Investigation On Surface Oxidation Of Multicrystalline Silicon Using Atmospheric Pressure Plasma Jet And Liquid Oxidation Method

In silicon-based solar cell modules,the potential induced degradation(PID),which caused by sodium ions' drifting from glass to silicon cell,has led to large power and economic losses.An important way of solving PID issue is to prepare a dense silicon oxide film on the silicon surface,in order to play a role in blocking the path of sodium ions.Some researchers have proposed a method to deposit a layer of silicon oxide by using plasma enhanced chemical vapor deposition(PECVD),but the films prepared by this method is not dense enough to be used in solving PID issue,and the deposited films also showed problems in adhesion.Other preparation methods,such as thermal oxidation,light induced anodic oxidation and ozone oxidation,are also suggested.Researchers have used these methods to directly oxidize the top layer of silicon as an alternative way of PECVD,but there are still some problems in film thickness controlling and environmental protection etc..In view of this,this paper is devoted to the development of two convenient and environmentally friendly silicon surface oxidation techniques,the first one is atmospheric pressure plasma jet(APPJ)device which based on the widely used APPJ technology,the second is liquid oxidation device which based on the chemical reaction under the participation of noble metal oxide coated titanium anode.The effect of silicon surface oxidation and anti PID ability were tested and analyzed.For the atmospheric pressure plasma jet device,the experimental results show that: 1.Compared to the 20 kHz-driven APPJ,the 2.0 MHz-driven one has better temporal continuity,higher power utilization rate,higher electron density and active particle density.Hence,2.0 MHz RF power was used for mc-silicon surface oxidation experiments.2.After APPJ treatment,the results of contact angles,XPS,and TEM image all show that the surface of mc-silicon is oxidized,and the oxidation process does not shorten the minority carrier lifetime.For the liquid oxidation device,the experimental results show that: 1.Mc-silicon surface has stronger hydrophilicity after treated by liquid oxidation in the electrolyte contained chloride ions.The results of XPS and TEM image confirm that the change of hydrophilicity is caused by surface oxidation.2.Using HCl solution as electrolyte,the liquid oxidation step was placed in the process of multicrystalline silicon solar cells,solar cells were produced and then packaged into modules.It is found that these cells and modules have similar electrical properties as the ozone oxidized ones,while the liquid oxidized modules have better anti-PID abilities for their power decay is lower than the ozone oxidized module.The above research results show that the two technologies we developed both have certain potential in the application of anti-PID.On the one hand,the 2.0 MHz-driven APPJ can oxidize silicon surface rapidly without damage.On the other hand,liquid oxidation method can be well-integrated into the multicrystalline silicon solar cell process,solar cell modules prepared by this method has excellent anti-PID ability.The investigations have some guiding significance for the research and application of anti-PID.