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MATERIALS RESEARCH

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An analysis for geometrical effects on the cooling performance of (Bi, Sb)2 Te3yBi2 (Te, Se)3 -based thin film thermoelectric modules Il-Ho Kim and Dong-Hi Lee Department of Metallurgical Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749, Korea (Received 15 February 1996; accepted 1 August 1996)

Geometrical effects on the cooling performance of the thin film thermoelectric (TFTE) modules were investigated by varying the film thickness and the number of pyn couples of the (Bi, Sb)2 Te3yBi2 (Te, Se)3 -based system which were fabricated by the flash evaporation technique. Maximum temperature difference (DTmax, maximum cooling) and optimum input current sIopt d increased with film thickness for a fixed number of couples. For the case of given thickness, however, Iopt decreased with the number of couples, maintaining almost constant DTmax. The measured values for the cooling characteristics were compared with the results obtained through computer simulation work by the finite difference method (FDM). The thinner the film and the larger the number of pyn couples of the modules, the larger was the deviation between the experimental and the simulated values.

I. INTRODUCTION

The proper dissipation of heat evolved in microelectronic or optoelectronic devices is of primary importance because it is related to thermal noise and functional stability of the devices. It becomes more serious when devices are intended to make smaller and more highly integrated forms. There have been various investigations into the fabrication and performance characterization of thin film thermoelectric (TFTE) modules of the Bi–Sb–Te –Se systems,1–13 in light of the application to the effective temperature sensing and controlling of localized areas. The cooling performance of a thermoelectric module is affected by design parameters as well as material parameters. In this regard, there have been reports on the variation in cooling performance of the TFTE module with the aspect ratio of legs and the number of pyn couples1,3,6 or stages.4 Although the thermoelectric materials comprising a module have the optimum properties, the characteristics of a module could vary with design parameters. It is, therefore, important to make a rational basis for prediction and evaluation of cooling performance, and to understand its variation with design parameters for a TFTE module. Ioffe14 and Cadoff and Miller15 derived the mathematical formulas for the temperature distribution and the cooling power of a thermoelectric module in the 1950s and 1960s. Gwilliam16 and Spokojny et al.17 recently calculated the optimum performance and the maximum cooling power of a module with the aid of computer simulation by employing the finite element method (FEM). Chen et al.18 analyzed the effects of J. Mater. Res., Vol. 12, No. 2, Feb 1997

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heat exchanger and its thermal contact resistance on the cooling performance by assuming a one-dimensional stead