Preu R large-area P-type HIP-MWT silicon solar cells with screen printed contacts exceeding 20% efficiency

physica status solidi (RRL) - Rapid Research Letters (Impact Factor: 2.14). 08/2011; 5:286-8. DOI: 10.1002/pssr.201105311


We present metal wrap through (MWT) silicon solar cells with passivated surfaces based on a simplified device structure. This so-called HIP-MWT structure (high-performance metal wrap through) does not exhibit an emitter on the rear side and therefore simplifies processing. The confirmed peak efficiency of the fabricated solar cells with an edge length of 125 mm, screen printed contacts and solder pads is 20.2%. To our knowledge, this is the highest value reported for large-area p-type silicon solar cells to date.
Schematic structure of the fabricated HIP-MWT solar cells
(© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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Available from: Daniel Biro
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    • "Compared to conventional H-pattern solar cells with surface passivation, HIP-MWT devices require only one additional process step and are therefore well suited for cost-optimised production of MWT-PERC solar cells. Solar cells with a conversion efficiency exceeding 20 % based on the HIP-MWT structure were presented last year [5]. Although already aiming at an industrially applicable process sequence, the cells have been made from rather costly float-zone silicon (FZ-Si) with an edge length of 125 mm. "
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    ABSTRACT: This work presents large-area metal wrap through (MWT) solar cells with passivated surfaces made from Czochralski grown silicon (Cz-Si). Besides further improvement in conversion efficiency, the paper addresses industrial applicability of the fabrication process and technology. Three different base materials are compared – conventional boron-doped Cz-Si, gallium-doped Cz-Si and boron-doped magnetically cast Cz-Si (mCz-Si). Stencil printing is applied for front contact formation resulting in increased aspect ratio and finger homogeneity and thus low series resistance losses. Regarding material consumption, the presented cells allow for a reduction of silver usage by 30%. The peak efficiency for cells made from mCz-Si with an edge length of 156 mm is 20.2% (confirmed) in the annealed state.
    Full-text · Article · Jan 2012 · Green
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    • "We further improved the MWT-PERC structure by implementing laser-doped selective emitter structures as well as emitter passivation by a thin thermally grown silicon oxide layer [6]. This improved front side structure showed conversion efficiencies of up to 20.2% for large-area floatzone (FZ) silicon solar cells on a related cell architecture called HIP-MWT [7]. "
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    ABSTRACT: We present metal wrap through passivated emitter and rear solar cells (MWT-PERC) on monocrystalline p-type silicon featuring laser-doped selective emitter structures in combination with either screen-printed (SP) or more advanced dispensed front side contacts. Thermally grown silicon oxide layers serve as emitter and rear surface passivation. Laser-fired contacts connect the SP aluminum rear contact to the silicon base. The rear side features solder contacts for both polarities. Conversion efficiency values of 20.6% for float-zone and 20.1% for Czochralski-grown silicon (not stabilized) are achieved on large-area cells with 149 wafer size. These are within the highest values reported for large-area p-type silicon solar cells to date. Analytical modeling enables a consistent description of the devices and allows for determining the dominating loss mechanisms.
    Full-text · Article · Jan 2012 · IEEE Electron Device Letters
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    ABSTRACT: To overcome limitations in efficiency originating from the front side of a crystalline silicon solar cell, the concept of the selective emitter has been investigated in recent years. Several approaches have been presented and tested for their industrial feasibility. Although almost all concepts are able to achieve a gain in conversion efficiency, not all technologies are realizable due to process complexity and possible major modifications necessary for retrofitting existing production lines. This motivates a simple process flow for the fabrication of a selective emitter structure. Laser Doping from phosphorous silicate glass (PSG) is a cost attractive approach, as only one additional processing step is required for selective emitter formation and no consumables are used. In this work solar cells on both mono-and multicrystalline silicon with selective emitter have been fabricated. A beam splitter in conjunction with a high power laser system has been used to allow for high throughput processing with 10 parallel laser beams. Solar cell parameters are shown and discussed. To investigate possible hot spots under reverse bias conditions of the shallow emitter, Dark Lock-In Thermography (DLIT) measurements have been conducted and reveal no hot-spots.
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