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The practical operating conditions of thermoelectric products, such as the input power source and the thermal resistance of hot side heat exchanger, are different from the theoretical study. Thus the equations, which are used to estimate the practical maximum cooling performance just according to the datum in datasheet of commercial thermoelectric module (TEM), are given. The nested loop method is adopted to solve the numerical model. This study provides a method to choose a suitable TEM for thermoelectric product to meet the application requirement. It finds that the minimum cold side temperature increase and the voltage for achieving the minimum cold side temperature step decrease with the increase of thermal resistance of hot side heat exchanger, respectively. The maximum temperature difference increase and the voltage for achieving the maximum temperature difference step increase with the increase of thermal resistance of hot side heat exchanger, respectively. According to the dimension, three kinds of thermoelectric module, bulk TEM, miniature TEM and micro TEM, are studied. The novel scale effect are discovered by comparing these TEMs. It found that the step-change phenomenon become more and more obvious with the decrease of the dimension of thermoelectric module. The influence ratio of thermal resistance of hot side heat exchanger on the maximum cooling performance increases and the influence ratio of input power source decreases from macro to micro, respectively. It forecasts that there exists a critical value for the dimension of thermoelectric module, when the dimension of thermoelectric module is smaller than this critical value, the maximum voltage or current of thermoelectric module is constant and does not change with the thermal resistance of hot side heat exchanger. [ABSTRACT FROM AUTHOR]

• The phonon/electron temperature distribution in the μ-TEG leg is analyzed. • Mathematical model of μ-TEG considering interfacial and size effects is developed. • The reduction in ZT from thin film material to micro device is analyzed. • The optimization goals for contact resistivity are explored. • Optimal thermoelectric leg thickness of micro thermoelectric generator is analyzed. Micro thermoelectric generator (μ-TEG) attracts more and more attention due to its small size and high power density. Many two-dimensional thermoelectric materials with high performance have facilitated the development of μ-TEG. However, the performance of μ-TEG fabricated by these great thermoelectric materials is significantly degraded due to size effect, interfacial effects (include contact effect and boundary effect) and structure effect. To accurately assess the performance degradation degree from material to μ-TEG and guide the device fabrication, an experiment-verified mathematical model considering interfacial and size effects is proposed. Firstly, the phonon/electron temperature distribution in thermoelectric leg of μ-TEG is analyzed to investigate the device-level thermoelectric properties of material. Then based on the device-level thermoelectric properties, the actual power generation performance model of μ-TEG is established to conduct the influence analysis of these effects (boundary, size, contact and structure effects) on material and device. Finally, the thermoelectric leg thickness (H te) is optimized to realize optimal power generation. The study results reveal that boundary and size effects weaken the device-level thermoelectric properties, and the reduction trend is more obvious when H te is smaller, especially when H te ≤ 20 μm. The decrease from the material intrinsic figure of merit ((ZT) m) to the device figure of merit ((ZT) D) is owing to the boundary effect, structure effect and contact effect, and the dominant factor of this decrease changes from structure effect (H te ＜7 μm)to contact effect (H te ≥ 7 μm) as H te increases, which points to a main optimization direction for (ZT) D for different H te. As for contact effect, the electrical contact resistivity (r e,c) has a more significant impact on weakening the performance of μ-TEG than thermal contact resistivity (r k,c), and their optimization goals are explored (r e,c ≤ 5.1 × 10−12 Ω·m2, r k,c ≤ 9.3 × 10−8 K·m2/W). At given electrical and thermal contact resistivity, there exists an optimal H te for achieving the optimal power generation (P opt) and a large range of H te for achieving 95% P opt , and the optimal H te increases with increasing electrical and thermal contact resistivity. This study can reduce the processing difficulty and save time and economic costs of μ-TEG fabrication, which can avoid the blind fabrication of μ-TEG. [ABSTRACT FROM AUTHOR]

Highlights • A model of light emitting - diode with micro - thermoelectric cooler is proposed. • Various interfacial and size effects are considered in the presented model. • Five structures of micro-coolers are designed to reduce the chip temperature. • The impact of interfacial effects on the thermal performance is assessed. • The impact of micro-thermoelectric cooler on the optical performance is analyzed. Abstract Thermoelectric cooler has been widely used in the thermal management of various electronic devices. However, the application of micro - thermoelectric cooler to high power light - emitting diode still needs to be further explored at present. This paper aims to establish a model of high power light - emitting diode package integrated with micro - thermoelectric cooler and explore the performance of this system under various interfacial and size effects. An experiment is conducted to validate the model. Five types of the micro - thermoelectric coolers are designed and integrated to the light - emitting diode package to reduce the localized junction temperature of the light - emitting diode chip. The influence of interfacial effects, thermoelectric element size, and driving power of micro - thermoelectric cooler on the system - level thermal and optical performance is discussed. Results indicate that the micro - thermoelectric cooler with 6 × 6 thermoelectric elements shows the best cooling performance for the driving power of micro - thermoelectric cooler lower than 0.85 W. For thermoelectric cooler with 6 × 6 thermoelectric elements, a minimum chip junction of 95.9 °C, which is 12.3 °C lower than that of the light - emitting diode without micro - thermoelectric cooler, can be achieved. This characteristic can increase the luminous efficacy and lifetime by 12.3% and 50%, respectively. It also found that the electrical boundary resistance plays a more dominant role, compared with the thermal boundary resistance. However, the thermal contact resistance exhibits greater adverse impact than the electrical contact resistance. In addition, a total performance improvement proportion of 25.5% can still be achieved, although the micro - thermoelectric cooler consumes power energy by 22.5% at the driving power of 0.87 W. [ABSTRACT FROM AUTHOR]