Efficiency enhancement of bifacial PERC solar cells with laser-doped selective emitter and double-screen-printed Al grid

We report that the application of a laser-doped selective emitter (SE) can improve the trade-off between the recombination in the emitter and the Ag-Si specific contact resistance and that a double-screen-printed rear aluminum grid can decrease the series resistance in the industrial bifacial passivated emitter and rear cell (PERC). Our results reveal that a front-side efficiency of 21.9% can be achieved in the PERC (SE)+ solar cell by using low surface-recombination Al2O3/SiNx films as passivation layers, low-recombination emitter, and low resistive Ag-Si contact with an optimized sheet resistance of the lightly doped area of SE with 125 Omega/sq and sheet resistance of the highly doped area of SE with 70 Omega/sq. The highest front-side efficiency of 22.0%, with open-circuit voltage of 680mV, short-circuit current density of 40.1mA/cm(2), and fill factors of 80.8%, is obtained by using double-screen-printed rear Al grid process, which is 0.1% higher than the best PERC (SE)+ solar cell. The rear-side double-layer antireflection coating consists of 50nm SiNx:H (n = 2.1) and 10 nm SiNx:H (n = 2.37), which enables a large bifacial gain with the output power density P-MPP of 25.5mW/cm(2) in the PERC (SE)+ solar cell by using double-screen-printed rear Al grid process when rear-side illumination intensity E-rear = 0.25 suns.