Preparation And Properties Of Mo Back Electrode Layers And CZTSSe Absorbing Layers For Solar Cells

At present,the CZTSSe film of kesterite structure is used as a light absorption layer material for solar cells because of high light absorption coefficient(>104 cm-1),suitable band gap(0.95 eV-1.5 eV),environment-friendiness.Mo film is usually used as the absorbent layer in the back electrode,which will affect the performance of CZTSSe film directly.This thesis mainly studies the preparation and photoelectric properties of electrode Mo layer and CZTSSe film as absorption layers of solar cells.Firstly,multi-layer Mo precursor were prepared by DC magnetron sputtering,Mo films were obtained by annealing at different temperatures.Compared with the traditional process,the resistance of multi-layer Mo thin films are gradient,which conducive for the transport of carriers.Adjusting the process of preparation conditions,the single-layer Mo thin films on a glass substrate have a good phase structure and the square resistance is 1.2 ?/? when Mo target power,pressure and heat treatment temperature were 140 W,0.4 Pa and 450 ?,respectively.In order to improve the adhesion of the substrate,we prepared double-layer Mo films that have a good adhesion with the substrate and the upper square resistance is 1.7 ?/?,when the pressure ware 1 Pa and 0.4 Pa respectively.To reduce the pressure gradient,the three layers of Mo thin films were prepared and the top square resistance is 2.1 ?/? when the sputtering pressure were 1.0Pa,0.6Pa and 0.4Pa respectively,to meet the requirements of Mo back electrode.Secondly,the precursor solution was prepared by solution approach and the precursor films were obtained by spin coating process,then the as-coated precursor films were annealed and selenized to obtain CZTSSe thin films.The results indicate that the(112)diffraction peak becomes stronger with the increase of annealing temperature and the optical band gap decreases.The CZTSSe thin films have a best phase structure and smallest optical band gap of 1.32 eV annealing at 550 ?.The optical band gap decreases to 1.12 eV and crystal grains became larger and were tightly squeezed together by selenizing at 550 ? to improve the property.By selenizing with 0.4g Se,the light absorption of the thin films,which are Cu-poor and Zn-rich,is greatly enhanced in the UV-VIS spectral range,and the optical band gap decreases to 1.03 eV.