Non-destructive infrared optoelectronic lock-in carrierography of mc-Si solar cells

Abstract

A novel non-destructive, non-contact laser-induced infrared lock-in carrierographic imaging technique based on photocarrier radiometry (PCR) was introduced to characterize industrial multi-crystalline silicon solar cells. The modulated photovoltage (MPV) was measured simultaneously with the PCR signal in point-by-point imaging using focused laser scanning. The PCR and MPV signals were also investigated as functions of modulation frequency and load resistance at fixed coordinate points in order to better understand and interpret the physical optoelectronic origins of the carrierographic imaging contrast. A InGaAs-camera based carrierograhic lock-in imaging technique with a spread laser-beam illumination of solar cells was also introduced and was shown to exhibit contrast based on p-n junction RC time constants and on quasi-neutral bulk minority carrier recombination lifetimes.