Quantitative analysis of spatially resolved electroluminescence of Cu(In,Ga)Se2 and a-Si:H thin-film solar cells and modules

Electroluminescence (EL) is the reciprocal process of the standard operational mode of a solar cell. EL imaging technique allows a fast detection of defects in solar cells and modules with low noise and high resolution. Recently, EL has become one of the most commonly used characterization tools for photovoltaic devices. There has been a significant amount of research into the interpretation and analysis of EL of silicon wafers, solar cells and modules, but very little, to date, on thin-film solar technologies. This work presents a number of varied applications of EL imaging to the analysis of both industrially produced copper indium gallium diselenide Cu(In, Ga)Se2 (CIGS), and in-house produced hydrogenated amorphous silicon (a-Si: H) thin-film solar cells and modules. The quantitative interpretation of the EL intensity and spectrum is based on the reciprocity theorem, which relates the EL emission with the external photovoltaic quantum efficiency of the device. In this work, this theorem is validated for industrially produced CIGS solar cells using spectrally resolved EL and photoluminescence (PL). The validation shows that PL and EL emission obeys a linear superposition in a limited range of the applied bias or illumination.