The Cause of Light-Induced Degradation (LID) in the P-type PERC Cell

The issue of Light-Induced Degradation (LID) is affecting mostly high-efficient PERC cells, but what is LID and why is affecting high-efficient PERC p-type cells mostly? 

What is Light-Induced Degradation (LID)? 

According to Openmod, LID is due to traces of oxygen included in the molten silicon during the Czochralski process. Under the light exposition effect, this positive-charged O2 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.

The syndrome of LID for PERC p-types

One of the main reasons for emerging LID in high-efficient PERC cells is the presence of boron as the dopant (impurity) in the crystalline lattice of silicon. As generally reported in scientific research journals, LID happens when PV modules with p-type PERC cells expose for the first time to sunlight in the construction phase of PV plants. Thus, p-type PERC cells face this challenge in the very first hours of exposition to the sun. 

As shown in Figure 2, power output below 100% in the first year of PV module performance is one of the symptoms of the LID. The challenge of LID for PERC solar cells is important to overcome if this technology is aimed to become mainstream in PV module manufacturing.

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Source:@ Openmod & @Solar_Edition
Photo:@ hyperphysics & @Solar_Edition
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