Aqueous Synthesis Of Copper Indium Sulfide Nanomaterials Using CuCl As Copper Source At Room Temperature

The energy crisis and environmental pollution makes the application of solar cell has been widely concerned.In many solar cell materials,CuInS₂ has been widely concerned because of its high absorption coefficient,suitable band gap,high theoretical conversion efficiency,stable performance,low cost,low toxicity and so on.There are many kinds of synthetic methods,such as solvothermal method,magnetron sputtering,spray pyrolysis,etc.,but most of them require a vacuum,high temperature and high pressure conditions,or the use of toxic organic solvents.Harsh conditions and expensive equipment,make us realize that finding a green synthesis scheme based on a simple preparation method in mild condition with low price,low toxicity and environmental protection is significant.In early study,at first,we synthesized CuInS₂ at normal temperature and pressure in the atmospheric environment using Cu foil as copper source.But the low reaction rate leads to long reaction time.Then we use thioglycollic acid as the complexing agent of copper,and synthesized CuInS₂ at 80℃,but the reaction temperature is no longer room temperature.In the above two methods,the valence of copper source is different form the valence in the target products,which require oxidized or reduced process.Both of them use organic compounds as the sulfur source,one is thioacetamide,and the second is thiourea.Their excessive inputs will slowly decompose the poisonous gas H2S in the reaction process.In view of the above problems,in this dissertation,we want to develop a green method which has a higher reaction rate,meanwhile it does not produce toxic gas H2S.The cuprous chloride was selected as copper source which has the same copper valence with the target product CuInS₂.The reaction rate was controlled by inorganic complexing agent with a little complex complexation.The sulfur source is Na2S that is not excessive.In the end,we rapidly synthesized chalcopyrite CuInS₂ nano materials in aqueous solution at normal temperature and pressure in a one-step method.The specific work includes the following aspects:（1）NaCl as the complex of Cu⁺ to synthesis Cu-In-S nano materialsWe selected CuCl as copper source and NaCl as Cu complexing agent,synthesized chalcopyrite structure Cu-In-S nano materials with a copper indium ratio of product is 3;1 in aqueous solution at atmospheric environment and room temperature.Then,the copper indium ratio of product dropped to 2:1 by increasing the dosage of complexing agent of NaCl.It was found that further more NaCl could not reduce the copper indium ratio in the product,when the NaCl concentration reached a certain value.Meanwhile,the dosage of HCI showed an important effect on the generation of impurities.We summarized the generation conditions of pure phase Cu-In-S materials with chalcopyrite structure,and analyzed it’s mechanism.（2）NaI as the complexing agent to synthesized CuInS₂ nanomaterialsIn the above part,the copper indium ratio of products can only reach 2:1 because of the poor complexation ability of NaCl to Cu⁺.In order to reduce the ratio of indium to copper in the products,we used a little stronger complexing agent of NaI as the complexing agent of Cu⁺,and the copper indium ratio of synthesized products indeed decline as expected.When the concentration of I-was 1 mol/L,the ratio of copper to indium could reduce to 1.5:1,but it still failed to reach the stoichiometric ratio of 1:1 in CuInS₂.Finally,we synthesized CuInS₂ using NaI as the complexing agent by increasing the concentration of indium in the reactant.