Preparation Of Thermoelectric Thin Films And Devices By Thermal Evaporation

Thermoelectric devices can realize the direct conversion of thermal energy to electrical energy,which can be applied in thermoelectric power generation,refrigeration and temperature sensor.In many decentralized,low-power thermoelectric conversion occasions,small or micro-thermoelectric devices have an extraordinary advantage.Preparing thin film thermoelectric device from film material is an effective approach to realize the miniaturization of device.In this paper,P-type and N-type thermoelectric thin films were prepared at different growth temperatures by thermal evaporation process.XRD and SEM techniques were used to characterize the structure of films and the thermoelectric properties were also measured.It demonstrated that the P-type Sb₂Te₃ and N-type Bi₂Te₃ films possess the maximum Seebeck coefficients of 158?V/K and-148?V/K under temperature of 260?C and 230?C,respectively.Moreover,a planar thin film thermoelectric device,which can be used as a temperature sensor,was prepared through thermal evaporation and self-aligned shadow mask method.The open circuit voltage and the output power were also evaluated.The results show that temperature sensitivity of the device was 5.40mV/K.As the temperature difference is 90 K,the open-circuit voltage is more than 0.5 V with a maximum output power of 1.105?W.The internal resistance of the device is up to 58K?.Further studies would be conducted to reduce the internal resistance so as to enhance the practical applications.Through thermal evaporation combined with shadow mask methods,we prepared the micro-scale P-type Sb₂Te₃ and N-type Bi₂Te₃ thermoelectric thin films,which can be used as micro-device thermoelectric legs.After annealing at 200?C,the Seebeck coefficients of the two films were measured by AC method and DC method,respectively,and the results were consistent with each other.In this paper,a novel method of thermal evaporation integrated with shadow mask is proposed to prepare thermoelectric thin films and devices,which provides a new solution to develop low cost and high-efficiency thermoelectric thin film materials and micro thermoelectric devices.