Research And Preparation Of The Absorber And Buffer Layers Based On CIGS Solar Cells

CuIn,Ga)Se2(CIGS) solar cells are highly attractive among all compound semiconductor thin film solar cells. Several attempts have focused on avoid Cu2-xSe formation during the selenization process of as-deposited CIG or CIGS layer.In CuInGaSe2-based thin film solar cells, CdS is the most extensively used materials as a buffer layer. However, due to environmental hazards connected with the production and waste disposal of CdS layers, much attention has been focused on the development of alternative buffer layers, such as InxSy and ZnS. Sputtering of InxSy and ZnS would provide a rapid deposition and is compatible with the vacuum deposition of CIGS absorbers and TCO window layer.Emphasis of this thesis is placed on optimization of the preparation of absorber and buffer layers with cost-lowering production technique--sputtering.The present study is devoted to solve the technological problems as mentioned above and the research conclusions are:1. We have optimized the rf magnetron sputtering deposition process of CIGS films by changing substrate temperature and sputtering power, and investigated their effects on crystal structure and chemical composition of CIGS films. The biggest R1here was0.9978, indicating highly pure, homogeneous and well crystallized CIGS films, which was got at substrate temperature of100℃and sputtering power of150W. Such a distinguised result was due to the controlled temperature rising during the annealing process.2. We prepared the Indium sulfide (InxSy) layers glass substrates by DC and RF sputtering respectively. We have compared the films by their surface morphology, chemical composition and optical studies and preferred the RF method. The biggest energy gap2.75eV was got at rf sputtering power of80W, which will help with efficient CIGS/InxSy solar cells.3. We applied the Orthogonal test involved with4deposition parameters:the substrate temperature, argon gas, sputtering power and annealing temperature to identify the parameters’influence on ZnS film stress and find out which parameters are more important to improve the ZnS film crystal structure or the quality of CIGS/ZnS heterostructure. Experimental results indicate that the best crystallographic ZnS film was got at substrate temperature of250℃, argon gas of1Pa, sputtering power of200W,and annealing temperature of400℃; the most promising CIGS/ZnS contained a ZnS films deposited at substrate temperature of350℃, argon gas of0.7Pa, sputtering power of 300W,and annealing temperature of400℃.Deep experiments investigated on the properties of ZnS films changed by variation of annealing temperature ranging from250℃to450℃were carried future. The biggest energy gap3.47eV was got at annealing temperature of400℃. The results are meaningful to optimize the annealing temperature of CIGS/ZnS later on.