The fill factor is also called the curve factor and is represented by FF. The fill factor refers to the ratio of the shaded rectangular area (ImVm) to the dashed rectangular area (IscVoc) in Figure 1, that is, the ratio of the peak output power of the photovoltaic cell to the product of the open-circuit voltage and short-circuit current:

FF=Pm/IscVoc

The fill factor is a unitless quantity and is an important parameter to evaluate and measure the output characteristics of photovoltaic cells. It can reflect the quality of solar cells. The higher the value, the more rectangular the output characteristics of photovoltaic cells are. higher photoelectric conversion efficiency.

The value of the fill factor is less than 1, generally 0.6~0.8, and it can also be expressed as a percentage. Fill factors greater than 0.7 indicate good quality components. Fill factor is an important parameter to judge the quality of solar cell modules. The relationship between the fill factor and the photoelectric conversion efficiency of a photovoltaic cell is:

η=IscVocFF/EA

In the formula, η is the photoelectric conversion efficiency of the photovoltaic cell; E is the light intensity; A is the area of the photovoltaic cell.

Both series resistance and parallel resistance of photovoltaic cell modules affect the fill factor. The smaller the series resistance of the photovoltaic cell, the larger the parallel resistance, and the larger the fill factor, which is reflected in the current-voltage characteristic curve of the solar cell. The curve is closer to a square, and the conversion efficiency of the solar cell is higher at this time.