Progression of rapid potential-induced degradation of n-type single-crystalline silicon photovoltaic modules

Abstract

This study addresses progression of potential-induced degradation (PID) of photovoltaic modules using n-type single-crystalline silicon cells. In a PID test in which a voltage of −1000 V was applied to the cells, the modules started to degrade within 10 s and the degradation saturated within 120 s, suggesting that PID is caused by positive charge accumulation in the front passivation films. We propose that these positive charges originate from positively charged K centers formed by extracting electrons from the K centers, which explains the rapid degradation and its saturation behavior. We obtain simulated and experimental results supporting this hypothesis.

Comprehensive study of potential‐induced degradation in silicon heterojunction photovoltaic cell modules

“…It has been reported that various kinds of PV cells, such as conventional p-type c-Si, [10][11][12][13][14] n-type front-emitter c-Si, [15][16][17][18][19] n-type rear-emitter c-Si, 19,20 n-type IBC c-Si, 22 a-Si thin-film, 24,25 CIGS thinfilm, [26][27][28] and CdTe thin-film 28,29 PV cells, undergo PID under negative bias. Herein, we first clarified how the J-V, EQE, and EL characteristics of SHJ PV modules change upon applying a negative bias.…”

“…In one noteworthy case, the EQE was reduced by at least half at short wavelengths (see the line "−2000 V, 21 days" in Figure 2). It has been reported that PID in many types of PV modules including p-type c-Si, 10 n-type front-emitter c-Si, 15,16,19 and CIGS 27 modules can be recovered by applying the opposite bias to that used in the degradation tests. To investigate whether such a regeneration effect occurs for the PID in SHJ PV modules, we applied a positive bias of +1000 V to a degraded module.…”

“…PID is a type of performance deterioration that is triggered by the difference in the electric potential between the grounded frame and the cells and is found mainly in large-scale PV systems, as the system bias in such installations is very high. PID reportedly occurs in numerous different kinds of PV modules fabricated from conventional p-type c-Si cells [10][11][12][13][14] ; conventional n-type c-Si cells [15][16][17][18][19] ; n-type c-Si cells with rear-side emitters 19,20 ; n-type IBC cells, 21,22 including those with front floating emitters 23 ; thin-film a-Si cells 24,25 ; copper indium gallium selenide (CIGS) thin-film cells [26][27][28] ; and cadmium telluride (CdTe) thin-film cells. 28,29 Since the degradation behavior of PV modules is known to strongly depend on their cell and module structures, PID should be investigated for each type of PV module.…”

Potential‐induced degradation in photovoltaic modules composed of interdigitated back contact solar cells in photovoltaic systems under actual operating conditions

“…14,15,[24][25][26][27][28][29] The PID-p in n-type IBC solar cells occurs under positive potential conditions, 9,[30][31][32] whereas the PID-p in n-type solar cells with a front p + emitter is observed under negative potential conditions. 14,15,[24][25][26][27][28][29] Both can be explained by the surface recombination of minority carriers arising from the charge fixed on the silicon dangling bonds back-bonded with nitrogen, known as "K centers," in the SiN x ARC layer. 9,24,25 If the ARC of p-type c-Si solar cells is constructed by the SiN x stacked on SiO 2 layers, PID-p can occur even in the p-type c-Si solar cells by applying a high positive voltage.…”

Effect of light irradiation during potential-induced degradation tests for p-type crystalline Si photovoltaic modules

“…If the encapsulant with a relatively low volume resistivity on the order of 10 14 Ω cm, such as ethylene-vinyl acetate (EVA), is used, leakage current flows from the Al frame to the PV cells accompanied by a drift of Na from the cover glass to the PV cell. Such Na drift by a high electric field and migration to the pn junction in the PV cells are one of the possible origins of PID for p-type crystalline Si PV modules, [4][5][6][7] although PID is merely a generic name for the degradation induced by the potential difference between the Al frame and the PV cells, and the degradation behavior and mechanism of PID are essentially different for different types of PV cells: for p-type crystalline Si, 1,2,7,8) possibly due to the migration of Na; for n-type crystalline Si, [9][10][11][12] possibly due to charge recombination; for Si heterojunction, 13,14) due to the reduction of transparent conductive oxide (TCO) layer; thin-film Si, 15) due to the delamination of the TCO layer, Cu(In,Ga)Se 2 , 16,17) CdTe, 18) and others. Such mechanisms are still controversial in spite of much effort using various kinds of tools and techniques devoted to clarifying the main origins of PID.…”