Oliver Doll

La presente invention concerne une composition de gravure pour la gravure de surfaces constituees de SiO 2 , de SiN x ou d'oxydes conducteurs transparents (TCO), comprenant au moins une phase aqueuse et au moins un agent permettant d'augmenter les vitesses de gravure, et l'utilisation de ladite composition dans des procedes de production dans l'industrie electronique.

MWT (metal wrap through) solar cells [1] address the target of reaching higher efficiencies, while only requiring two additional process steps compared with conventional solar cells [2]. To further reduce the production costs of MWT solar cells one possibility is to reduce the breakage, which mainly occurs during the production from cell to module and is caused by laser grooves on the rear. These laser grooves isolate the n- from the p-contacts and almost run across the whole cell. For this purpose two alternative isolation methods have been developed; one is based on the etching paste SolarEtch® SiD [3], which etches a groove that replaces the laser groove; the other developed method is based on the diffusion barrier SolarResist™ [4]. Apart from the advantage of less breakage the damaging impact of the laser on the crystalline structure of the wafer is avoided. The functionality of the developed methods has been verified on appropriate test structures. Furthermore the adaptability of the methods has been proved by processing functional MWT solar cells with pFF values of around 82%. At the same time the comparability with the laser groove has been shown by producing reference cells. The reliability was shown during repeated runs of MWT cell production.

La presente invention concerne un procede de fabrication de cellules solaires structurees a haute efficacite et d'elements photovoltaiques comportant des regions de dopage different. La presente invention concerne egalement des cellules solaires a efficacite accrue fabriquees selon ledit procede.

Gegenstand der vorliegenden Erfindung ist ein Verfahren zur Herstellung von Solarzellen mit selektivem Emitter unter Verwendung einer verbesserten Atzpastenzusammensetzung, welche eine wesentlich verbesserte Selektivitat gegenuber Siliziumschichten aufweist. In einer bevorzugten Ausfuhrungsform (Abbildung. 4) umfasst das erfindungsgemasse Verfahren zur Herstellung von Solarzellen mit einstufigem Emitter die Verfahrensschritte: I. Texturierung der Oberflache II. Phosphordotierung (ca. 40Q/sq Diffusion von P0CI3) III. Lokales Atzen der PSG- und Silizium- Schicht, wodurch eine Leitfahigkeit Im bereich von -90 - 100 [Omega] /sq erzielt wird (PSG = Phosphor- SilicatGlas) und Reinigung des Wafers. IV. PSG Atzung V. Maskierung mit Antireflexionsschicht (ARC Deposition) mitteis "plasma enhanced chemical vapor deposition" (PECVD) von Siliziumnitrid (SiNx) VI. Siebdruck zur Metallisierung der Oberflache (Frontseite) und der Ruckseite mit anschliessendem Sintern (Cofiring). VII. Kant...

Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung von strukturierten, hocheffizienten Solarzellen sowie vom Photovoltaikelementen, die Regionen unterschiedlicher Dotierung aufweisen. Gegenstand der Erfindung sind ebenfalls die so hergestellten Solarzellen mit gesteigerter Effizienz.

A simple selective emitter process for silicon solar cells is presented in this work. The highly doped POCl3 diffused emitter of a multicrystalline solar cell is structured by screen printing of an etching paste, developed by Merck KGaA. The emitter is etched back to a sheet resistivity of around 100 Ω/sq in the main part of the cell area. The emitter regions below the later metallization fingers remain n++ doped. For this technical approach only one diffusion step is necessary. After optimisation of the screen layout a fill factor of 79.5% has been achieved while the short circuit current remains high. Up to now a gain in Voc of 4 to 5 mV and a gain in Jsc of 0.5 mA/cm2 is possible on multicrystalline wafers in comparison to cells with a homogeneous 65 Ω/sq emitter. The cell efficiency is therefore about 0.45% absolute higher.

Die vorliegende Erfindung betrifft eine neue druckbare Paste in Form eines Hybridgels auf Basis von Precursoren anorganischer Oxide, welche in einem vereinfachten Verfahren zur Herstellung von Solarzellen verwendet werden konnen, wobei das erfindungsgemase Hybridgel sowohl als Dotiermedium als auch als Diffusionsbarriere fungiert.

