Verification of power loss mechanisms contributing to the illuminated lock-in thermography (ILIT) signal

Illuminated Lock-In Thermography (ILIT) is a versatile tool for spatially resolved detection of power losses in silicon solar cells close to real operation conditions. In this paper, quantitative analysis of different power loss mechanisms contributing to the ILIT-signal will be presented by means of ILIT-measurements. First, the appearance of heat due to energy losses of free carriers after photon absorption and energy losses of carriers crossing the p-n-junction will be verified in ILIT-measurements. Further, two different methods of quantifying ohmic type shunts with ILIT-measurements will be compared. It will be shown, that it is possible to determine a reliable global value for the parallel resistance with ILIT under certain assumptions. At last, an assumption used for the determination of shunt resistances with ILIT is checked.