Study On The Enhancement Of Photoelectric Conversion Of Solar Cells By Two-Dimensional Micro/Nano Multi-Subparts Gratings

Because of the small size,low energy consumption and relatively simple fabrication process,the thin-film solar cells attract great attention.However,owing to the low absorption of semiconductor thin film solar cell in the band edge,especially for silicon of indirect band gap material,it greatly affects the efficiency of the thin-film solar cells.Therefore,to enhance the absorption efficiency of thin film solar cells have important significance for improving the performance of solar cells photoelectric conversion.Supported in part by the National Natural Science Foundation of China under the Grant No.11264031,Natural Science Foundation of Jiangxi Province Major Program for Youths under the Grant No.20143ACB21011,Natural Science Foundation of Jiangxi Province under the Grant Nos.20151BAB207054,20114BAB201019,Nanchang Hangkong University graduate innovation special fund under the Grant No.YC2015042,and Scientific Research Startup Foundation of Nanchang Hangkong University under the Grant No.EA201008232,in order to achieve a significant increase in the efficiency of photoelectric conversion of thin film solar cells,this paper mainly focuses on the silicon based micro/nano multi-subparts resonant gratings,explores the use of grating diffraction and resonant theory to achieve broadband,large angle,full polarized light trapping.The main contents are as follows:(1)In this study,a high performance notch filter constructed by a subwavelength front grating with micro/nano two-dimensional multi-subparts profiles is addressed.The properties of the front grating notch filter are investigated by rigorous coupledwave analysis.It is shown that over a broadband spectrum of 300~1100 nm,the structure demonstrates high transmission(>95%),and the reflectivity can be as low as 5% at the incident angle of-40°~+40°,thus the requirement of the total diffraction bandwidth,angle spectrum and polarization characteristics for solar cells can be satisfied.(2)To effectively absorb the light transmitted from the front grating into the thin film solar cell,a broadband micro/nano two-dimensional multi-subparts back grating reflector is proposed on the bottom of the active layer.Over a broadband spectrum of 300~1200 nm,the back grating reflector shows high reflectivity(>90%)above the incident angle of-35°~+35°,which means the transmission light can be reflected to the silicon active layer again to be absorbed.(3)To make full use of the front and back grating,the mentioned micro/nano twodimensional multi-subparts gratings will be introduced at both the front and back surfaces of silicon thin-film solar cell,which can enhance the photoelectric conversion performance of silicon solar cell by taking advantage of its diffractive and resonant characteristics,and as to capture and absorb broadband,wide-angle and all polarized light.The analysis shows that the silicon active layer absorption can be up to 81.8% on average with the height of 340 nm of upper micro/nano grating structure.Thus,the interaction of incident sunlight at the front and back of the micro/nano two-dimensional multi-subparts gratings,light can be better constrained in the active layer,which promotes the absorption and photoelectric conversion of light.