Polarization-Type Potential-Induced Degradation in Front-Emitter p-Type and n-Type Crystalline Silicon Solar Cells

Abstract

For SiO 2 layers underneath the SiN x antireflection/passivation layers of front-emitter p-type c-Si solar cells, this paper presents an investigation into their effects on polarization-type potential-induced degradation (PID), in addition to a comparison of polarization-type PID behavior in front-emitter p-type c-Si cells and front-emitter ntype c-Si cells. After PID tests with a bias of +1000 V, p-type c-Si cells without SiO 2 layers underneath the SiN x layers showed no degradation, although p-type c-Si cells with approx. 10 nm thick SiO 2 layers showed polarization-type PID, which is characterized by a reduction of the short-circuit current density and the open-circuit voltage. This result implies that highly insulating layers such as SiO 2 layers play an important role in the occurrence of polarization-type PID. Comparison of polarizationtype PID in p-type and n-type c-Si cells with SiO 2 layers indicated that degradation in the n-type cells is greater and saturates in a shorter time than in the p-type cells. This result is consistent with an earlier proposed model based on the assumption that polarization-type PID is caused by charge accumulation at K centers in SiN x layers. The findings described herein are crucially important for elucidating polarization-type PID and verifying the degradation model.

Mechanistic Understanding of Polarization‐Type Potential‐Induced Degradation in Crystalline‐Silicon Photovoltaic Cell Modules

“…Effects of SiO 2 layers underneath SiN x on polarization‐type PID have been investigated. [ 30–32,34,35 ] These reports indicate that SiO 2 layers play important roles in generating polarization‐type PID. We have proposed that SiO 2 layers underneath SiN x play a role in retaining excess accumulated charges at K centers.…”

“…[ 44 ] Since the publication of our earlier work, [ 23,26 ] many results that support our hypothesis have been reported. [ 30,31,34,35 ] Jonai et al reported that Al‐BSF cells, which basically have no intentional SiO 2 layers under SiN x , show polarization‐type PID when SiO 2 is inserted between SiN x and n‐type emitters. [ 30,35 ] Suzuki et al [ 31 ] demonstrated that n‐type PERT cells without SiO 2 layers exhibit no polarization‐type PID.…”

“…[ 30,31,34,35 ] Jonai et al reported that Al‐BSF cells, which basically have no intentional SiO 2 layers under SiN x , show polarization‐type PID when SiO 2 is inserted between SiN x and n‐type emitters. [ 30,35 ] Suzuki et al [ 31 ] demonstrated that n‐type PERT cells without SiO 2 layers exhibit no polarization‐type PID. It is noteworthy that the n‐type PERT cells without SiO 2 layers show low initial performance.…”

“…We have reported that the time necessary for polarization‐type PID to saturate is longer on the n‐type surface than on the p‐type surface ( Figure ). [ 35 ] In fact, in Figure 8, the labeled “n‐type” and “p‐type” have, respectively, p‐type and n‐type front surfaces. Here, “n‐type” and “p‐type”, respectively, represent the behaviors of degradation on the p‐type and n‐type surfaces.…”

“…Reproduced under the terms of the CC‐BY 4.0 license. [ 35 ] Copyright 2022, The Authors. Published by The American Chemical Society.…”