Silicon solar cell electrical parameter measurements through quantitative lock-in carrierographic (photoluminescence) and thermographic imaging

We demonstrate theoretically and experimentally quantitative long-pass filtered lock-in carrierography (LIC) or lock-in photoluminescence (LIP) imaging and perform comparisons with lock-in thermography (LIT) imaging of industrial Si solar cells. Optoelectronic LIP and thermoelectronic LIT imaging modalities are used for non-destructive, non-contact measurements of the electrical parameters of solar cells from images obtained at various external load resistances. It is shown that quantitative surface-averaged pixel brightness statistical distributions derived from near-infrared (NIR) LIP and mid-infrared LIT images can be used to measure, among other parameters, photogeneration current density, diode saturation current density, ideality factor, and maximum power photovoltage of a multi-crystalline Si solar cell. LIP images were found to have superior contrast and spatial resolution to the respective LIT images. The electrical parameter values measured from the images were found to be in very good agreement with each other and with electrical measurements (EM). The theory further allows for the generation of derivative diode saturation current density and ideality factor images.