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 °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.

Herein, it is demonstrated that low temperature current injection and annealing (CIA) treatment can cause evident improvements in open circuit voltage, short‐circuit current, and fill factor of tunnel oxide‐passivated contact (TOPCon) silicon solar cells, leading to a notable conversion efficiency gain (over 0.4% absolute at the best condition). The effects of injected current and annealing temperatures toward the improvement of electrical performance of the TOPCon solar cells are compared. The more evident increase in the electrical performance after the CIA treatment may come from the higher fill factor improvements, which can be induced by the change of contact resistance after the CIA treatment, the potential involvement of hydrogen is discussed. The CIA treatment can be a reliable approach to further enhance the conversion efficiency of TOPCon solar cells, which is of great significance for the global PV industry.