Lock-in thermography based local solar cell analysis for high efficiency monocrystalline hetero junction type solar cells

Until now the Dark Lock-in Thermography (DLIT) based "Local I-V" method for analyzing the inhomogeneity of the two-diode parameters of solar cells was applied mostly to multicrystalline silicon cells. In this contribution it is applied to three high-efficiency monocrystalline cells of the hetero junction type (HJT), one showing very good and two showing slightly degraded cell parameters. It is shown that the degradation of the lower performing cells is mainly due to additional local J02-type current contributions, which are partly stemming from surface injuries and mainly degrade the fill factor. It can be estimated that the local inhomogeneous dark current contributions, which can be imaged and quantified by DLIT, degrade the efficiency of the best cell only by 0.1%, but that of the stronger degraded cells by 0.3% and 0.6% (absolute) respectively. Under reduced illumination intensity the differences between the cells are even higher. The possibilities and limitations of the "Local I-V" evaluation of solar cells for investigating high-efficiency cells are discussed.