Influence of soiling layer on quantum efficiency and spectral reflectance on crystalline silicon PV modules

Reduction in transmittance of glass superstrate due to soiling on PV modules is studied by various groups throughout the world. However, the soil layer changes not only the irradiance level but also changes the spectral distribution of the incoming solar radiation. In this work, we have selected three solar cells within a commercial module covered with different thickness of soil layer. These soiled solar cells within a module are used to study the spectral reflectance and quantum efficiency changes at various wavelengths. Heavily soiled solar cell (~74.6gm/m²) showed a very high reflectance loss and very low quantum efficiency at all wavelengths with respect to after-cleaning. The three soiled solar cells were then cleaned using three different cleaning techniques - 60psi compressed air clean, brush assisted 30psi compressed air clean and water cleaned. Short circuit current, spectral reflectance´s and quantum efficiency´s dependence on wavelengths is studied before and after each cleaning steps.