Changes in efficiency of a solar cell according to various surface-etching shapes of silicon substrate

Abstract

When amorphous silicon thin film is deposited on n-type c-Si substrate, partial epi-layer of silicon grows mainly on the valley of the pyramid where two (1 1 1) planes meet. The epi-layer degrades a-Si/c-Si interface properties. This is the main cause which leads to a decrease in the efficiency of silicon heterojunction solar cells. In this study, we made various texture shapes of silicon substrate for heterojunction solar cells with n-type silicon wafers. Four different types of textures on silicon heterojunction were prepared: large textured, smoothened large textured, small textured, and smoothened small textured. Surface texturing is well known as one of the major paths to improving the efficiency of silicon solar cells by increasing the short-circuit current through effective photon trapping. The results were successful for silicon random texturing using potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH) solutions. Silicon heterojunction solar cells were fabricated on textured substrates, indicating the feasibility of KOH and TMAH texturing for solar cell fabrication. We obtained images of the surface morphology using a scanning electron microscope. The interface cross-section was taken using a transmission electron microscope. We gained the optimized surface morphology of silicon substrate for a-Si/c-Si interface in silicon heterojunction solar cells.