Texturization control for fabrication of high efficiency mono crystalline si solar cell
We studied the texturization mechanism of mono crystalline silicon wafer using some alternative additives. We successfully controlled the texture size with change of concentration of KOH in the etchant. We also proposed one appropriate model of role of additives in texturization process. In our proposed mechanism, the additives should play a role as micro-mask when the micro pyramid is formed and the texturization process should be dominated by the correlation of etching rate and adhesion and desorption rate of additives. We also fabricated solar cells with several texture sizes and evaluated them. The decrease of F.F. with the decrease of texture size was mainly caused by the increase of Rs and this result suggested that we had to optimize the screen printing and firing conditions for the small texture. In addition, there are thick damaged layer on the top and bottom of texture, and these damaged layer cause the deterioration of cell efficiency with texture miniaturization. Reduction of the damage is important to realize high efficiency solar cell using miniaturized texture.
Texturization of Si(1 0 0) substrates using tensioactive compounds
Abstract Random pyramid texturization of Si(1 0 0) substrates in alkaline solutions with addition of surface active compounds is considered. Technological difficulties connected with the application of alcohol additives are analyzed and a new solution for the wet-chemical texturization is proposed. The commonly applied alcohols in the texturization process, such as isopropanol and tertbutanol have been replaced in this work by diols (the alcohols with multiple hydroxyl groups). The results of texturization in KOH solution with 1,2-pentanediol are presented. Optimization of the solution composition and process conditions is performed. Measurements of the coefficient of light reflection carried out in the spectral range from 300 nm to 1200 nm, for the textured substrates with and without an additional anti-reflection layer are presented. The reflection coefficient for the substrates obtained in the optimal etching conditions (1 M KOH + 2% 1,2-pentanediol, 90 °C, 20 min) is close to 10%, which is comparable with the coefficient of light reflection obtained in KOH solutions with isopropyl alcohol addition. Unquestioned advantages of the solutions with diol addition (higher process temperature, shorter etching time, technological improvements) show that they can successfully replace the currently applied solutions.
Metal grids-based texturization of monocrystalline silicon wafers for solar cells
A metal grids-based texturization approach of monocrystalline silicon wafers with sodium carbonate solution is proposed. Using this etching process a low reflectance of silicon surface can be obtained for solar cells and the cost is lower than conventional texturization process. In the present work metal grids with suitable openings are used to capture hydrogen bubbles and remove them from the silicon surface, which are created due to the texturing reaction and stuck on silicon surface to prevent the texturing process. The reflectivity, the surface morphology and the etching rate are used to evaluate this texturization method. The influences of the size of the openings and the separation between grids and wafers on reflectance are studied. Under optimized conditions, uniform pyramids are fabricated. An average reflectance of 10.7% is obtained without any anti-reflectance coating.