Yosuke Inomata

Surface texturing of large area multicrystalline silicon solar cells using reactive ion etching method

Abstract A reactive ion etching method has been applied to form a surface texture of multicrystalline silicon solar cells in order to reduce the surface reflectance. This surface texture has a pyramid-like shape, and aspect ratio of which can be easily controlled by the gas flow ratio. 15 cm × 15 cm multicrystalline silicon solar cells have been fabricated using this texturing method and maximum conversion efficiency of 17.1% has been achieved.

Surface texturing using reactive ion etching for multicrystalline silicon solar cells

We have developed a new surface texturing technique using a reactive ion etching (RIE) method for multicrystalline silicon (mc-Si) solar cells, which is expected to form a low reflectance surface on grains of various crystalline orientations. This surface texture has a cone shape, and aspect ratio and size of which can be easily controlled. We have optimized surface shape and emitter sheet resistance. The optimum emitter sheet resistance for RIE textured cell is higher than that for the usual cell. The high aspect ratio of the cone shape makes surface reflectance low, but the cell efficiency is not so good. There is an optimum aspect ratio because the emitter of cell with high aspect ratio surface has large saturation current and cell performance is decreased with aspect ratio. We have fabricated over 17% efficient large area (225 cm/sup 2/) mc-Si solar cell using this surface texturing technique and passivation schemes which is based on the silicon nitride film deposited by the plasma CVD method and hydrogen annealing at a high temperature.

17.7% efficiency large area multicrystalline silicon solar cell using screen-printed metallization technique

This paper describes the development of an industrial processing sequence that employs the screen printing and firing for large area multicrystalline silicon (mc-Si) solar cells. A record high efficiency mc-Si solar cell of 17.7%; cell area: 232.5 cm/sup 2/ has been achieved using Kyoceras original cast mc-Si material. The diffusion length of mc-Si material was improved after cell processing especially at the region that had low diffusion length by gettering or passivation effects. The diffusion length after cell processing was about 270 /spl mu/m, and this value corresponds to the value estimated internal quantum efficiency curve of PC-1D simulation very well. The photovoltaic module has been fabricated using 48 cells that have average efficiency of 17.2% with this type of cell. The record module efficiency of 15.7% has been achieved.

Surface and bulk-passivated large area multicrystalline silicon solar cells

Abstract We have investigated the surface and bulk passivation technique on large-area multicrystalline silicon solar cells, a large open-circuit voltage has been obtained for cells oxidized to passivate the surface and hydrogen annealed after deposition of silicon nitride film on both surfaces by plasma CVD method (PSiN) to passivate the bulk. The texture surface like pyramid structure on multicrystalline silicon surface has been obtained uniformly using reactive ion etching (RIE) method. Combining these RIE method and passivation schemes, the conversion efficiency of 17.1% is obtained on 15 cm × 15 cm multicrystalline silicon solar cell. Phosphorus diffusion, BSF formation, passivation technique and contact metallization for low-cost process sequence are also described in this paper.

Over 16% efficiency large area-multicrystalline silicon solar cell

Since 1989, Kyocera has been carrying out research into high efficiency solar cells using multicrystalline silicon substrates (15 cm/spl times/15 cm) made by the Sumitomo Sitix Co. Ltd. The bifacial Silicon nitride solar cell (BSNSC) fabrication process developed by Kyocera has been applied to this large area solar cell. A conversion efficiency of 16.4% (global AM 1.5, 100 mW/cm/sup 2/, 25/spl deg/C) for the 15 cm/spl times/15 cm multicrystalline silicon solar cell has been obtained by optimizing the front surface structure to reduce the reflective losses, and by improving the front electrode pattern using an evaporation method.<<ETX>>