Couches de passivation a base d'oxyde d'aluminium qui ont en meme temps une action en tant que barriere de diffusion pour l'aluminium et d'autres metaux par rapport aux couches de tranche sous-jacentes. La presente invention concerne en outre un procede et des compositions adaptees permettant de fabriquer ces couches.

Cette invention concerne un procede pour le depot sans contact de nouvelles compositions de gravure sur des surfaces de dispositifs a semi-conducteurs et la gravure ulterieure de couches fonctionnelles situees a la surface desdits dispositifs a semi-conducteurs. Lesdites couches fonctionnelles peuvent servir de couches de passivation superficielles et/ou de revetements anti-reflets (ARC).

Key parameters in the manufacturing of the rear metallization for PERC solar cells are the thermal budget within the firing process, the materials used, e.g. metallization paste, and the geometry of the rear-side openings. As a further key parameter, the way of opening the dielectric passivation layers is investigated. Three different methods for locally removing a dielectric layer were analyzed, including one approach by laser processing (using laser irradiation in a short and ultrashort pulse length regime) and an other one by screen printing an etching paste. After locally removing the passivation stack, the rear-side metallization was carried out by application of different Al pastes and firing profiles. From SEM pictures and comparisons of the width of the local openings after structuring and after firing, different general statements were deduced as about the influence of the structuring width, the influence of the firing profile or the relation of the method of structuring with the formation of the contact area.

Die vorliegende Erfindung betrifft Zusammensetzungen, welche besonders gut geeignet sind zum Atzen und Strukturieren von transparenten, leitfahigen Antireflektionsbeschichtungen und von entsprechenden Stapelschichten, die vorzugsweise in beruhrungsempfindlichen Bildschirmen oder Anzeigeelementen enthalten sind. Letztere werden allgemein auch als beruhrungssensitive Displays, Touch-Panels oder Touch Screens bezeichnet. Im speziellen handelt es sich um Zusammensetzungen, durch die selektiv feine Strukturen in leitfahige transparente oxidische Schichten und in entsprechende Schichtstapel geatzt werden konnen.

This paper presents an up-scalable solution for the formation of doped areas based on inkjet printing of boron and phosphorous doping inks. The influence of the thickness of the inkjet-printed doping source layers and the diffusion temperature on the sheet resistance is evaluated. In addition, the doping profiles are measured. For a diffusion temperature of 950 °C a sheet resistance of 50 Ω/sq is achieved with the boron ink. At the same temperature a sheet resistance of 18 Ω/sq is achieved with the boron ink. The process is then for the first time applied for the fabrication of back-contact back-junction solar cells with inkjet-printed p-emitter. The best solar cell features an efficiency of η = 20.6 %. To date, these are the best solar cells with an inkjet-printed doping source. Lifetime samples that are processed in parallel exhibit an emitter saturation current density below 90 fA/cm.

Experiments in which TMAH in cleaning mixtures was replaced stepwise with choline have revealed that choline has a stabilizing effect on the resulting mixtures attributable to its role as a sacrificial reductant. The effect of concentration on the half-lifetime of DEHP and on bath stability (delay time) of both APM and NC have also been investigated. The concentration dependence may be partly due to the intrinsic metal contamination of the CA which also affects the rate of degradation.

The use of sol-gel materials can simplify the industrial fabrication of high-efficiency silicon solar cells if a suitable deposition method is established. In this work, we investigate the possibilities to adapt a borosilicate glass sol-gel to provide a stable screen printing process. This material has previously been used as a boron dopant source for silicon solar cells. We now use an adjusted synthesis process, with an increased gelling time and different additives. This changes the rheological properties (i.e., the elastic and viscous moduli G′ and G″) in a way that avoids the dripping of paste through the screen and that stabilizes the material transfer in subsequent printing steps. Using this synthesis process, we were able to show a printing process with long-term stability of more than 500 prints. When comparing the adjusted to the initial paste, we show that, after thermal treatment, the obtained thin films are very similar in terms of their constitution, with a refractive i...

