Enhanced electrical and mechanical properties of Bi_(2)Te_(3)-based thermoelectric thick films enabled by a practical dynamic regulation strategy

The application of high-density and high-performance micro thermoelectric devices is still in its infancy,mainly restricted by the low performance of Bi_(2)Te_(3)-based thick film as well as the limited device inte-gration.In this study,we proposed a dynamic regulation strategy to simultaneously strengthen the thermoelectric and mechanical properties for n-type Bi_(2)Te_(3)-based thick films.The effects of growth temperature and time on thermoelectric properties have been firstly explored.As the thermoelectric properties exhibit consistent degradation with increasing thickness at static growth temperature,an effective rising temperature method is introduced to dynamically regulate the nucleation rate and growing diffusion ability.Thus,the grain refinement with compact texture structure leads to a relatively large carrier mobility(77.1 cm^(2)·V^(-1)·s^(-1))and appropriate concentration(5.25×10^(19)cm^(-3))as well as further 12%improvement of power factor with an average value up to 12.0 mW·cm^(-1)·K^(-2)over a wide temperature ranging from 313 K to 453 K.Furthermore,significant enhancement of mechanical property is also achieved with high elastic modules(56.03 GPa),hardness(0.63 GPa)and large energy dissipation capacity to prevent micro-cracks.This study provides a practical solution with dynamic temperature control to fabricate high-performance Bi_(2)Te_(3) thick films with enhanced mechanical property and pro-cessing feasibility for micro thermoelectric devices.

Combinatorial screening via high-throughput preparation:Thermoelectric performance optimization for n-type Bi-Te-Se film with high average zT>1

Thermoelectric materials have drawn extensive interest due to the direct conversion between electricity and heat,however,it is usually a time-consuming process for applying traditional“sequential”meth-ods to grow materials and investigate their properties,especially for thermoelectric films that typically require fine microstructure control.High-throughput experimental approaches can effectively accelerate materials development,but the methods for high-throughput screening of the microstructures require further study.In this work,a combinatorial high-throughput optimization solution of material properties is proposed for the parallel screening and optimizing of composition and microstructure,which involves two distinctive types of high-throughput fabrication approaches for thin films,along with a new portable multiple discrete masks based high-throughput preparation platform.Thus,Bi_(2)Te_(3-x)Se_(x)thin film library with 196 throughputs for locating the optimized composition is obtained in one growth cycle.In addition,another thin film library composed of 31 materials with traceable process parameters is built to further investigate the relationship between microstructure,process,and thermoelectric performance.Through high-throughput screening,the Bi_(2)Te_(2.9)Se_(0.1)film with(00l)orientation is prepared with a peak zT value of 1.303 at 353 K along with a high average zT value of 1.047 in the interval from 313 to 523 K.This method can be also extended to the discovery of other functional thin films with a rapid combinatorial screening of the composition and structure to accelerate material optimization.