5. Light trapping techniques
Different materials have different spectral range. For example, for crystalline Si (c-Si) solar cell, the spectral range is 600–1100 nm and for amorphous Si (a-Si), the spectral range is 600–800 nm. A large part of the long wavelength incident photons are not absorbed, which reduces the efficiency. Charge carriers generated far away from the p–n junction are also not effectively collected, owing to bulk recombination. To reduce these losses or to reduce the light induced degradation and minimize the process time, absorption layer thickness should be as low as possible. There are many techniques which are used for improving the efficiency of solar cell including various light trapping techniques. By using antireflection coating and nanotechnology based methods, efficiency can be enhanced. Various nanoparticles are used which scatter light in various modes or internally reflect light in multiple modes so that the optical path for absorption is much larger than the film thickness. Various light trapping techniques are discussed below.
These losses affect the efficiency of thin film solar cell; therefore it is necessary to reduce these losses in order to increase the efficiency of the solar cell. Various methods used for reducing these losses are discussed below.