The realization of high-efficiency silicon solar cell designs like rear contacts, local back surface fields or selective emitters in industrial solar cell production, depends on the existence of cost-effective processing techniques. This report introduces the inkjet-ready isishape SolarResistTM diffusion barrier solution. It can be used to directly print diffusion barrier layers for the local formation of highly-doped regions without additional structuring. Thin films of 190 nm thickness work as a barrier against industrially relevant phosphorus diffusions. No adverse effect on the charge carrier lifetime is observed. Printed line widths of 90 μm are achieved, and the minimum gap width between lines is 50 μm.

The development and improvement of silicon solar cells is often based on a top-down approach, achieving highest conversion efficiencies and then translating it to industrial equipment and fabrication routes. This work presents an alternative option to derive research and fabrication strategies focused on cost of ownership calculations. Given the necessary tools and insight into feasible production routes, this attempt can be very helpful and rewarding for (small) research facilities, existing solar cell fabrication plants or interested investors in the solar industry. A research strategy is exemplarily derived for the goal of industrially feasible back-contact back-junction solar cells, but many aspects can be generalized for different purposes. Several different fabrication routes are shown and compared to a PERC fabrication route. We find that a co-diffusion approach can offer significant cost reduction potential on cell level, from +21 %rel down to -2%rel.

Up to now most spin-on diffusion sources based on a wet chemically created boron-silicate glass (BSG) lead to a strongly degraded carrier lifetime after diffusion. In this study a spin-on boron diffusion source is applied to the fabrication of large area n-type CZ bifacial solar cells and the performance of the spin-on source is compared to a BBr3 boron diffusion concerning the resulting lifetime and emitter saturation current J0e, shunting behaviour and external quantum efficiency. Comparable J0e values and a comparable lifetime were achieved resulting in a top efficiency of 19.38% in comparison to a top efficiency of 19.60% achieved by BBr3 diffusion. Further investigation of the electrical parameters showed the possibility of improvement in cell performance.

This study presents a new developed, inline applicable dispensing platform that is equipped with an advanced version of previously introduced parallel dispensing print heads. At process speeds of up to 700 mm·s and a substantially improved process stability, recent cell results on industrial 90 Ω/sq. emitters showed an efficiency increase of up to +0.4%abs. in comparison to standard single screen printing technology. Top values of 19.4% using standard Al-BSF technology were reached in this study. A key improvement of the technology is the new ability to process certain metal pastes originally designed for screen printing applications and thus keep in track with fast emerging paste development. Successfully evaluated screen printing pastes then can be rheologically adapted in order to reach ultrafine contact fingers at high aspect ratios and extract the whole advantage of this non-contacting printing technology.

We present a new selective emitter technology for industrial type passivated emitter and rear cells (PERC). After double sided texturing and POCl3 diffusion (45 Ω/sq), we deposit an etch barrier by inkjet printing. We then polish the textured rear surface by a single sided wet chemical polishing process removing about 8 μm of silicon at the rear. During the rear polishing, the reactive gas phase of the polishing bath etches about 50 nm of the front side emitter in between the etch barrier fingers. We name this novel selective emitter technology gas phase etch back (GEB). The GEB emitter achieves saturation current densities J0e of 67 fA/cm² at a sheet resistance of 88 Ω/sq compared to 110 fA/cm² for a homogeneously POCl3-diffused emitter with 90 Ω/sq. Applying the GEB selective emitter to largearea PERC solar cells with screen-printed metal contacts, we obtain up to 20.3% conversion efficiency, which is one of the highest conversion efficiencies reported so far for industrial type PERC solar cells. The reference PERC cell with homogeneously POCl3-diffused emitter of 70 Ω/sq sheet resistance obtains 20.0% efficiency. The IQE analysis reveals a strongly improved blue response of the GEB selective emitter.

MWT (metal wrap through) solar cells allow higher efficiencies, while only requiring two additional process steps. One of these process steps – the contact isolation between the external n-contact on the rear and the rear p-contact is the focus of this work. The possibility of realizing this isolation by the etching paste isishape SolarEtch SiD instead of a laser groove, which was presented at this conference two years ago, is investigated further. Moreover, this rear contact isolation is combined with the paste driven edge isolation simultaneously which was relocated to the rear of the solar cell. In addition to the experimental approach, the two isolation technologies as well as an isolation implemented by a thermal oxide, which works as a diffusion barrier and passivates the surface at the same time, were simulated to validate the experimental results. A proof of concept is given by two MWT cell runs, which show high parallel resistances and indicated higher efficiencies for the ...

