Impact of Micro-Cracks on the Degradation of Solar Cell Performance Based On Two-Diode Model Parameters

Electroluminescence (EL) imaging technique has become a powerful and fast characterization tool providing spatially-resolved information about electrical, optical and material properties of solar cells. When applying a forward bias the solar cell emits infrared radiation whose intensity is governed by the minority carrier lifetime in the bulk and thus decreases considerably in the vicinity of intrinsic defects and cracks. In this work the influence of micro cracks and the progression of already existing cracks in multicrystalline silicon solar cells are investigated. The impact of these defects on the electrical solar cell parameters is studied in the frame of the two-diode model. Statistically proven, it was found that beside a decrease in EL intensity the short circuit current Jsc and the efficiency η also will be reduced, whereas a strong increase in the recombination current density j02 is observed. This work on crack detection and the research on crack-forming will help to explain the reasons behind the loss of efficiency seen in long-term performance analyses