Faculty of Engineering School of Photovoltaic and Renewable Energy Engineering Advanced Hydrogenation Group SPREE Alumni End of Year Event, 30 th November 2017 UNSW Sydney “PV module degradation: the impact of light induced degradation (LID) and how to fix it!” Dr. Alison Ciesla Other contributors: Catherine Chan, Ran Chen, Tsun Fung, Daniel Chen, Moonyong Kim, Brett Hallam, Chendany Sen, Utkarshaa Varshney, Carlos Vargas, Ziv Hameiri, Kyung Kim, Shaoyang Liu, Aref Samadi, Bruno Stefani, Iskra Zafirovska, Malcolm Abbott, CheeMun Chong, Stuart Wenham
Background & Outline
Background & Outline • LID in Cz mono modules due to BO defect C.R. Osterwald, A. Anderberg, S. Rummel, & L. Ottoson , ‘Degradation Analysis of Weathered Crystalline-Silicon PV Modules’ PVSC 2002
Background & Outline • LID in Cz mono modules due to BO defect Typically 2-5% absolute power loss in the first 50 h in the sun!
Background & Outline Hydrogen is • LID in Cz mono modules due to BO defect the solution!
Background & Outline • LID in Cz mono modules due to BO defect – solutions! • LID in multi-PERC ??
Background & Outline • LID in Cz mono modules due to BO defect • LID in multi-PERC ?? Kersten et al. ‘Degradation of multicrystalline silicon solar cells and modules after illumination at elevated temperature’ SOLMAT vol.142, 2015
Background & Outline • LID in Cz mono modules due to BO defect – solutions! • LID in multi-PERC ?? • Not the only issue with multi...
Background & Outline • LID in Cz mono modules due to BO defect – solutions! • LID in multi-PERC ?? • Not the only issue with multi... 3 Key issues: Incompatibility with diamond wire sawing due to texturing challenges
Background & Outline • LID in Cz mono modules due to BO defect – solutions! • LID in multi-PERC ?? • Not the only issue with multi... 3 Key issues: Incompatibility with diamond wire sawing due to texturing challenges Poorer wafer quality preventing full benefit of PERC design K. Petter et al. (Hanwha Q-Cells) presented at 9th International Workshop on Crystalline Silicon for Solar Cell, Tempe Arizona, October 2016
Background & Outline • LID in Cz mono modules due to BO defect – solutions! • LID in multi-PERC ?? • Not the only issue with multi... 1 3 Key issues: 0 Incompatibility with diamond wire sawing Relative change in V oc (%) -1 due to texturing challenges -2 Poorer wafer quality preventing full benefit -3 of PERC design -4 Severe LID -5 -6 0 200 400 600 800 1000 1200 1400 Light soak time at 70 °C, 0.46 kW/m 2 (hours)
Background & Outline • LID in Cz mono modules due to BO defect – solutions! • LID in multi-PERC ?? Up to 16% relative • Not the only issue with multi... efficiency loss! 1 [Petter et al. 2016] 3 Key issues: 0 Incompatibility with diamond wire sawing Relative change in V oc (%) -1 due to texturing challenges -2 Poorer wafer quality preventing full benefit -3 of PERC design -4 Severe LID -5 -6 0 200 400 600 800 1000 1200 1400 Light soak time at 70 °C, 0.46 kW/m 2 (hours) K. Petter et al. (Hanwha Q-Cells) presented at 9th International Workshop on Crystalline Silicon for Solar Cell, Tempe Arizona, October 2016
Background & Outline • LID in Cz mono modules due to BO defect – solutions! • LID in multi-PERC ?? • Not the only issue with multi... 3 Key issues: Incompatibility with diamond wire sawing due to texturing challenges Poorer wafer quality preventing full benefit Advanced of PERC design Hydrogenation Severe LID
Background & Outline • LID in Cz mono modules due to BO defect – solutions! • LID in multi-PERC ?? • Not the only issue with multi... • Hydrogenation H+ H- H0
Current Modules Market Share Cell Type: p-type crystalline silicon wafers: mono BSF multi mc-Si HP mc-Si Currently dominated by multi-crystalline BSF cells
Shift to PERC PERC Shift to mono Multi ~75% - - - - - - - - - - - - - < 50% predicted Mono ~25% - - - - - - - - - - - - - > 50%
Our Solutions - Mono
Industry Partners for Advanced Hydrogenation
LID in mono Sequential Photoluminescence Images
Advanced hydrogenation H+ Can’t bond! No Electrons
Advanced hydrogenation H+ H- H0
Commercialisation of Advanced Hydrogenation for Cz • Provide control of the hydrogen charge state • New tools implementing UNSW hydrogenation Asia Neo Tech (Taiwan – LED based tool) o Ke Long Wei (China – Broad spectrum o tool) o Schmid (Germany) DR Laser (China – Laser-based tool) o o Meyer Berger (Switzerland) • New generation of tools in 2018 with solution for multi LID
Evaluation of commercial prototypes
Application to production lines of industry partners PERC cell producers Stable efficiency increase (% absolute ) Manufacturer A +0.8% Manufacturer B +1.0% Manufacturer C +0.7% Manufacturer D +0.9% Manufacturer E +1.5% Manufacturer F +0.8% Manufacturer G +1.8% Manufacturer H +1.2% Manufacturer I +0.7% Average +1.0% 8 second process Final efficiency higher Final efficiency stable B. Hallam et al. 33 rd EUPVSEC (2017).