This paper presents a novel approach for the formation of separated doped areas, where the diffusion barrier isishape SolarResistTM is inkjet-printed prior to a plasma-enhanced chemical vapor deposition (PECVD) process of boronand phosphorus-doped silicate glasses (BSG, PSG). This allows for very accurate single-sided definition of doped patterns without the use of masking and etching of diffusion barriers, diffusion sources or diffused areas. The printed patterns themselves are characterized regarding their thickness. The areas with the printed diffusion barrier are characterized with respect to their sheet resistance Rsh and their doping profile. The barrier effect was demonstrated for diffusion plateau times up to 30 min at 1050°C against diffusion from BSG-layers and for the same plateau time at 850°C against diffusion from PSG-layers.

ABSTRACT An advanced and cost effective process for edge isolation of silicon solar cells by strongly local deposition of etching paste isishape SolarEtch® SiD is presented. The deposition of the paste was carried out by deposition technique being free of contact to substrate, namely dispensing. Basic deposition parameters were figured out and later on refined by design of experiment applying elaborated sub-design. In order to evaluate isolation properties of the new process, experimental trials focusing on process step of edge isolation of standard solar cells were conducted by applying different deposition conditions. For this purpose, experimental trials were sub-divided into two phases: firstly, evaluation of new concept and secondly, its validation by applying industrial conditions of mass production. Conventionally isolated wafers, e. g. by laser scribing, were taken as reference. Comparison of paste-isolated batches with reference batches provided clear evidences for improved cell performances after isolation by etching paste over reference batches. The main beneficial factor for improving solar cell’s performances was identified to originate from increased values of JSC. Isolation process by paste was supplemented by ES&H considerations which provided evidence for environmentally friendly process conduction being superior to single side etching.

Die vorliegende Erfindung betrifft ein schnelles und kostengunstiges lokal durchfuhrbares Verfahren zur nasschemischen Randentschichtung von "Solarmodulen", indem fur diesen Zweck geeignete Atzpasten aufgetragen und nach erfolgter Reaktion die Pastenreste entfernt werden bzw. die Substratoberflache in geeigneter Weise gereinigt wird. In dem Verfahren wird eine fur den Zweck neu entwickelte Atzpaste eingesetzt.

Processing of advanced solar cell designs like PERL or back junction solar cells can only be realized by applying local diffusion designs. The inkjet-printable diffusion barrier solution isishape SolarResist™ is a straight forward alternative to full area dielectric layers in combination with structuring techniques as an indirect method to form local diffusion barriers. Barrier function against both boron and phosphorus diffusion is shown even for low resistivity diffusion profiles. No degradation in carrier lifetime after annealing of the inkjet-printable diffusion barrier solution can be determined. A diffusion barrier line width and gap minimum of approximately 50μm can be achieved by inkjet printing.

This study presents the application of HPLC with UV-VIS detection for the direct determination of the concentration of complexing agents in silicon surface cleaning baths. Direct concentration determination is necessary for evaluating the stability of a CA for application in APM+ . The pyridinone-type complexing agents studied appear to react differently in APM+ and hydrogen peroxide The monitoring technique presented could be applied to other complexing agents as well.

Borosilicate glass films deposited by chemical vapor deposition are used as boron dopant sources in silicon solar‐cell manufacturing, to reduce the fabrication costs of, e.g., back‐contact back‐junction (BCBJ) solar cells. Herein, an alternative dopant source is investigated, which can replace such layers by a printing step. The necessary paste is synthesized by the sol–gel method and optimized for screen printing as demonstrated. The liquid paste can be converted to a glass by thermal annealing, as evaluated by spectroscopic investigations of the resulting thin films. The resulting layers are uniform and crack‐free with a thickness of around 150 nm on silicon surfaces. It is shown that such layers can act as boron dopant sources on silicon, sufficient for the fabrication of BCBJ solar cells, as demonstrated by prototype devices.