that of the p-type Na-doped PbSe0.85Te0.15matrix. This enables facile charge transport across the matrix/precipitate interfaces and retains the high carrier mobilities. Meanwhile, compared to PbSe the lattice thermal conductivity of PbSe0.85Te0.15is significantly decreased to its amorphous limit of 0.5 W m–1K–1. Consequently, a highest peakZTof 1.7 at 900 K and a record high averageZTof ∼1 (400–900 K) for a PbSe-based system are achieved in the composition Pb0.95Na0.02Cd0.03Se0.85Te0.15, which are ∼70% and ∼50% higher than those of Pb0.98Na0.02Se control sample, respectively.