High voltage commercial PERC cells Using only industrial tools: Plated contacts Laser doped selective Industrial grade emitter p-type Cz mono PERC rear
High voltage commercial PERC cells Using only industrial tools: Plated contacts Average performance with hydrogenation 40.3 mA/cm 2 Jsc Voc 696 mV Laser doped selective FF 72.4 % Industrial grade emitter 20.3 % Eff p-type Cz mono *20 cell batch PERC rear Highest recorded!
SHJ Fabrication at Arizona State University SHJ Cell Ag rear contact ITO (80 nm) n + a-Si:H (10 nm) p- type Cz i a-Si:H (5 nm) p + a-Si:H (10 nm) ITO (200 nm) Ag rear contact
SHJ Fabrication at Arizona State University SHJ Cell Ag rear contact With Advanced ITO (80 nm) Hydrogenation n + a-Si:H (10 nm) 39.5 mA/cm 2 Jsc p- type Cz i a-Si:H (5 nm) Voc p + a-Si:H (10 nm) 707 mV ITO (200 nm) FF 72.1 % Ag rear contact 20.2 % Eff
SHJ Fabrication at Arizona State University SHJ Cell Ag rear contact ITO (80 nm) n + a-Si:H (10 nm) p- type Cz i a-Si:H (5 nm) p + a-Si:H (10 nm) ITO (200 nm) Ag rear contact Cell area: 5.63 cm 2 35.5 mA/cm 2 Jsc Voc 702.7 mV FF 73.8 % Eff 18.4 %
Multi: New Problems Require New Solutions
Charge of Hydrogen and Defects P-type Si High mobility/reactivity n-type Si H + H 0 H - H+ H- H0 P + B - + Fe i D + D 0 D - Ga - + Cr i BO + Dangling bond mc-Si much more complicated: • defects of all charges • varying concentrations • different LID (longer timescales)
Charge of Hydrogen and Defects P-type Si High mobility/reactivity n-type Si H + H 0 H - H+ H- H0 P + B - + Fe i D + D 0 D - Ga - + Cr i BO + Dangling bond H0 passivates grain boundaries
Crystallographic defects need H charge-state control • H+ for trapping Conventional multi • H0 for dispersion • H- for bonding • Multi-step process for multi! Reject cast material UMG multi wafers
Preliminary results on multi p-type SHJ Solar Cells SHJ Cell Ag rear contact ITO (80 nm) n + a-Si:H (10 nm) p- type multi i a-Si:H (5 nm) p + a-Si:H (10 nm) ITO (200 nm) Ag rear contact
Preliminary results on multi p-type SHJ Solar Cells SHJ Cell Ag rear contact ITO (80 nm) n + a-Si:H (10 nm) p- type multi i a-Si:H (5 nm) p + a-Si:H (10 nm) ITO (200 nm) Ag rear contact Record V OC of 695 mV for p-type multi-crystalline silicon (pending independent confirmation)
Preliminary results on multi p-type SHJ Solar Cells SHJ Cell Ag rear contact ITO (80 nm) n + a-Si:H (10 nm) p- type multi i a-Si:H (5 nm) p + a-Si:H (10 nm) ITO (200 nm) Ag rear contact Record V OC of 695 mV for p-type multi-crystalline silicon (pending independent confirmation) • 20 mV higher than record multi PERC cell
Preliminary results on multi p-type SHJ Solar Cells SHJ Cell Ag rear contact ITO (80 nm) n + a-Si:H (10 nm) p- type multi i a-Si:H (5 nm) p + a-Si:H (10 nm) ITO (200 nm) Ag rear contact Record V OC of 695 mV for p-type multi-crystalline silicon (pending independent confirmation) • 20 mV higher than record multi PERC cell • >700 mV will be achieved soon!
LID in multi PERC cells Don’t fire cells 1. • Bad idea (no H passivation of structural defects, poor lifetime, contact formation?) 2. Reduce co-firing temperature 3. Add extra thermal process after co-firing at T< T co-fire • Could be incorporated as a hold at T step during co-firing • Can cause FF problems (fine process window) Left: Relative voltage Right: PL images C. Chan et. al, “Rapid stabilization of HP mc - Si PERC cells” JPV 2016
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