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Industrial production of multicrystalline silicon solar cells with efficiencies above 18%

ABSTRACT: In this paper, we present the InPERC technology implemented into a multicrystalline silicon (mc-Si) solar cell production of a major Chinese cell manufacturer. Stable average efficiencies over 18% were demonstrated. Best average efficiencies of 18.4% were achieved on mc-Si solar cells without selective emitter with a best cell efficiency of 18.8%. To reduce the cost of ownership (CoO) of the InPERC upgrade, the annealing step after ALD of Al2O3 was successfully skipped by integrating it into the direct tube PECVD without increase of PECVD process time. Furthermore, the Al2O3 thickness was reduced to 4 nm and the etch removal for rear side smoothening to 2 µm without loss in efficiency.

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Industrial production of multicrystalline silicon solar cells with efficiencies above 18%

Silicon surface passivation Al2O3 films grown by atomic layer deposition using low-cost precursors

Naomi Nandakumar, Fen Lin, Bas Dielissen, Floor Souren, Xavier Gay, Roger Gortzen, Shubham Duttagupta, Armin G. Aberle and Bram Hoex.

ABSTRACT: A key concern for the integration of Al2O3 films deposited by atomic layer deposition (ALD) in the photovoltaic industry is its high cost of precursors. This cost can be reduced by replacing conventional semiconductorgrade trimethylaluminium (TMA) with cheaper solar-grade TMA. In this study, Al2O3 films were grown on SoLayTec's InPassion LAB spatial ALD reactor and the level of surface passivation was investigated on both n-type and p-type Czochralski-grown silicon wafers. High effective lifetimes were obtained for Al2O3 films deposited by both grades of TMA, with little difference between the two. Further investigations revealed a lower interface defect density for solargrade TMA and only very small differences in the fixed charge density between the two grades of TMA. These results show that low-cost solar-grade TMA can be utilised for the passivation of n-type and p-type c-Si surfaces.

Keywords: passivation, high-deposition rate, crystalline, silicon, spatial ALD, trimethylaluminium

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Silicon surface passivation Al2O3 films grown by atomic layer deposition using low-cost precursors

Post-deposition thermal treatment of ALD Al2O3 for the passivation of P-type PERC solar cells

Xavier Gay, Floor Souren, Bas Dielissen, Martin Bijker, Roger Gortzen, Damian Pysch, Katrin Weise, Bernd Sander, Ronald Sastrawan.

ABSTRACT: Passivated Emitter and Rear Cell (PERC) solar cell concept is one of the most promising technology for increasing crystalline silicon solar cell efficiency as well as a technology at relatively low production costs compared to other advanced solar cell concepts. Among the different candidates of materials for the passivation of the rear side, aluminum oxide (Al2O3) deposited by spatial atomic layer deposition (ALD) is very attractive due to its excellent passivation properties and its high processing throughput. In this work, we investigate the influence of the post-deposition thermal treatment of spatial ALD Al2O3 on the passivation properties of the Al2O3/SiNx stack system. It is shown that for an ALD Al2O3 layer thickness of 10 nm, a sufficient high annealing temperature is necessary to prevent blistering and to achieve excellent passivation, which has been investigated for two SiNx deposition methods: remote and direct plasma enhanced chemical vapor deposition (PECVD). Furthermore, it has been investigated that in the case of using thinner ALD Al2O3 layers down to 6 nm as well as by adapting the SiNx recipe of the direct plasma, the post-deposition anneal can be avoided, which is beneficial for further down scaling of the production costs of the PERC solar cell.

Keywords: c-Si, Silicon, Passivation, Annealing

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Post-deposition thermal treatment of ALD Al2O3 for the passivation of P-type PERC solar cells

Firing-stable and blister-free spatial ALD Al2O3/SiNx stack for industrial PERC solar cells

F.M.M. Souren, B. Dielissen, X. Gay, R. Gortzen, X.L. Jiang, W.Z. Ban, W. Shan, R. Hoyer, X. Mao, X. Qu.

