Light Induced Degradation (LID)

 

LID test is performed on modules to assess stability of performance in response to light exposure.

Qualification for c-Si modules requires 5 hours of preconditioning at 1000 W/m2 prior to power output measurement due to the known ~4% power output degradation in B-doped Cz-Si cells during first 5 hours of light soaking which recovers upon anneal or dark storage due to activation of metastable boronoxygen defect which lowers carrier lifetime which is greatly reduced using either Ga-doped Cz-Si or low oxygen content B-Cz-Si.
Light soaking stabilization required in IEC 61646 for thin film was derived due to the reduction in dark conductivity and photoconductivity of a-Si:H after light exposure

Recombination-induced breaking of weak Si-Si bonds by optically excited carriers after thermalization, producing defect centers that lower carrier lifetime - according to Staebler-Wronski Effect