Study on the improvement of p-type multi-crystalline silicon material for solar cells by the hydrogenation with electron injection

In this paper, we have found that the efficiency of p-type mono-crystalline silicon (mono-Si) passivated emitter and rear contact (PERC) solar cells can be increased by $0.12{\%}_{abs.}$ with the process of hydrogenation with electron injection (HEI). However, the same scheme was not suitable for p-type multi-crystalline silicon (mc-Si) solar cells. To promote power conversion efficiency (PCE) for the mc-Si solar cells, we have explored a developed HEI process for the mc-Si solar cells to improve the device performance. Meanwhile, we also analysed the mechanization inside the solar cells after applying the HEI process. Through the design of experiment (DOE), the correlation among injection current, temperature, injection time and efficiency improvement was analysed in detail. It was proved that mc-Si solar cells require higher current injection and temperature to passivate the complex impurities in the bulk, when compared to mono-Si solar cells. With the optimal scheme explored by this paper, the open circuit voltage ($U_{oc}$), short circuit current density ($J_{sc}$) and fill factor (FF) of p-type mc-Si solar cells, respectively, increased by 1.2 mV, 0.11 mA ${\text{cm}}^{-2}$ and $0.05{\%}_{abs.}$, respectively. The efficiency was improved about $0.11\pm 0.005{\%}_{abs.}$. These results will provide a certain method and basis for further improving the efficiency of mc-Si PERC cells and overcoming the light-elevated temperature-induced degradation by HEI process.