Influence Of Nanowire AR Layer With Different Reflectivity On The Conversion Efficiency Of Monocrystalline Silicon Solar Cell

According to photovoltaic (PV) basic theory, conversion efficiency of solar cell primarily depends on optical and electrical loss. Optical loss includes surface reflection, blocking loss and spectral response of material itself. Focusing on reducing optical loss of solar cell, during the development of silicon PV industry, great efforts have been made to improve the conversion efficiency. AR layer as a solution realized by adding heterogeneous film with different refractive index or fabricating homogeneous textured structure on the substrates to reduce optical loss has always been a heated research focus. Compared with the heterogeneous film, homogeneous textured structure has shown superior advantage both in fabrication methods and its contact with the substrates.Recently, much attention has been paid to fabricating silicon nanowire as AR layer on silicon wafers by various methods such as vapor-liquid-solid (VLS), laser ablation, chemical vapor deposition (CVD), electrochemical deposition,dry etching and wet etching. Among these methods, metal-assisted electroless chemical etching shows vaster potential for future development in silicon solar cell industry for its simpler processes and cheaper cost. Even a pyramid/nanowire binary structure of monocrystalline p-type silicon wafer was reported and average reflectance of0.9%was attained by this structure. Since reducing surface reflection is prepared to improve the efficiency of solar cells, but AR layer obtained by chemical etching method is non-desired surface for photon-generated carrier transportation. There exist a contradiction between low surface reflection and high efficiency of solar cell because of surface recombination.In our research, two-step Ag-assisted electroless chemical etching method was used to attain pyramid/nanowire binary structures as AR layer on15.6×15.6cm2large area p-type monocrystalline silicon substrates. Compared black wafers were prepared to confirm the optimal AR layer of lower reflection as well as lower recommendation. It was found that shorter nanowires of200nm compared with400nm were conductive to keeping a balance between reflection and surface recommendation. Particularly, based on this optimal technological parameter, conversion efficiency of15.94%was realized.