Print Email Facebook Twitter The latest developments in bifacial solar cells at ECN part of TNO Title The latest developments in bifacial solar cells at ECN part of TNO Author Stodolny, M.K. Janssen, G.J.M. Anker, J. Tool, C.J.J. Mede, A.A. Manshanden, P. van Aken, B.B. Geerlings, L.J. Publication year 2018 Abstract The performance of current industrial solar cells is for a large part limited by recombination at metallic contacts. A solution to overcome this is to screen minority carriers from the metal by using so-called passivating carrier-selective contacts. Using carrier-selective contacts based on doped polysilicon layers combined with tunnel oxides, efficiencies well above 25% have already been reached on front and back contacted cells on laboratory scale. In this paper we will present our latest developments in bifacial cells featuring polysilicon carrier-selective passivating contacts which can be seen as an upgrade to bifacial cell architectures such as PERC+ and PERT. First, we will present the upscaling and application of these polysilicon passivating contacts to 6” bifacial cells featuring both n+ and p+polysilicon contacts (n+ and p+poly-Si), using industrial screen printed and fired metallization. The main challenges for such solar cells are keeping the contact recombination low, while applying a cost effective, industrial metallization approach. The contact mechanism of commercial silver and silver/aluminum pastes on both n+ andp+poly-Si layers has been extensively studied using scanning and tunneling electron microscopy (SEM, TEM) and Jo,contact and contact resistance characterization, using transmission line measurements (TLM). These experiments lead to a consistent description and understanding of the polysilicon passivating contacts and its interaction with the fire through metallisation. The contact recombination on n+poly-Si surfaces has been reduced down to 80 fA/cm2 while the contact resistance is kept low enough to enable FF > 79.5%. Voc as high as 683 mV has been obtained enabling initial cell efficiencies of 21.5%. Further optimization of the processing and non-contacted passivation of the polysilicon layer stack has yielded record low values for Jo on textured surfaces: we present Jo and implied Voc measurements with best values of <1 fA/cm2 and 741 mV for n+poly-Si, and ~8 fA/cm2 and 724 mV for p+poly-Si on textured n-Cz wafers, which are maintained after firing by improvement of the hydrogenation scheme. In this study we also present our improvements of p+poly-Si passivation on industrially relevant textured surfaces by means of advanced hydrogenation schemes, involving novel dielectric stacked layers, and modification of the B-profile leading to a record passivation level of ~8 fA/cm2 and 724 mV before firing and ~9 fA/cm2 and 722 mV after firing. The results promote industrial implementation of p+poly-Si on 6’’ bifacial cells with excellent passivation properties and compatibility with screen-printed and fire-through metallization, especially as our latest results show Jo,contact being reduced down to 200 fA/cm2. Bifacial solar cells, have been manufactured with industry compatible processing with front-and-rear passivating contacts with efficiencies above 20% in the first attempt and this developments shows a potential of 23% with a bifaciality factor of 90%. Subject Energy EfficiencyEnergyEnergy / Geological Survey Netherlands To reference this document use: http://resolver.tudelft.nl/uuid:b6ab9f44-9224-47c7-a7a4-0278be2b2846 TNO identifier 843284 Source 28th Workshop on Crystalline Silicon Solar Cells & Modules: Materials and Processes, Winter Park, Co, USA, 12-15 August 2018, 1-8 Document type conference paper Files To receive the publication files, please send an e-mail request to TNO Library.