Investigation Of Liquid Phase Deposited SiO₂ Film In Silicon Solar Cells

Surface passivation plays a key role in high efficient solar cells.Nowadays,the common passivation techniques used in photovoltaic industry include plasma enhanced chemical vapor deposited SiNX（PECVD-SiNX）,atomic layer deposited Al2O3（ALD-Al2O3）,thermal grown Si02,etc.Despite their excellent passivation performances on silicon solar cells,expensive equipments are required.And the growth rate of both ALD-Al2O3 and thermal grown SiO₂ is slow.In this study,we prepared SiO₂ film by liquid phase deposition method.Compared with the method of thermal grown Si02,the liquid phase deposition has many advantages such as simple operation,low growth temperature,high deposition rate.The liquid phase deposited Si02 film proves to be uniform and dense,high-coverage with substrate.We found that the growth parameters of liquid phase deposited Si02 include the concentration of H2SiF6,the deposition time and deposition temperature have great influence on the growth rate of the film,and the deposition temperature also influenced the density of the Si02 film.Meanwhile,we systematically investigated the passivation effect of liquid phase deposited SiO₂ film on silicon wafers.The passivation quality of as-deposited liquid phase deposited SiO₂ film is quite poor,but can be dramatically improved after annealing.By analysing the minority carrier lifetime and surface recombination velocity of n-type and p-type silicon wafers passivated by liquid phase deposited SiO₂ film,we found that the chemical passivation and field-effect passivation mechanisms both exist.Although deposition parameters have little effect on the effect of passivation,we shall still carefully choose the appropriate deposition parameters.In consideration of deposition rate and preparation cost,we chose the H2SiF6 concentration of 1.5M and a deposition temperature of 50℃ as the optimal deposition parameters.Eventually,we have applied liquid phase deposited SiO₂ film as the surface passivation layer to both p-type and n-type large area solar cells,achieved conversion efficiencies of 19.5%and 19.06%,respectively.