Influence of Impurities in Module Packaging on Potential-Induced Degradation

Abstract

Chemical compounds were added into crystalline silicon cell mini modules, including in the encapsulant, interfaces, and glass, to determine their effect on potential-induced degradation (PID). Fe, either in the glass or at the glass/encapsulant interface, was found to be correlated with increased PID, but the difference in module power loss was not statistically significant compared to controls. Additions of Cu, Cr, Pb, Sn, Ag, and Na compounds to either the encapsulant or at the glass/encapsulant interface did not appear correlated with PID. Lock-in thermography on bare cells affected by PID removed from the mini modules show highly localized areas of junction breakdown, and SIMS analysis indicates localized impurities as well, though a spatial relation between the two was not established. Deposition of a conductive layer on the front surface of the cell, either with semitransparent Ta or Poly 3,4-ethylenedioxythiophene (PEDOT), eliminated PID when the cells were stressed at -1000 V bias, 50°C, with the glass face grounded for 140 h.

Sodium Outdiffusion from Stacking Faults as Root Cause for the Recovery Process of Potential-induced Degradation (PID)

“…If the modules/cells are not resistant to PID, the degradation mechanism can result in yield losses of 20 percent or more within a period of one year. According to recent publications, the PID shunting effect (PID-s), which decreases strongly the parallel resistance RP of the modules, is the most relevant type of PID [4,5]. However, it has also been shown that PID-s can influence the recombination behavior of the solar-cell [4,6].…”

Development of an IEC test for crystalline silicon modules to qualify their resistance to system voltage stress

“…Sodium has also been found in high concentrations in stacking faults penetrating the junction . It has also been speculated that ions accelerated over an insulating dielectric or antireflective coating under an electric field may imbed in and damage the junction . Corona discharge over cells has been found to induce PID‐like junction failure .…”

In-Situ Measurement of Crystalline Silicon Modules Undergoing Potential-Induced Degradation in Damp Heat Stress Testing for Estimation of Low-Light Power Performance

“…Sodium has also been found in high concentrations in stacking faults penetrating the junction [5]. It has also been speculated that ions accelerated over an insulating dielectric or antireflective coating under an electric field may embed and damage the junction [6] in view that corona discharge over cells has been found to induce PID-like junction failure [7]. Considering that both reversible and irreversible components of junction failure are associated with system voltage stress [8], it is conceivable that multiple mechanisms are active.…”