Experimental Study On Thermal Conductivity Of Nano Zinc Oxide Thin Films By Sol-gel Technique

Due to its advantages in environmental protection and energy supply,thin-film solar cell gradually becomes one of the most potential forms of new energy in the future.During the process of photoelectric conversion,the internal components in thin-film solar cells also accumulate relatively more heat,reducing the photoelectric conversion efficiency.In order to obtain material with high heat transfer performance,it is necessary to study the influence of the preparation process on the thermal conductivity of the material from the thermal conductivity of the components themselves.Based on the functional layer of thin-film solar cells—nano zinc oxide(ZnO)film,this paper explores the influence of the sol-gel method on its thermal conductivity.With the raw material of zinc acetate,ethanolamine and glycol ether,the precursor solutions with concentration of 0.1 mol/L,0.5 mol/L,1 mol/L and 3 mol/L respectively are produced,and the precursor film is obtained on the glass fiber by ZnO dip coating method.On glass substrate,by spin coating method,the precursor film of ZnO is obtained.In different annealing temperatures,ZnO films are obtained and the thickness of the films is measured.Transient electrothermal technique is employed to measure the thermal conductivity of internal directions along surface of ZnO films,which is gained with different precursor concentration and different annealing temperatures,and the coefficient of thermal conductivity is derived.With precursor concentration of 0.5 mol/L at 100 ? and 200 ?,ZnO thin film of 39 nm thickness is obtained.With precursor concentration of 0.1 mol/L at 100 ?,Zn O thin film of 39 nm thickness is obtained,and the coefficients of thermal conductivity of internal directions along surface of ZnO films are 4.69 W/(m·K),2.70 W/(m·K)and 0.65 W/(m·K)respectively.The results of the experiment show that,with the thickness of 17nm~39nm,at lower annealing temperature of 100 ?~ 200 ?,the coefficient of thermal conductivity of ZnO thin film is significantly lower than that of ZnO material,and decreases with the increase of annealing temperature.The coefficient of thermal conductivity increases with the increase of the thickness of the thin film.By adopting the improved transient electro-thermal method,the coefficient of thermal conductivity of ZnO film perpendicular to the internal directions along surface is studied.And with the innovative “sandwich” model,different thickness of thin film is gained under the lower annealing temperature of 100 ? ~ 300 ?,and thermal conductivity variation of ZnO with different postprocessing temperature.The experimental conclusion and transient heating technology are of the same trend.It is also found that the thermal conductivity of ZnO thin film is almost unchanged when the quenching time is prolonged.This research can provide some data reference for the thermal management and thermal design of micro electronic devices,sensors and thin-film solar cells.