From R&D to Large-Area Modules at Oerlikon Solar
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1245-A01-02
From R&D to Large-Area Modules at Oerlikon Solar
J. Meier, S. Benagli, J. Bailat, D. Borello, J. Steinhauser, J. Hötzel, L. Castens, J-B. Orhan, Y. Djeridane, E. Vallat-Sauvain, U. Kroll, Oerlikon Solar-Lab SA, Puits-Godet 12a, CH-2000 Neuchâtel, Switzerland
ABSTRACT Amorphous silicon single-junction p-i-n and Micromorph tandem solar cells are deposited in KAI-M reactors on in-house developed LPCVD ZnO front TCO’s. An a-Si:H p-i-n cell with a stabilized efficiency of 10.09 % on 1 cm2 has been independently confirmed by NREL. An alternative ZnO/a-Si:H cell process with an intrinsic absorber of only 180 nm has reached 10.06 % NREL confirmed stabilized efficiencies as well. Up-scaling of such thin cells to 10x10 cm2 mini-modules has led to an aperture module efficiency of stabilized 9.20 ± 0.19 % as well independently confirmed by ESTI of JRC Ispra. Micromorph tandem cells with stabilized efficiencies of 11.0 % have been achieved on asgrown LPCVD ZnO front TCO at bottom cell thickness of just 1.3 µm in combination with the in-house developed AR concept. Applying an advanced LPCVD ZnO front TCO stabilized tandem cells of 10.6 % have been realized at a bottom cell thickness of only 0.8 µm. Implementing in-situ intermediate reflectors in Micromorph tandems on LPCVD ZnO reached in a stabilized cell efficiency of 11.3 % with a bottom cell thickness of 1.6 µm.
INTRODUCTION On the path towards achieving grid parity, thin film silicon solar modules offer a significant potential for manufacturing cost reduction. The challenge of amorphous and microcrystalline silicon based technology is the improvement of module performance towards crystalline silicon technology. While at Oerlikon Solar’s customers sites several manufacturing lines based on amorphous and microcrystalline silicon have now been installed, the need for higher efficiencies is the major interest beside cost decrease. Therefore, Oerlikon Solar is concentrating with its R&D group to challenge improved device efficiencies. In this paper we report on the status of amorphous p-i-n single-junction and Micromorph tandems cells using industrial PECVD KAI equipment and in-house developed LPCVD (Low Pressure Chemical Vapor Deposition) ZnO as TCO technology. As light-trapping is one of the most important keys to improve performance, special care on the development of LPCVD ZnO tailored to amorphous or Micromorph tandems has been taken. In addition Oerlikon has developed an in-house AR concept that allows further reducing losses of light coupling into the absorber.
EXPERIMENT The heart of Oerlikon Solar’s thin film PV technology is the KAI PECVD reactor (Plasma Enhanced Chemical Vapor Deposition). To improve deposition rates for solar device-quality amorphous, and especially microcrystalline silicon [1-3], the flat panel display-type reactors were adapted to run at a higher excitation frequency of 40.68 MHz. In this study results were obtained in KAI-M (520x410 mm2) reactors. More details regarding PECVD processes are given in [4-7]. In order to improve light-
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