Improvement of ds furnace and its Process parameters to grow good Quality multi crystalline silicon Ingot for solar cell application

Abstract

Multicrystalline-Silicon ingot is grown by the Directional newlineSolidification (DS) process. Multicrystallline silicon ingot quality mainly newlinedepends on stress and dislocation. Dislocations will act as the recombination newlinecentre of the device. Impurity accumulation of the ingot will be influenced by newlinethe melt-crystal (m-c) interface shape. If m-c interface is concave, impurities newlineare accumulated in the centre region. If m-c interface is convex, impurities are newlinepushed outward direction of the ingot and wall growth is prevented. Those newlinecan be controlled in two ways. First way is optimization of process parameter newlinelike slit valve opening and adjustment of the cooling rate. Second way is newlinemodification of DS furnace like additional added blocks, grooving some part newlineor making suitable modification to get the good quality mc-Si ingot for solar newlinecell application. Numerical simulation is the best tool for optimization and newlineimprovement of DS furnace, because at high temperature we can t get all the newlineinformation like temperature distribution, m-c interface, melt flow, etc., and it newlinewill help to understand the DS process in detail. From the numerical newlinesimulation we can reduce the trial runs of the DS process and save the time newlineand money. In this thesis simulation studies are done by using the CGSim newlinesoftware by using the finite volume method. The experimental studies are newlinedone by using the DSS-G1, it is supplied by the Hind High Vacuum (HHV). newlineIt has the capability to grow 20 kg mc-Si ingots. newlineDS grown mc-Si ingot quality mainly depends on the thermal stress newlineand dislocation density. These parameters are optimized and controlled by the newlineDS furnace process parameters like insulation opening, cooling recipe and newlinefurnace modification. newline