Flexible Thermoelectric Ag/Ag₂Se Hybrid Film

Flexible thermoelectric(TE)film,a friendly material that can directly achieve conversion between temperature difference and electrical energy.TE devices made of TE materials has attracted an increasing attention,due to its high life span,noiselessness,and adaptable to various complex geometric surfaces.Silver selenide is a room-temperature TE materials,which shows great potential in the TE applications,however,the electrical conductivity of silver selenide films is still low.Thus,the TE generator constructed by silver selenide films has a high electrical resistance,which leads to large internal wastage during operation,and therefore adverse to energy harvesting.In this paper,microwave-assisted heating method was used to synthesize Ag/Ag₂Se nano dendrites,and the TE films were prepared on nylon membrane via vacuum assisted filtration combining hot pressing process.The details are as follows:First,selenium nanowires were successfully synthesized using selenium dioxide as selenium source and ascorbic acid as reducing agent.Next,Ag/Ag₂Se nano dendrites were synthesized via a microwave assist heating method using silver nitrate as silver source,ascorbic acid as reducing agent,selenium nanowires as selenium source,and ethylene glycol as solvent.The reaction time of microwave assist heating method for preparation of the Ag/Ag₂Se nano dendrites is 15 min and the microwave power is 406 W.The possible formation mechanism of the nano dendrite was also proposed.Then,the synthesized Ag/Ag₂Se nano-dendritic powder was dispersed in deionized water,and the corresponding dispersion was obtained under ultrasound.Afterwards,Ag/Ag₂Se hybrid films with different molar ratios were prepared on nylon membrane via a vacuum-assisted filtration,followed with cold-pressing and hot-pressing treatment,which improved the density of the films.When the nominal molar ratio of Ag:Se was at 3.8:3,a highest power factor of 2436±240?W/m·K²was obtained at room temperature.Meanwhile,the flexibility,room temperature stability,and moisture resistance of the film were also tested.The results show that the film has an excellent practical performance.Finally,the hybrid films were cut into several strips with a suitable size for TE legs,and then a six-leg TE generator was assembled in an electrical series and thermal parallel connection.When the temperature difference was at 29.6 K,the open circuit voltage of the device was about 16.1 m V,the maximum output power was 6.08?W,and the corresponding maximum output density can reach 13.51 W/m².