Electrical Efficiency of a Solar Cell

Abstract

Our goal was to determine the electrical efficiency of a solar cell, specifically a CuInGaSe2 solar cell. Solar cells work by converting energy from the sun in the form of photons to electrical energy in the form of electrons. However, the solar energy converted into electrical energy is limited by a property of solar cells called the quantum efficiency. The quantum efficiency of a solar cell is the fraction of photons hitting the cell that are converted into electrons; quantum efficiency varies as a function of wavelength. Another key component which also varies as a function of wavelength is spectral irradiance, i.e. the power per square meter of a photon. The electrical efficiency of a solar cell is the ratio of the energy produced by the cell over the energy that would be produced if the cell absorbed all of the energy in each photon. To determine this ratio, data from a spreadsheet providing the spectral irradiance for solar radiation reaching the Earth’s surface was used to find the energy a cell would produce if it absorbed all of the sun’s energy. This data was then combined with the cell’s unique quantum efficiency data to determine the energy that the solar cell would actually produce which was then used to determine the electrical efficiency.