Studies On Enhancement Efficiency Of Thin Film Silicon Solar Cells With High-efficiency Surface Light-trapping Structure

Thin film silicon solar cells,which can be prepared using the method of plasma enhanced chemical vapor deposition(PECVD)to realize large growth,have the advantages of low cost,simple operation and save silicon material.With the widely application of the thin film silicon solar cells,reducing the light reflection and enhancing the photoelectric conversion efficiency have become urgent research subjects for thin film silicon solar cells.Based on the theory of micro-nano optics,multiple high efficiency surface light-trapping structures were designed and developed for increase the light absorption and enhancement the photoelectric conversion efficiency of thin film silicon solar cells by the micro-nano processing technology in this research.The main content and the research results of the full text are as follows:(1)Using the micro-nano processing technology,the pit array light-trapping structures with different aspect ratio were prepared and the key processing technologies were detailed studied.(2)Thin film silicon solar cells were deposited on the another smooth surface of the prepared pit array structure glass,and the reflectance characteristics and photovoltaic properties of the the solar cells were studied.The results show that,comparing with the flat devices,the surface reflectance of the pit array structure thin film silicon solar cells is decreased by 31.91%,the average short-circuit current density are enhanced 5.75%.By the method of programming calculation,the light-trapping mechanism of the pit array structure was researched.The results show that,the surface reflectance of the hemisphere pit arrays is only 52.62% of the flat structure,the hemisphere pit arrays can reduce 31.3% internal light escape,and effectively prolongthe optical path.At the same time,FDTD simulation also shows that,with the increasing of aspect ratio of pit arrays,the reflectance of pit array structure surface reduce rapidly and finally approach to a flat.The pit array structure can reduce the light escape ability,which firstly increases and then decreases with the increasing of the aspect ratio.The reduction ability of light escape reaches a maximum when the aspect ratio is 0.8.There are 28.52% escaped light is absorbed inside the cell.The simulation also shows that the short-circuit currents of the structure solar cells are larger than that of flat cells,and the values of short-circuit current of structure cells are increased firstly and then decreased with the increasing of aspect ratio of pit arrays.The maximum of short-circuit current appears on the aspect ratio value of 1.25,and its value is promoted 10% comparing with the flat device.(3)Using the PDMS pouring process,the convex hull array structure PDMS thin film with different aspect ratio were prepared by the pit arrays structure glass templates,and then applied to thin film silicon solar cells for enhancement their light absorption and photoelectric conversion efficiency.The results show that the convex hull arrays can significantly increase the conversion efficiency and short-circuit current of the thin film silicon solar cells,and the light-trapping mechanism of that is similar to the pit array structure.FDTD simulation results show that,compared with the flat structure,the reflection of the convex hull arrays is greatly reduced,and with the increasing of the aspect ratio,the average light reflection of that reduce rapidly and finally approach to a flat.The decrease of the light escape ability for the convex hull arrays,is firstly increased and then reduced with the aspect ratio increasing.When the aspect ratio is0.75,the reduction ability of light escape reaches a maximum,it is 59.63%.The FDTD simulation also shows that the short-circuit currents of the convex hull array structure solar cells are greater than flat structure devices,and with the increasing of the aspect ratio,the short-circuit currents is firstly increased and then reduced.The maximum is appeared in the range of aspect ratio at 0.75,which shows that the short-circuit currents are improved by 15% compared with the flat cells.(4)A micro-nano pyramid structure,also named black silicon structure,was prepared on the surface of pyramid structure silicon by the method of chemical reaction etching,and their optical reflection characteristics were researched.At the same time,using the PDMS pouring technology,the PDMS thin films with invertedpyramid and micro-nano inverted pyramid structure were prepared with the templates of pyramid structure silicon and micro-nano pyramid structure silicon.At last,the inverted pyramid and the micro-nano inverted pyramid structure PDMS thin films were applied to thin film silicon solar cells for enhancement the light absorption and the photoelectric conversion efficiency of cell.The results show that,the conversion efficiency and short circuit current of the thin film silicon solar cell are obviously enhanced by the inverted pyramid and the micro-nano inverted pyramid PDMS thin films.Compared with the flat structure,the inverted pyramid structure can increase the conversion efficiency and the short-circuit density of thin film silicon by 3.11% and2.76%.And the micro-nano inverted pyramid structure can further improve the cells’ conversion efficiency and short-circuit density on the basis of the inverted pyramid structure,and finally enhancement by 5.06% and 5.36,respectively.The light-trapping mechanism research shows that the inverted pyramid and micro-nano inverted pyramid structure can obviously reduce the surface light reflections,but can not obviously reduce the light escape and prolong the optical path.(5)The haze,optical diffraction pattern and hydrophobic characteristics of the four high efficiency light-trapping structures researched in this paper were studied and discussed at last.From above,the high efficiency light-trapping structure surface can significantly improve the photoelectric conversion efficiency of the thin film silicon solar cells.This technology,on the basis of without destroying the original production process of thin film solar cells,can reduce the surface reflection,decrease the light escape and prolong the optical path,with broadband response.The technology has good popularization value,and is conducive to enhancement the performance of solar cells which are packaged by surface glass.