Chalcogenide Flexible Thin Film Thermoelectric Device

Fabricated by Co-Sputtering J. Yao1,2 and D. W. Hewak2

1 Advanced Composite Materials Facility, Chemistry, University of Southampton, SO17 1BJ

2 Optoelectronics Research Centre & Novel Glass Group, University of Southampton, SO17 1BJ

References

[1] A. Minnich, et al., Energy Environ. Sci., 2009, 2, 466-479 [2] AJA International, INC. [3] Laird Technologies. [4] H. Zou, et al., Journal of Crystal Growth, 2001, 222, 82-87 [5] I. H. Kim, Materials Letters, 2000, 43, 221-224

Co-Sputter Thin Film Growth Technique

Advantages: • Rapid, stable process with uniform

thin film quality.

• Bismuth Tellurium alloys deposited at 200oC and room temperature.

• Carrier type reversal observed in BiTe thin film when deposited at 200oC.

Schematic of Sputtering, reprinted from [2]

Thin Film Analysis and Device Characterisations

TE device fabricated on flexible polyamide substrate

n-type Bi2Te3 and p-type Bi0.5Sb1.5Te 3 thin film

XRD results of Bi2Te3 and Bi0.5Sb1.5Te3 thin films deposited by sputtering at 200oC

XRD results follow the JCPDS database.

SEM images of a)as-deposit Bi0.5Sb1.5Te3 , b) as-deposit Bi2Te3, c)Bi0.5Sb1.5Te3 deposited @200oC and d) Bi2Te3 deposited

@200oC.

• Bi0.5Sb1.5Te3 and Bi2Te3 thin films were crystallized when sputtered at 200oC.

• Granular structure on the surface of Bi2Te3 thin film indicates the stoichiometric composition.

Device Fabrication and Applications

In House fabrricate TFTE device characterisation kit. 0.25V output voltage measured when 50K temperature difference

between hot and cold sides.

Classic bulk TE device [1]

ZT = 𝑆2𝑇

𝜌𝜆

Figure of merit (ZT) depends on Seebeck coefficient S, thermal conductivity λ, and electrical resistivity ρ. λ = heat capacity ×material density × thermal diffusivity

Thermoelectric effect is a solid-state physics phenomena that describes the direct conversion of temperature difference to electric voltage and vice versa. The figure of merit (ZT) indicates the efficiency of different TE materials.

The thin film TE design has numbers of advantages, such as: Cost effective, higher theoretical ZT value and more novel designs & applications

p and n-type TE materials characteristics

Open-circuit voltage, internal resistance and output power of the TFTE device

Stacking design

FEI Helios NanoLab DualBeam FIB/SEM

What is Thermoelectric (TE) and Why Thin Film?

Acknowledgements EPSRC and Novel Glass Group, ORC, University of Southampton

Acknowledgements This work was supported in part by EPSRC Grant EP/I019065/1 “AMORPHOUS CHALCOGENIDE-BASED OPTOELECTRONIC PLATFORM FOR NEXT-GENERATION OPTOELECTRONIC TECHNOLOGIES”.

We also acknowledge support through the EPSRC Centre for Innovative Manufacturing in Photonics”.

We are grateful for the technical support of Mr Chris Craig and Mr Ed Weatherby.

Useful discussions which provided valuable background for this work were held with Dr R.J. Curry, R.M. Gwilliam, K.P. Homewood and M.A. Hughes (University of Surrey) and Prof S.R. Elliott and Dr T.H. Lee (Cambridge).