1. LID (Light Induced Degradation) is a loss of performances arising in the very first hours of exposition to the sun, with Crystalline modules. It may namely affect the real performance with respect to the final factory flash tests data delivered by some PV module providers. It is unclear how it affects the performances with respect to the specified STC values. If the modules are sorted according to their final factory flash test for determining their Nominal Power class, the LID will indeed represent a loss with respect to STC. The LID loss is related to the quality of the wafer manufacturing, and may be of the order of 1% to 3% (or even more). It is due to traces of Oxygen included in the molten Silicon during the Czochralski process. Under the light exposition effect, these positive-charged O2 dimers may diffuse across the silicon lattice, and create complexes with boron dopant acceptors. The boron-oxygen complexes create their own energy levels in the silicon lattice, and can capture electrons and holes which are lost for the PV effect.
2. Crystalline p-type boron doped silicon solar cells generally exhibit a degradation of conversion efficiency during the first hours of exposure to the sun light. This light induced degradation (LID) is associated with the formation of the well known boron oxygen complex which acts as a harmful defect and reduces the minority carrier diffusion length accordingly. LID is therefore related to both, boron and oxygen concentration.
Degradation, PV losses
http://files.pvsyst.com/help/lid_loss.htm (1.); http://isc-konstanz.de/fileadmin/doc/24EU-PVSEC/KPeter.pdf (2.)
Author: Svenja Gutt