Performance Research And Simulation Modeling Of Flexible CIGS Solar Cells

Currently,CIGS（Copper indium gallium selenide）thin film solar cell technology is one of the most efficient thin film solar cell technology.It represent the most promising thin film solar cell technology.CIGS thin film solar cells on flexible substrates have a wide market in commercial,civil and military applications.Nowadays,researchers in this area are focusing on the improvement of the flexible CIGS solar cell performance.In this paper,the performance of CIGS thin film solar cells based on polyimide substrates was studied by simulation and experimental analysis.Alkali metal doping and back contact improvement were used to improve the performance of solar cells.In the first part,a defect passivation model is established.The calculation shows that passivation of OVC（Ordered Vacancy Compound）layer and absorption layer plays a major role in improving the performance of CIGS solar cells.In order to ensure the performance of the solar cell,the length of passivation zone should be greater than that of space charge zone.Considering the defect passivation model,the effect of post deposition treatment is better than pre-deposition treatment under the same preparation conditions.Samples were prepared by different doping methods of alkali metals.It was found that the growth kinetics of CIGS films was affected by the addition of alkali metals.However,electrical properties were worse than those of samples doped with alkali metals,no matter which doping method was used.It is proved that the defect passivation of alkali metal can improve the performance of the solar cell.In the second part,a back-contact model is established to simulate the p-type MoSe₂interface layer between CIGS absorbing layer and back-contact layer Mo.Mo/MoSe₂ is Schottky contact,MoSe₂/CIGS is ohmic contact.And MoSe₂ interface layer forms quasi-ohmic contact between back-contact Mo and CIGS absorbing layer,which shows the importance of forming MoSe₂ layer for improving back-contact performance.Increasing the sputtering power of Mo will increase the density of Mo surface,thus increasing the thickness of MoSe₂ layer.Under the pre-deposition treatment Na,Na₂Se_x can be generated to inhibit the formation of MoSe₂ layer and reduce the back-contact performance.Pre-deposition treatment Na results worse grains at the bottom of the absorption layer and inhibits the growth of MoSe₂ layer,which is the reason for the poor performance of pre-deposition treatment Na samples.The highest sample efficiency is 11.05%.After post deposition treatment Na and K,the thickness of MoSe₂ layer is about 110 nm.