In thermoelectrics,doping is essential to augment the figure of merit.Traditional strategy,predominantly heavy doping,aims to optimize carrier concentration and restrain lattice thermal conductivity.However,this tactic can severely hamper carrier transport due to pronounced point defect scattering,particularly in materials with inherently low carrier mean-free-path.Conversely,dilute doping,although minimally affecting carrier mobility,frequently fails to optimize other vital thermoelectric parameters.Herein,we present a more nuanced dilute doping strategy in GeTe,leveraging the multifaceted roles of small-size metal atoms.A mere 4％CuPbSbTe3 introduction into GeTe swiftly suppresses rhombohedral distortion and optimizes carrier concentration through the aid of Cu interstitials.Additionally,the formation of multiscale microstructures,including zero-dimensional Cu interstitials,one-dimensional dislocations,two-dimensional planar defects,and three-dimensional nanoscale amorphous GeO2 and Cu2GeTe3 pre-cipitates,along with the ensuing lattice softening,contributes to an ultralow lattice thermal conductivity.Intriguingly,dilute CuPbSbTe3 doping incurs only a marginal decrease in carrier mobility.Subsequent trace Cd doping,employed to alleviate the bipolar effect and align the valence bands,yields an impressive figure-of-merit of 2.03 at 623 K in(Ge0.97Cd0.03Te)0.96(CuPbSbTe3)0.04.This leads to a high energy-conversion efficiency of 7.9％and a significant power density of 3.44 W cm-2 at a temperature difference of 500 K.These results underscore the invaluable insights gained into the constructive role of nuanced dilute doping in the concurrent tuning of carrier and phonon transport in GeTe and other thermoelectric materials.
College of Materials Science and Engineering Shenzhen Key Laboratory of Special Functional Materials,Guangdong Research Center for Interfacial Engineering of Functional Materials,Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization,Institute of Deep Earth Sciences and Green Energy,Shenzhen University,Shenzhen 518060,China
Information Materials and Intelligent Sensing Laboratory of Anhui Province,Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education,Institutes of Physical Science and Information Technology,Anhui University,Hefei 230601,China
Superconducting Materials Research Center,Northwest Institute for Nonferrous Metal Research,Xi'an 710016,China
National Key R&D Program of ChinaNational Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaShenzhen University 2035 Program for Excellent ResearchUniversity Synergy Innovation Program of Anhui ProvinceHarbin Institute of Technology(Shenzhen)for TE module fabrication and measurement
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