Solar cells, called "solar chips" or "photocells", are devices that directly convert light energy into electricity through the photoelectric effect or photochemical effect. To evaluate the advantages and disadvantages of solar cells, the following technical parameters need to be considered:

1. Open circuit voltage

Open circuit voltage VOC: that is, the solar cell is exposed to AM1.5 spectral conditions and 100 mW/cm2 light source intensity, and the output voltage value of the solar cell is open at both ends. The size of Voc is proportional to the logarithm of the incident spectral irradiance, and is independent of the area of the battery. When the junction temperature rises, the Voc value will decrease.

2.Short circuit current

Short-circuit current ISC: It is the current value that flows through both ends of the solar cell when the solar cell is exposed to AM1.5 spectral conditions and 100 mW/cm2 light source intensity. The Isc value is related to the area size of the solar cell, the larger the area, the larger the Isc value, for the same solar cell, the Isc value is proportional to the irradiance of the incident light, when the cell junction temperature rises, the Isc value increases slightly.

3. Maximum output power

The working voltage and current of solar cells change with the load resistance, and the working voltage and current values corresponding to different resistance values are made into curves to obtain the volt-ampere characteristic curve of solar cells. If the selected load resistance value can maximize the product of output voltage and current, the maximum output power can be obtained, which is represented by the symbol Pm. At this time, the working voltage and working current are called the best working voltage and the best working current, which are represented by the symbols Um and Im respectively.

4. Fill factor

Another important parameter for solar cells is the fill factor FF (fill factor), which is the ratio of the maximum output power to the product of the open circuit voltage and short circuit current.

FF: is an important indicator to measure the output characteristics of solar cells, is the representative of the solar cell with the best load, can output the maximum power characteristics, the greater the value of the solar cell output power. FF is always less than 1. The series and parallel resistors have great influence on the filling factor. The larger the series resistance is, the more the short circuit current drops and the more the filling factor decreases. The smaller the shunt resistance, the greater its component current, resulting in the more the open circuit voltage drops, and the more the fill factor drops accordingly.

5. Conversion efficiency

The conversion efficiency of a solar cell refers to the maximum energy conversion efficiency when the optimal load resistance is connected on the external circuit, and is equal to the ratio of the output power of the solar cell to the energy incident on the surface of the solar cell. The photoelectric conversion efficiency of solar cell is an important parameter to measure the quality and technical level of the battery, which is related to the structure of the battery, junction characteristics, material properties, working temperature, radiation damage of radioactive particles and environmental changes.