Direct-PECVD a-SiOx：H/a-SiNx：H叠层系统对多晶硅电池的钝化研究

Investigation on mc-Si Passivation Using Direct-PECVD a-SiO_x:H/a-SiN_x:H Stack System

本文中应用全部PECVD工艺沉积a-SiOx:H、a-SiNx:H,和a-SiOx:H/a-SiNx:H叠层系统,比较了不同钝化膜对多晶硅太阳能电池发射极和背面钝化效果,应用FGA、RTP等热处理方法对钝化膜进行处理,重点讨论了FGA(Forming gas annealing)温度和时间的长短对钝化的影响。结果表明:低温FGA对只有单面钝化膜的硅片钝化效果不明显,而在800℃下FGA有明显作用,而且钝化效果随着时间的增加呈现出先增大后减小然后再增大的现象;退火后降温环境中是否有H和降温时间对钝化效果有很大的影响,但是对于双面膜无论FGA温度高低对钝化都有帮助,文中对上述现象做了合理的解释。最后利用双面叠层钝化膜经过FGA处理后得到的多晶硅片的少子寿命达到14.2μs,比镀膜之前的3.0μs提高了11.2μs,使多晶硅太阳能电池暗电压Voc达到630mV。

a-SiOx：H, a-SiNx：H and a-SiOx：H/a-SiNx：H stack system for mc-Si passivation thin films all deposited using direct PECVD. FGA and RTP were used to treat the as-grown passivation films and the temperature and process time of the FGA were investigated. For single side deposition, we found we couldn＇t get improvement on minority carrier lifetime under whatever processing time if low temperature FGA was used. But did works for double side deposition. Also we found the lifetime showed increasing-decreasing-increasing format versus the FGA time at 800 ℃. Moreover, whether there exists H during the cooling process followed the annealing is very important. Longer cooling time is good to passivation for single side deposition wafers. But for double side deposition, both low temperature and high temperature are beneficial to the passivation. Appropriate explanations for these results were given in this paper. A long lifetime as high as 14.2 μs was obtained with this method. It increases by 11.2 μs compared to the former we get .As a result, the implied Voc of mc-Si solar cell goes up to 630 mV.