Solution-based Synthesis And Characterization Of CuInS₂ Ternary Photovoltaic Nanomaterials

With the development of modern science and technology,energy crisis has become a common problem that many countries are faxing in the world.It has been a focused topic to find the clean and renewable energy.As an inexhaustible and renewable energy,solar energy has attracted more and more interests from 1950's and has been considered as one of the effective approaches to solve the energy problems.Recent years the rapid development of world photovoltaic?PV?market had been witnessed.However,the higher cost of PV power severely restricted its large scale applications compared with traditional thermal power generation and hydropower.Recently it has been the research hotspots to develop low-cost absorber materials and improve the conversion efficiency of solar cells.CuInS₂ is one of semiconductor materials in ?-?-?2 family compound semiconductor materials with good photovoltaic properties.Due to its nearly ideal band gap of 1.54 eV,excellent chemical stability,and high absorption coefficient about 105 cm-1,CuInS₂ has been considered as the potential candidate for absorber layer in solar cells.At present,vacuum technology was applied to prepared CuInS₂ films,which easily led to high-cost and component deviation The solution-based synthesis methods for nanomaterials provided the new strategy for preparing CuInS₂ films.Firstly nano-ink was prepared by dissolving the synthesized CuInS₂ nanoparticles into organic solvent.Then the films can be made by non vacuum techniques such as spin coating or screen printing.which can decrease the manufacturing cost.In the present synthesis processes of CuInS₂ nanomaterials,the toxic organic solvents were usually employed,accompanied by the complex techonolgy under hash reaction conditions.In this dissertation,the synthesis of CuInS₂ nanoparticles with controlled morphology and structure were studied.And based on the potential advantages of wurtzite CuInS₂ nanomaterilas on photovoltaic devices,we also explored the facile method to prepare wurtzite CuInS₂ nanoparticles under mild conditions.The CuInS₂ nanomaterials were finally synthesized by cheap and environmental materials with convenient technologies,which provided the possibility for scale production The main research contents are as follows:1.Chalcopyrite CuInS₂ nano materials were synthesized by high pressure solvothermal method and microwave assistant heating method,using CuCl,InCl3·4H2O and thiourea as raw materials and the alcohol as solvent.By using high pressure solvothermal method,CuInS₂ nano materials were synthesized at 180 ? for 32 h with aforementioned precurssors.SEM images indicated the CTAB addition amount had important impact on the morphology of final products.Although the products had the similar spherical structure,there had distinctive difference in the nanoparticles which formed the microspheres.The morphologies of CuInS₂ nanoparticles changed from worm-like,cuboids,flakes to amorphous grains.The rectangular CuInS₂ nanoparticles with chalcopyrite structure were finally synthesized at 180 ? for 32 h by using alcohol as solvent and CTAB as surfactant.2.As comparison,Chalcopyrite CuInS₂ nanomaterials were also synthesized at 180 ?for 90 min using microwave heating method with the same materials.The reaction time was effectively shortened by microwave heating method.The effects of different solvents or Cu-sourse were also studied in this method.3.The CuInS₂ nanoparticles were prepared by atmospheric pressure solvothermal method with different Cu-sources using EG as solvent.The chalcopyrite CuInS₂ was synthesized by using CuSO4·5H2O,InCl3·4H2O and thiourea as precurssors at 185 0C for 4 h.However,the flake spheres were synthesized when CuAc2·H2O was used as Cu-source with the same reaciton system.XRD and XPS results showed the products had the co-existed phase of chalcopyrite and wurtzite.To prepare the pure phase CuInS₂,the hot injection method was used to change the additon order of S-source.The morphologies of the nanopowders changed from flake-spheres to nanorods and nanoplates when hot injection mehod was used with the same precurssors of CuAc2·H2O,InCl3·4H2O and thiourea.Finally by hot injeciton method,chalcopyrite CuInS₂ nanoparticles were synthesized by using PAL and ODE as solvent at 240 ? for 30 min,with the precursors of CuAc2·H2O,InCl3·4H2O and thiourea.4.Based on the atmospheric pressure solvothermal method,the hot injection method was developed to synthesize the wurtzite nanomaterials.The triethanolamine was employed as solvent during the synthesis processes.The different Cu-source were used in the hot injection reaciton processes and the products had the similar morphology of nanoplates.However,XRD and XPS results showed the products had the co-existed phase of chalcopyrite and wurtzite.The strong polarity and mutual interaction were considered as the reasons that resulted in various release rates of Cu-ions during the nucleation stage.XRD results with different reaction time proved the processes.5.Wurtzite CuInS₂ nanoparticles were synthesized at 140 0C for 1 h by hot-injection method using monoethanolamine as solvent with different Cu-precurssors.The reaction time was 1 h when CuAc2·H2O and CuSO4·5H2O were used as Cu-source,while the time could be reduced to 30 min when CuCl was used as Cu-source.The synthesis process can be finished in 5 min by adding surfactant of PEG,which showed CuCl had higher reaction activity in MEA system.CuSbS₂ nanoparticles were also synthesized at 140 0C for 1 h using the same method,which showed monoethanolamine system had the large application space in the synthesis of ternary semiconductor materials.The monoethanolamine solvent employed here is cost-effective and the facile reaction process takes place under relatively mild conditions,which means the potential value in applications.