Study On Fabrication And Property Of Ultrathin Monocrystalline Silicon Solar Cells

Monocrystalline silicon solar cells have been dominating the photovoltaic?PV?market for many years.The thickness of commercial monocrystalline silicon solar cells is usually around 180?m,which is not suitable for certain occasions such as solar aircraft and curved roofs.However,ultra-thin monocrystalline silicon solar cells are lightweight,flexible,and highly efficient,and have great application prospects in these special occasions.The cost of silicon wafers accounts for 40%of the cost of monocrystalline silicon solar cells,and reducing the thickness of the silicon wafer also reduces the manufacturing cost of the monocrystalline silicon solar cells.Due to the difficulty in the preparation of ultra-thin monocrystalline silicon materials,and the existing monocrystalline silicon solar cell preparation process is not suitable for the preparation of ultra-thin monocrystalline silicon solar cells,the ultra-thin monocrystalline silicon solar cells have not fully showed their application potential.Therefore,it is imperative to find a suitable preparation method of ultra-thin monocrystalline silicon and an ultra-thin monocrystalline silicon solar cell preparation process.Thinning method is the main method for preparing ultra-thin monocrystalline silicon materials.However,the thinning rate of the conventional alkali thinning method is slow,which seriously affects the production efficiency.In this thesis,the conventional bulk monocrystalline silicon wafer was etched by the mixed solution of AgNO₃,H₂O₂ and HF.The rapid preparation of ultrathin monocrystalline silicon material at room temperature was successfully achieved,and the thinning rate was improved nearly 10 times,compared with the conventional high temperature alkali etching process.The effects of silver ion concentration and?=[HF/?HF+H₂O₂?]value on the silicon etching rate,surface morphology and reflectance were systematically studied in this thesis,and the reaction mechanism of silver assisted chemical etching was analyzed according to the experimental phenomena and results.On this basis,ultra-thin monocrystalline silicon solar cells with different thicknesses of 40?m,55?m and 70?m were prepared,and the conversion efficiency of the solar cells reached 11.3%,11.9%and 12.4%,respectively.The effect of thickness on the performance of ultra-thin monocrystalline silicon solar cells was simulated by PC1D simulation software.The results showed that the conversion efficiency of solar cells decreases with the decrease of thickness,which is consistent with the experimental results.Passivated emitter and rear cell?PERC?has higher conversion efficiency than conventional aluminum back-field solar cell.Here,in order to improve the conversion efficiency of ultra-thin monocrystalline silicon solar cells,a microsphere-assisted opening process was used to replace the traditional laser grooving process and the ultra-thin monocrystalline PERC solar cells were successfully fabricated.The effects of spin coating speed and spin coating concentration on the back coverage of polystyrene microspheres on the back side of the cells were studied.On this basis,ultra-thin monocrystalline PERC solar cells with different thicknesses of 40?m,55?m and 70?m were fabricated,of which the conversion efficiencies of 13.6%,13.9%and 14.1%were obtained respectively.Three as-fabricated ultra-thin solar cells exhibited good flexibility.After 200 times cyclic bending,the conversion efficiency was only relatively reduced by 9.56%,5.04%,and 4.26%,respectively.In view of the low conversion efficiency of the prepared ultra-thin monocrystallinel silicon solar cells,PC1D simulation software was used to study the effects of surface recombination rate,and doping concentration and junction depth on the output characteristics of the solar cell.The simulation results showed that the best positive recombination rate was 10³ cm/s,the best back recombination rate was 10³ cm/s,the optimal doping concentration of the emitter is 10¹⁹ cm^-3,and the optimal junction depth was 0.1?m.The 40?m thick ultra-thin monocrystalline silicon solar cell had a conversion efficiency of up to 20.15%.The simulation results provided a reliable reference for the preparation of highly efficient ultra-thin monocrystalline silicon solar cells.