Photovoltaic cells can convert sunlight into electricity, but not all the energy of solar radiation can be converted into electricity, a part is always converted into electricity, and the other part is consumed, and a small part is converted into electricity, which is consumed. is a large part. Various photovoltaic cells are also different, some photovoltaic cells convert more parts into electricity, and some less. Therefore, conversion efficiency has become a very important criterion for measuring photovoltaic cells.

The energy conversion efficiency of a photovoltaic cell is the ratio of the electrical energy output from the terminals of the photovoltaic cell to the input solar radiation energy, expressed as a percentage. That is to say, the conversion efficiency η can be calculated by the following formula:

η= (P_{m}/P_{i})×100%

In the formula, η is the conversion efficiency of the photovoltaic cell; P_{m} is the output power of the photovoltaic cell; P_{i} is the solar radiation energy entering the photovoltaic cell.

The output power of photovoltaic cells is affected not only by the intensity of solar radiation, but also by temperature and environmental conditions. In order to make the calculated energy conversion efficiencies of photovoltaic cells comparable, a standard test condition for ground-mounted photovoltaic cells, or STC for short, has been developed.

①The solar spectrum distribution when the atmospheric mass is AM1.5.

②The solar radiation intensity is 1000W/m².

③The temperature is (25±1)℃.

The conversion efficiency measured under STC conditions is the standard conversion efficiency, or peak wattage.