ABSTRACT: We have studied the passivation effect of ALD Al2O3/SiNx stacks as a function of H2O concentration during atomic layer deposition (ALD), with and without post-deposition annealing. Firing-stable and blister-free ALD Al2O3/SiNx stacks with implied Voc values larger than 700 mV can be relatively easy achieved if post-ALD annealing is employed. While blistering has been observed in the ALD Al2O3/SiNx stacks without post-deposition annealing. The number of blisters is found to be proportional to the H2O concentration in the ALD recipe used for Al2O3 deposition. By controlling H2O concentration at a reasonable level in the mixture of precursors, good passivation of Al2O3 to Si surface can be obtained with implied Voc up to 680 mV with no post-deposition annealing being applied.

Keywords: c-Si, Silicon, Passivation, Annealing

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Firing-stable and blister-free spatial ALD Al2O3/SiNx stack for industrial PERC solar cells

Integration of spatial ALD Aluminium Oxide for rear side passivation of p-TypePERC/PERL solar cells

E. Cornagliotti, L. Tous, A. Uruena, A. Rothschild, R. Russell, V. Lu, S. Radosavjlevic, J. John, J. Toman, M. Aleman, F. Duerinckx, J. Poortmans, J. Szlufcik, B. Dielissen, F. Souren, X. Gay, R. Görtzen, B. Hallam.

ABSTRACT: In this paper we present an overview of the integration of amorphous aluminum oxide (Al2O3) as rear side passivation layer for large area industrial PERC solar cells (i-PERC). The technique used for the deposition of the Al2O3 layers is spatial Atomic Layer Deposition (ALD), for its industrial relevance due to the high deposition speed and low Trimethyl-Aluminum (TMA) consumption. After analyzing the surface passivation properties, we will describe how Al2O3 can be integrated in an i-PERC process flow in a simple and cost-effective way, while maintaining high levels of solar cell efficiency. In particular, a special effort is devoted in finding solutions for process simplification and in the reduction of the cost per wafer (€/W) of the spatial ALD process step. Top efficiencies of 20.1 % and 20.6 % have been reached (Cz-Si, 6 inch cells) when coupling a spatial ALD Al2O3 rear passivation to a standard i-PERC integration flow with front Ag-screen printed or Ni/Cu/Ag plated contacts, respectively. Besides passivation, ALD Al2O3 can also be used as doping source of aluminum to form localized p+ back surface field (BSF) regions at the rear contact by means of laser processing. In this way, dielectric opening and BSF are formed simultaneously and firing step is not needed anymore, leading both to a suppression of Al2O3 blistering and optical enhancement. This process is a suitable complement of front contact formation based on plating schemes. Ni/Cu/Ag-plated solar cells with rear laser doping from ALD Al2O3 layers have been fabricated with efficiencies topping 20.4 % (FF = 79.7 %) and outperforming the control group featuring local BSF formed via a firing step.

Keywords: Aluminum oxide, PERC, passivation, ALD, spatial ALD, laser doping.

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Integration of spatial ALD Aluminium Oxide for rear side passivation of p-TypePERC/PERL solar cells

Implementation of a multicrystalline ALD-Al2O3 PERC-technology into an industrial pilot production

R. Sastrawan, D. Pysch, M. Bijker, F. Delahaye, B. Dielissen, W. Eipert, X. Gay, R. Görtzen, A. Hoffmann, B. Latzel, M. Lenes, X. Mao, S. Patzig+Klein, X.Qu, B. Sander, C. Schmitt, F. M. M. Souren, A. Träger, K. Weise, S. Yang and H. Nussbaumer

