Dependence of the Optimization of the Front Grid Design in Passivated Emitter and Rear Contact c-Si Solar Cells on the Finger Width and the Aspect Ratio

Abstract

In this research, modeling was performed to optimize the grid of the front surface of a solar cell with the passivated emitter and rear contact (PERC) structure by considering the recombination characteristics. The front surface recombination velocity can be reduced in two main ways. The first method is to reduce the emitter Auger recombination by lowering the surface doping concentration during emitter formation, and the second method is to reduce the recombination that occurs at the surface when the electrode and the silicon are in contact, which is called metal-induced recombination and is represented by J(0.metal). Because J(0.metal) increases in proportion to the area of the front electrode, minimizing the finger width and number by optimizing the electrode design is important. Therefore, the front electrode grid should be designed considering the emitter characteristics, J(0.metal), according to the number of fingers and the resistance. In this research, the front grid of the solar cell was optimized via modeling using equations to calculate the number of fingers and the resistance. According to the finger width, the number of busbars, the sheet resistance, the aspect ratio, and the number of fingers corresponding to the maximum efficiency were identified. As a result, this modeling enabled us to optimize the front grid to the desired conditions, and we found that an increase in the number of busbars plays an important role in improving the efficiency of solar cells. In addition, the efficiency change with increasing number of busbars can be seen to be affected by the width of the finger and the resolution of the printed finger rather than the aspect ratio.