| Energy utilization is the source power to promote the sustainable development of human society.To alleviate the environmental pollution caused by the massive use of fossil fuels,the research and use of clean energy are increased all over the world.As a clean,pollution-free and abundant solar energy,it is expected to replace traditional fossil fuels to a certain extent and provide green electric energy for the world.Photoelectric conversion and photothermal conversion are two effective ways of utilizing solar energy widely.The photoelectric conversion process relies on solar cells to directly convert light energy into electric energy.Photothermal conversion can be used to convert light energy into heat energy through heat collection equipment,which can then be indirectly converted into electric energy by steam turbines or thermoelectric generator.Therefore,it is necessary to study low-cost,high-efficiency and environment-friendly materials to prepare high-performance photoelectric and thermoelectric converters for the sustainable development of society.Silver sulfide(Ag2S)is a kind of narrow-band gap semiconductor material with high chemical stability and environment-friendly,which has high light absorption coefficient and wide light absorption range.It has great development prospects in the field of photoelectric conversion.In addition,the medium temperature phase of Ag2S has a band gap width equivalent to that of common thermoelectric materials,and it is also a potential thermoelectric generator material.Therefore,the research of Ag2S materials has attracted extensive attention.In this paper,Ag2S thin films with different morphologies and structures were prepared on different substrate by direct metal surface elemental reaction of in situ at low-temperature,and their photoelectric and thermoelectric conversion properties were studied respectively.The solar cell and thermoelectric generator based on the above Ag2S thin film are preliminarily assembled,and their performance is deeply studied.The main contents are as follows:1.Under different low temperature conditions(85℃,60℃ and 45℃),the elemental silver film sputtered on the substrate surface was immersed in the aqueous solution of sulfur and sodium sulfide for reaction,The Ag2S film material was quickly(the reaction time is about 3 min,8 min and 25 min respectively)formed on the substrate in situ.The effects of reaction temperature,the thickness of silver precursor and the concentration of sulfur precursor on the growth of Ag2S film were studied by XRD and SEM.It was found that the Ag2S thin film prepared by this method has the(103)crystal plane orientation and high crystallinity.The transient surface photovoltage(TSPV)test shows that the prepared Ag2S film is an N-type semiconductor with good photoelectric performance,and the photoelectric performance of Ag2S film grown at 60℃ is the best.Based on the successful preparation of Ag2S thin film,a thin film solar cell device with Ag2S as light absorption layer and P-type organic small molecule semiconductor Spiro-OMeTAD as hole transport layer was assembled.The structure is ITO/Ag2S/Spiro-OMeTAD/Au.Photoelectric conversion efficiency(PCE)of 1.34%was obtained under one standard sun.2.The Ag2S film were fabricated via direct metals surface elemental reaction by usingAg thin films withdifferent thickness on white glass substrate and S precursor solution(Na2S+S powder dissolved in DMF)at 60℃.The phase and morphology of Ag2S films was characterized by variable-temperature XRD and SEM.The Seebeck coefficient(S)and thermal conductivity(κ)of Ag2S films were measured by comprehensive physical property measurement system(PPMS),The carrier concentration(nH)and carrier mobility(μH)of Ag2S films were measured by Hall effect tester.The conductivity(σ)is obtained by calculating the resistivity.The power factor(PF=S2σ)and thermoelectric priority value(zT=S2σT/κ)of each sample were calculated according to seebeck coefficient,conductivity and thermal conductivity.The results show that the Ag2S thin films prepared by element direct reaction of low temperature have a large thermoelectric figure of merit near 600 K,which can reach 0.83 ± 0.30.This work provides a new idea for the preparation and research of Ag2S thin film thermoelectric materials.The innovation of this paper is shown in the following aspects:(1)Using the aqueous sulfur and sodium sulfide solution as the sulfur source,high crystallinity,compact and flat Ag2S films were prepared in situ by direct elements reaction at lowtemperature,and the effects of different reaction temperatures on the morphology and crystallinity of Ag2S films were analyzed;(2)The photogenerated carrier dynamics of fast-growing Ag2S film with planar surface morphology was studied,and the solar cell device based on this the Ag2S light absorption layer was assembled(PCE=1.34%);(3)The same Ag2S film prepared by this method was applied to the thermoelectric field for the first time,and a relatively high thermoelectric merit value(zT=0.83±0.30)was obtained.The Ag2S film with good photoelectric and thermoelectric properties is obtained,which is expected to promote the development of silver-based chalcogenide semiconductor materials in the fields of optoelectricity and thermoelectricity at the same time. |
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