Degradation of copper‐plated silicon solar cells with damp heat stress

Abstract

Crystalline silicon solar cells with copper-plated contacts are fabricated, encapsulated in ethylene-vinyl acetate (EVA), and subject to extended damp heat stress (85 C and 85% relative humidity). We source cell precursors from several different cell manufacturers and employ several different patterning methods of the silicon nitride layer and deposit a plated front contact stack of nickel, copper, and tin using light-induced plating. Across different Cu-plated samples, we find similar degradation that impacts

Copper Outdiffusion from Copper-Plated Solar Cell Contacts during Damp Heat Exposure

“…The surface concentration of Cu shown in Figure is higher in the Cu-plated, EVA-encapsulated sample than in the Cu-plated, POE-encapsulated sample. We have previously reported that the diode degradation was greater in EVA-encapsulated samples than in POE-encapsulated samples, and we now suggest the reason is because Cu ingress is greater EVA-encapsulated samples.…”

“…The signal is normalized to the maximum detected signal. Lines represent the mean of multiple measurements from a sample, and shaded We have previously reported that the diode degradation was greater in EVA-encapsulated samples than in POE-encapsulated samples, 20 and we now suggest the reason is because Cu ingress is greater EVA-encapsulated samples.…”

“…22 In the first study, the degradation was not observed in sister samples with Agscreenprinted contacts, and degradation was prevented in Cuplated cells when the encapsulant was polyolefin elastomer (POE) rather than the more common ethylene vinyl acetate (EVA). 20 In the second study, degradation seemed to correlate with the average adhesion strength of the Cu-plated fingers to Si, and it was proposed that weaker finger adhesion resulted in finger dislodgement during DH testing, thereby opening a pathway for mobile Cu to diffuse into Si. 21 In the present work, we examine samples from those previous studies that exhibited pFF loss after DH stress.…”

“…In previous work, we have shown that encapsulated cells with Cu-plated contacts degrade more under damp heat (DH) stress than comparative encapsulated cells with Ag-screenprinted contacts. , Specifically, the degradation in Cu-plated samples affected diode parameters, indicating junction degradation described by increasing nonideal recombination current density ( J 02 ) and decreasing pseudo fill factor (pFF) as measured using the Suns- V OC technique . In the first study, the degradation was not observed in sister samples with Ag-screenprinted contacts, and degradation was prevented in Cu-plated cells when the encapsulant was polyolefin elastomer (POE) rather than the more common ethylene vinyl acetate (EVA) . In the second study, degradation seemed to correlate with the average adhesion strength of the Cu-plated fingers to Si, and it was proposed that weaker finger adhesion resulted in finger dislodgement during DH testing, thereby opening a pathway for mobile Cu to diffuse into Si …”

Environmental and Circular Economy Implications of Solar Energy in a Decarbonized U.S. Grid

“…80 The use of recyclable materials in the PV module can enhance recyclability at EOL and decrease landfilling. 81 Substituting abundant materials for constrained materials (e.g., copper metallization replacing silver metallization) 82 can decrease the cost of manufacturing PV systems. 44 Replacing hazardous materials in the PV module can decrease the environmental and human health risks during the use and EOL stages.…”