Research On High Resistance And Dense Emitter Solar Cell For Mass Production

High Efficiency and cost Effective silicon solar cell is the developingtrend in PV industry, lots of mass production high efficiency solar cellhave adopted the high resistance emitter, It has the advantage ofdecreasing front surface recombination, and improving surface minoritylifetime, This is the most efficient method to improve the cell efficiencywithout increase product cost. Low depth high resistance emitter hasnarrow process window and the silver paste should have special firingcurve.In this paper,our research direction is focused on the optimization onhigh resistance emitter and the following process technology.In this thesis, we focused on the process optimization of high qualitycrystalline silicon solar cell, especially on the high emitter resistance solarcell, also on how to improve the Back-End process procedure thereafter. Inthe high emitter resistance case, deep PN junction method was used. Thiswas mainly from the needs of the process reproducibility and stability. Inorder to maximize the advance of the high resistance emitter, we have donelots of experiments to optimization the passivation and compatibility.The high resistance emitter technology will cause the increase of theRs, and finally influence Fill factor and efficiency of the final cell.According to the paste and emitter contact SEM profile analysis, we couldsee that for high emitter solar cell,front contact paste have great influenceon the contact formation of the front surface, the following process have toadjust to match with the front high resistance emitter.In order to effectively decrease the contact resistance on the frontemitter, we have designed the front contact pattern; also we have done lotsof experiments on paste optimization. Based on the current production line, we have investigated the influence of the front emitter passivation bytandem SiNx thin film. All the goal is to improve the cell Voc、Isc and FFthrough front emitter optimization.In this thesis we have focus our research work on the followingprocess：1) Optimization of the front emitter;2) Optimization thepassivaation quality of front emitter and to improve the cell Voc withtandem SiNx thin layer;3)The influence of the emitter resistance on68fingers: According the experiments results, we have gotten the optimizedcell results of emitter resistance on68fingers;4) optimization theinfluence of the front cell paste under front high resistance emitter. Wehave discussed several pastes to investigate its influence;5) Optimizationthe firing profile based on the cell efficiency results. In order to match thefollowing procedure, we have to carefully control the fire temperature andtime to achieve better cell efficiency.In order to optimize the cell efficiency based on68fingers, we havedone serial experiments on how to improve the cell fire profile, thedetailed information in table5.1, and the figure5.25is the influence of thefire temperature on the cell quality. After a series of experimentaloptimization, an open circuit voltage of635mV, a short circuit current of5.817A, and an average cell efficiency18.67%have been achieved, andthese results meet our initial research goal.