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Lean Integration of p- and n-type polySi Passivating Contacts Activated via Short or Long Annealing
J.J. Diaz Leon, C. Allebé, A. Ingenito, G. Nogay, A. Descoeudres, G. Christmann, F.-J. Haug, M. Despeisse, C. Ballif, S. Nicolay
Silicon Materials and Cells
Subtopic: High Temperature Route for Si Cells
Event: 37th European Photovoltaic Solar Energy Conference and Exhibition
Session: 2DV.3.12
ISBN: 3-936338-73-6
0,00 EUR
Document(s): poster


Passivating contacts based on a thin silicon oxide/doped polysilicon stack activated during a high temperature process (high-temperature passivating contacts or HTPCs) are increasingly adopted in industry. Compared to traditional homojunction technologies such as passivated emitter rear cell (PERC) or aluminum back surface field (Al-BSF) solar cells, HTPCs offer a high degree of surface passivation and charge extraction over the full cell area [1]. Compared to amorphous silicon-based heterojunction (HJT), HTPCs can be combined with broadly used high temperature processes such as firing through of metal paste, phosphorous and boron diffusion or thermal oxide growth. Different deposition conditions have been developed for the deposition of polySi, including PECVD, LPCVD and PVD. Doping can be done in-situ or ex-situ, depending on the deposition technique. Regarding the contact activation of the HTPC stack, it can either be done either during a “short annealing” step (similar to a firing step) or during a “long annealing” step in a tube furnace [1,2]. This work will first show the general principles of short and long annealing contacts. Then, insitu doped p- and n-type SiCx-based HTPCs deposited by PECVD and activated during either short or long annealing will be presented, showing the relationship between material/interface properties (doping, thickness, crystallinity) and their passivation and contacting parameters. High-level of passivation with iVoc > 730 mV will be presented for both polarities. At the same time, contacting with firing-through metallization with thickness < 100 nm, minimal passivation damage and contact resistivity < 5 mOhm.cm2 will be discussed. Finally, the integration of these devices at the back of PERC and PERT devices using hydrogenation by dielectrics combined with firing-through metallization will be presented, showcasing efficiencies > 22.5 % (22%) for n-(p-)type contacts, respectively. Passivation and extraction losses will be analysed and related to device efficiency. Integration routes, possible limitations and alternatives to fabricate Si solar cells presenting bothpolarity HTPCs and efficiency > 25% using a lean process will be analysed and discussed.