Cast-mono crystalline silicon wafers contain crystallographic defects, which can severely impact the electrical performance of solar cells. This paper demon- strates that applying hydrogenation processes at moderate t...Cast-mono crystalline silicon wafers contain crystallographic defects, which can severely impact the electrical performance of solar cells. This paper demon- strates that applying hydrogenation processes at moderate temperatures to finished screen print cells can passivate dislocation clusters within the cast-mono crystalline silicon wafers far better than the hydrogenation received during standard commercial firing conditions. Efficiency enhancements of up to 2% absolute are demonstrated on wafers with high dislocation densities. The impact of illumination to manipulate the charge state of hydrogen during annealing is investigated and found to not be significant on the wafers used in this study. This finding is contrary to a previous study on similar wafers that concluded increased H or H0 from laser illumination was responsible for the further passivation of positively charged dangling bonds within the dislocation clusters.展开更多
Multi-crystalline silicon ingots produced using directional solidification systems(DSS)represent the best way to obtain high quality crystalline silicon at low prices and with high throughputs.The DSS technology is wi...Multi-crystalline silicon ingots produced using directional solidification systems(DSS)represent the best way to obtain high quality crystalline silicon at low prices and with high throughputs.The DSS technology is widespread among PV silicon ingot producers and hundreds of furnaces are manufactured worldwide every year.The present challenge for crystal growers is to increase the quality of ingot and to reduce the specific energy consumption and cost. The first goal can be reached by changing the DS process to a Mono-Like-Casting process,while the second one has pushed some companies to develop new DSS furnaces able to grow ingots up to 800 kg.The main features and the characteristic design of the hot-zone in the iDSS(induction-DSS)furnace are presented,also in comparison with the standard DSSs ones.The reduction of the thickness of insulation boards,the smaller size of the hot-zone and the selective lateral induction coil system lead to an optimal control of the thermal instabilities into the silicon melt,increasing the ingot quality.In fact,the lateral induction coil system is equipped with independent turns connections and it can be used to force selectively-at different vertical positions-the most suitable thermal condition.In this way,one is able to compensate the radiative thermal losses and create a 'virtual' adiabatic wall,producing a planar solidification front or modeling the radial thermal gradient in order to obtain the desired solidification front shapes.In previous papers,the authors have presented some preliminary results obtained with a iDSS furnace^([4][5][6]).In the present paper is proposed a discussion about the numerical analysis of Mono-Like-Casting process with iDSS furnace capacity up to 120 kg of silicon feedstock.The furnace is actually under construction in the context of research activities of PFV(Polo Fotovoltaico Veneto).展开更多
文摘Cast-mono crystalline silicon wafers contain crystallographic defects, which can severely impact the electrical performance of solar cells. This paper demon- strates that applying hydrogenation processes at moderate temperatures to finished screen print cells can passivate dislocation clusters within the cast-mono crystalline silicon wafers far better than the hydrogenation received during standard commercial firing conditions. Efficiency enhancements of up to 2% absolute are demonstrated on wafers with high dislocation densities. The impact of illumination to manipulate the charge state of hydrogen during annealing is investigated and found to not be significant on the wafers used in this study. This finding is contrary to a previous study on similar wafers that concluded increased H or H0 from laser illumination was responsible for the further passivation of positively charged dangling bonds within the dislocation clusters.
文摘Multi-crystalline silicon ingots produced using directional solidification systems(DSS)represent the best way to obtain high quality crystalline silicon at low prices and with high throughputs.The DSS technology is widespread among PV silicon ingot producers and hundreds of furnaces are manufactured worldwide every year.The present challenge for crystal growers is to increase the quality of ingot and to reduce the specific energy consumption and cost. The first goal can be reached by changing the DS process to a Mono-Like-Casting process,while the second one has pushed some companies to develop new DSS furnaces able to grow ingots up to 800 kg.The main features and the characteristic design of the hot-zone in the iDSS(induction-DSS)furnace are presented,also in comparison with the standard DSSs ones.The reduction of the thickness of insulation boards,the smaller size of the hot-zone and the selective lateral induction coil system lead to an optimal control of the thermal instabilities into the silicon melt,increasing the ingot quality.In fact,the lateral induction coil system is equipped with independent turns connections and it can be used to force selectively-at different vertical positions-the most suitable thermal condition.In this way,one is able to compensate the radiative thermal losses and create a 'virtual' adiabatic wall,producing a planar solidification front or modeling the radial thermal gradient in order to obtain the desired solidification front shapes.In previous papers,the authors have presented some preliminary results obtained with a iDSS furnace^([4][5][6]).In the present paper is proposed a discussion about the numerical analysis of Mono-Like-Casting process with iDSS furnace capacity up to 120 kg of silicon feedstock.The furnace is actually under construction in the context of research activities of PFV(Polo Fotovoltaico Veneto).
