None-Hydrazine Solution Approach For High Performance Copper Zinc Tin Sulfur Selenium Thin-Film Solar Cells And Its Performance Optimization

Nowadays,with the declining of traditional fossil energy and environmental pollution is becoming more and more serious,solar energy is getting great attention as a new type of energy.Solar cell,one can converts solar radiation directly into electrical power,has developed rapidly in recent years.Solar cells can divided into silicon-based solar cells,multiple compounds thin film solar cells,organic polymer solar cells,dye-sensitised solar cells and quantum dot sensitized solar cells.Cu₂ZnSn?S,Se?₄?CZTSSe?thin film solar cell has gained much attention as a promising absorber material for next generation solar cell.Cu₂ZnSn?S,Se?₄ has many advantages,such as abundant elements source,adjustable band gap,high carrier concentration and so on.The methods of fabricate Cu₂ZnSn?S,Se?₄ absorber layer including vacuum approach and non-vacuum approach.In recent years,the efficiency of Solution method CZTSSe thin film solar cells has got rapidly improvement.Nowadays,the world record of CZTSSe solar cells is 12.6%,which made by Mitzi et al.with a hydrazine-based solution approach.But,hydrazine is a dangerous solvent with extremely toxicity and highly explosive.So,it's necessary to develop an environmentally-friendly and low cost solution-method to fabricate high conversion-efficiency CZTSSe solar cells.My research mainly include the following three parts:?1?In this thesis,we started with developing a environmentally-friendly solution-method to fabricate high power conversion efficiency CZTSSe solar cells.Using ethanol,1-butylanime and CS₂dissolve CuO,Zn Cl₂,SnCl₂·2.5H₂O to prepare CZTS precursor solution.About 1.2?m CZTS precursor thin films can be prepared by spinning the as-prepared precursor solution at 2500 rpm for 20s.Then we selenized precursor thin films in a graphite box at 550°C for 15 min.By this method,we fabricated Cu₂ZnSn?S,Se?₄ thin film solar cell with a power conversion efficiency of 5.41%.?2?Due to the Cu and Zn have similar atomic radius and covalent radius,it will be easy for them to cause chaos in the crystal lattice position and form antisite defect.Cu_Zn antisite defect?Cu occupy Zn lattice position?is deep level defect in CZTSSe bulk,which will cause the increase of open circuit voltage loss and become the center of charge composition.So it's go against to prepare high performance CZTSSe thin film solar cells.In order to suppress this phenomenon,we added Cd Cl₂·8/3H₂O in CZTS precursor solution to replace Zn²⁺by Cd²⁺partially.Because Cd element has large atomic radius and covalent radius,the formation of Cu_Zn antisite defect will be inhibited.When 5%Zn replaced by Cd,we fabricated CZCTSSe thin film solar cell with a power conversion efficiency of 8.11%.?3?Afterwards,we optimized chemical compositon of CZTS precursor solution.Using Thioglycolic acid instead of CS₂,dissolve Cu₂O,ZnO,SnO as metal source.In order to adjust the Se/S ratio in CZTSSe thin films,we introduce SeO₂ into precursor solution.In this method,we improved the crystalline of CZTSSe thin films and the Se/S uneven distribution phenomenon in CZTSSe thin films.In the end,when the additive amount of SeO₂ is 2 mmol,we fabricated Cu₂ZnSn?S,Se?₄ thin film solar cell with a power conversion efficiency of 9.7%.