Simulation Design And Performance Optimization Of SnS Based Thin Film Solar Cells

With the increasingly serious global environmental pollution and the shortage of traditional fossil energy,solar photovoltaic power has been paid more and more attention because of its clean,safe and sustainable characteristics.In particular,the development of simple structure,high efficiency and low cost solar cells is an important direction in the future.Among them,stannous sulfide（Sn S）is a kind of direct band gap semiconductor material,which has a large optical absorption coefficient in the visible light range.The constituent elements（sulfur and tin）are abundant in nature,cheap,non-toxic and harmless,and its theoretical photoelectric conversion efficiency is as high as 25%.Therefore,Sn S thin film solar cell is a potential photovoltaic device.Due to the complexity of the actual preparation of solar cells and the uncertainty of related structure and material parameters,numerical simulation using simulation software is an effective analysis method.In this paper,the numerical simulation software wx AMPS is used to study Sn S based thin film solar cells.According to its physical characteristics,three kinds of solar cells with different structures,Mo S₂/Sn S,a-Si:H/Sn S and CZTSSe/Sn S,are designed.The effects of material thickness,doping concentration and defect states on the device performance are systematically analyzed,and the optimal cell structure and material parameters are obtained.The main results are as follows:（1）The structure of Mo S₂/Sn S solar cell was designed,and the effects of Sn S thickness,doping concentration,Gaussian defect states and band tail defect states on the performance of solar cell were analyzed.It is found that the performance of solar cells can be improved by increasing the thickness or doping concentration of Sn S in a certain range,but the performance of solar cells will be reduced if the thickness or doping concentration of Sn S is too thick.The density of states of Gaussian defects in Sn S is greater than 1×10¹⁵cm^-3,the device performance decreases obviously;For the tail defect states,when it is greater than 1×10¹⁹cm^-3e V^-1,the performance of solar cells will deteriorate significantly.Under the optimal conditions,the open-circuit voltage of Mo S₂/Sn S solar cell is 0.88 V,the short circuit current is 33.4 m A/cm²,the fill factor is 85.4%,and the conversion efficiency is 24.87%.（2）a-Si:H/Sn S solar cell was constructed,and the effects of various factors on the performance of the solar cell were studied.It is found that the thinner the a-Si:H thickness is,the better the performance of the solar cell is.Increasing the thickness of Sn S can improve the overall performance of the device.With the increase of a-Si:H doping concentration,the device performance will be improved,but it more than 1×10¹⁵cm^-3,the device performance is no longer improved;For the Sn S doping concentration is greater than 1×10¹⁵cm^-3,the short-circuit current decreases rapidly.When the density of states of a-Si:H Gaussian defects is greater than 1×10¹⁸cm^-3or the Gaussian defect density of states of Sn S is greater than 1×10¹³cm^-3,the overall performance of the cell decreased rapidly.For the tail defect states,the density of defect states in a-Si:H is greater than 1×10²²cm^-3e V^-1.The density of defect states in Sn S is greater than 1×10¹⁹cm^-3e V^-1,the device performance will be reduced.Under the optimal conditions,the open circuit voltage of the solar cell is 0.86 V,the short circuit current is 32.77 m A/cm²,the fill factor is 85.91%,and the conversion efficiency is 24.01%.（3）A CZTSSe/Sn S solar cell was constructed,and the factors of affecting the performance of the device were analyzed.The results show that increasing the thickness of CZTSSe can improve the overall performance,when the thickness of CZTSSe can reach to 0.1μm,the performance of the device does not change with the thickness;when the thickness of Sn S increases to 2μm,the performance of the device is no longer improved.Increasing the doping concentration of CZTSSe can improve the performance of solar cells,but the concentration of CZTSSe is greater than 1×10¹⁷cm^-3,the device performance does not change with the concentration;With the increase of Sn S doping concentration,other performance parameters increase,but the short-circuit current decreases.For Gaussian defect states,when the density of defect states in CZTSSe is higher than 1×10¹⁷cm^-3,or the density of defect states in Sn S is higher than 1×10¹⁴cm^-3,the performance of solar cells begans to decline.For the band tail defect state,when the density of defect states in CZTSSe is greater than 1×10¹⁹cm^-3e V^-1,or Sn S density of defect states higher than 1×10¹⁹cm^-3e V^-1,the performance of the cell will decline.After optimization,the open circuit voltage of CZTSSe/Sn S solar cell is 0.83 V,the short circuit current is 33.52m A/cm²,the fill factor is 85.6%,and the conversion efficiency is 23.92%.Through the simulation calculation of Sn S based thin film solar cells,the effects of structural parameters,material parameters and other factors on the performance of the cells are obtained,and the internal physical mechanism of the performance change is revealed.It can provides theoretical guidance and reference basis for the actual preparation of Sn S based thin film solar cells.