In this paper, we present results of the implementation of the InPERC technology into an industrial pilot production of a major Chinese cell manufacturer. The process sequence utilizes all production equipment of the standard production line for screen printed full area Al-BSF solar cells. In addition, the rear surface is smoothened. For this purpose, the hardware of one existing standard InOxSide for wet chemical edge isolation is upgraded to InOxSide+ without changing the footprint of the tool. The rear side is passivated using SoLayTec's InPassion ALD mass production machine for ultrafast spatial atomic layer deposition (ALD) of Al2O3. The SiNx capping layer is deposited using standard PECVD equipment of the existing production line. Furthermore, a laser is used to open the rear side contacts prior to screen printing the metallization. In a first step, the InPERC ALD technology was developed on CZ-Si 156 x 156 mm² wafers at RENA. Average cell efficiencies of 19.5% were achieved with screen+printed metallization and without selective emitters: an increase of about 1% abs compared to our full Al-BSF baseline of about 18.5%. It was found that a surface smoothening by removal of about 4 μm is sufficient to reach implied Voc values of over 700 mV and 680 mV for CZ-Si and mc-Si material, respectively. This leads to an efficiency gain of up to 0.5% abs due to surface smoothening. The passivation quality of the layer stack is significantly improved by an annealing step after the ALD process. It was successfully shown that by using an optimized recipe for the PECVD process of the capping layer this post deposition anneal (PDA) can be skipped. Thus, the full potential of the excellent passivation quality of ALD Al2O3 can be obtained at lowest cost of ownership. It was found, that – by use of a suited laser and aluminum paste – damage to the silicon by the laser ablation can be healed effectively by a deep formation of the local Al-BSF. The full potential of the InPERC technology was demonstrated at RENA with direct Ni/Ag plating as front side metallization and FireFOXTM as front passivation. A best efficiency of 20.3% was achieved. The InPERC ALD technology on CZ-Si was transferred to a mc+Si industrial pilot production of a major Chinese cell manufacturer. It was found that an Al2O3 layer thickness of 7 nm and even 4 nm could be applied without loss in efficiency, further reducing cost of ownership. On mc-Si material efficiency gains of about 0.6%abs were demonstrated. Top average efficiencies of 18.0% could already be achieved up to now without a selective emitter.

Keywords: ALD, Al2O3, PERC, i-PERC, Al-LBSF, Aluminum Oxide, Atomic Layer Deposition, Surface Passivation.

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Implementation of a multicrystalline ALD-Al2O3 PERC-technology into an industrial pilot production

Excellent Surface Passivation of Silicon at Low Cost: ALD Aluminium Oxide from Solar Grade TMA

Atomic layer deposited (ALD) AI203 films are not yet applied in the PV industry despite their excellent performance in the lab. A major challenge is the usage of expensive semiconductor (semicon) grade trimethylaluminium (TMA) as the AI precursor. The cost of ownership for ALD AI203 passivation can be significantly reduced if lower purity solar grade TMA is used. Earlier work bij Dingemans et al.[1] found no significant difference for ALD AI203 fabricated by semincon & solar grade TMA. But is was conducted on al lab-scale tool with fairly small sampling size, and more detaild are yet to be explored.

Fen Lin, Naomi Nandakumar, and Bram Hoex from SERIS, National University of Singapore. Bas Dielissen, Roger Görtzen, from SoLayTec.

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Excellent Surface Passivation of Silicon at Low Cost: ALD Aluminium Oxide from Solar Grade TMA

The quaranteed cell efficiency increase, could be a fairy tale

市场的形势依然不如期望,所以我们都必须努力使已经是谷底价格的太阳能光伏更具吸引力!设备供应商可透过引进能进一步提高效率并且合算的新设备来达到这个目的,同时我们也有义务让客户知道他们所得到的不会是一个童话故事。我不得不承认,一些设备供应商只告诉他们的客户不全的事实,然而他们为什么要这样做?我所能想到唯一的原因是他们想再次出售新机器 .

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The quaranteed cell efficiency increase, could be a fairy tale

In anderhalf jaar van lab naar fab

Door Alexander Pil (Mechatronica & machinebouw)

Slechts achttien maanden gaf SolayTec zichzelf om zijn bestaande R&D -tool voor atoomlaagdepositie om te toveren tot een systeem dat in de smaak zou vallen bij veeleisende zonnecelfabrikanten. De TNO-spin-off slaagde daarin door deelontwikkelingen parallel te laten verlopen en de kritieke onderdelen fysiek na te bouwen en uitvoerig te testen. Dat gaf zo veel vertrouwen dat de gebruikelijke protostap durfde over te slaan. Afgelopen kwartaal verkocht SoLayTec zijn eerste productiemachine voor atoomlaagdepositie (ALD).

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In anderhalf jaar van lab naar fab

In pursuit of the super PERC cell

Aude Rothschild, Richard Russell, Joachim John, Philip Pieters and Jef Poortmans/imec

PERC cells: Imec reports on recent innovations in some of the key steps for fabricating PERC-type solar cells: a new metallization scheme, a promising ALD - AL2O3 -based passivation layer and the integration of very thin cells into a module. In all these improvements, imec goes beyond current Si PV boundaries by using industrial manufacturable processes.

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In pursuit of the super PERC cell
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