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                Titel:
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                High power n-type Metal-Wrap-Through cells and modules using industrial processes
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                Auteur(s):
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	Guillevin, N.;  Heurtault, Benoit;  Geerligs, L.J.;  Aken, B.B. van;  Bennett, I.J.;  Jansen, M.J.;  Weeber, A.W.;  Bultman, J.H.;  Jianming, Wang;  Ziqian, Wang;  Zhai, jinye;  Zhiliang, Wan;  Shuquan, Tian;  Wenchao, Zhao;  Zhiyan, Hu ;  Gaofei, Li ;  Jingfeng, Xiong 
 
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                Gepubliceerd door:
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                Publicatie datum:
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                ECN
                Zonne-energie
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                30-9-2013
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                ECN publicatienummer:
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                Publicatie type:
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                ECN-M--13-028
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                Conferentiebijdrage
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                7
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        Samenvatting:
        This paper reviews our recent progress in the development of metal wrap through (MWT) cells and modules, produced from n-type Czochralski silicon wafers. The use of n-type silicon as base material allows for high efficiencies: for front emitter-contacted industrial cells, efficiencies above 20% have been reported. N-type MWT (n-MWT) cells produced by industrial process technologies allow even higher efficiency due to reduced front metal coverage. Based on the same industrial technology, the efficiency of the bifacial n-MWT cells exceeds the efficiency of the n-type front-and-rear contact and bifacial “Pasha” technology (n-Pasha) by 0.1-0.2% absolute, with a maximum n-MWT efficiency of 20.1% so far.
Additionally, full back-contacting of the MWT cells in a module results in reduced cell to module (CTM) fill factor losses. In a direct 60-cell module performance comparison, the n-MWT module, based on integrated backfoil, produced 3% higher power output than the comparable tabbed front emitter-contacted n-Pasha module. Thanks to reduced resistive losses in copper circuitry on the backfoil compared to traditional tabs, the CTM FF loss of the MWT module was reduced by about 2.2%abs. compared to the tabbed front emitter contact module. A full-size module made using MWT cells of 19.6% average efficiency resulted in a power output close to 280W. 
Latest results of the development of the n-MWT technology at cell and module level are discussed in this paper, including a recent direct comparison run between n-MWT and n-Pasha cells and results of n-MWT cells from 140µm thin mono-crystalline wafers, with only very slight loss (1% of Isc) for the thin cells. Also reverse characteristics and effects of reverse bias for extended time at cell and module level are reported, where we find a higher tolerance of MWT modules than tabbed front contact modules for hotspots.
    
    
        
        
    
    
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