Performance Improvement of Gallium-Doped Passivated Emitter and Rear Cells by Two-Step Bias Application

Passivated emitter and rear cell (PERC) solar cells have dominated the photovoltaic market in recent years. Continuously improving the efficiency of PERC solar cells is of great importance to enable the goal of low electricity cost, which is cheaper than the cost of thermal power generation. Herein, it is demonstrated that a two-step postfiring bias treatment is able to evidently enhance the efficiency of commercial gallium-doped PERC solar cells by up to 0.1% absolute. In detail, the first-step bias treatment is done by forward biasing the PERC solar cells at 12 A and 200 degrees C for 60 min, resulting in an average efficiency enhancement at around 0.05% absolute. The second-step bias treatment is done by reverse biasing the PERC solar cells at -0.1 or -0.2 V and at the elevated temperatures for certain times, leading to another average efficiency enhancement at around 0.05% absolute. To explore the mechanism underlying the two-step bias treatments on improving cell efficiency, a new model in light of hydrogen behavior under electric field is proposed to explain this phenomenon.

Automated summary

The two-step postfiring bias treatment can significantly enhance the efficiency of commercial gallium-doped PERC solar cells by up to 0.1%, with positive biasing followed by negative biasing resulting in an average efficiency enhancement of around 0.05% each. A new model involving hydrogen behavior under electric field is proposed to explain the mechanism behind the efficiency improvement from the bias treatments.