Optimizing Fine Line Dispensed Contact Grids

Pospischil, Maximilian; Fellmeth, Tobias; Brand, Andreas A.; Nold, S.; Kuchler, M.; Klawitter, M.; Gentischer, Harald; König, Markus; Hörteis, M.; Wende, L.; Doll, O.; Zengerle, Roland; Clement, Florian; Biro, Daniel

doi:10.1016/j.egypro.2014.08.046

Cited by 14 publications

(11 citation statements)

References 5 publications

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“…[35,36,42,43] Fraunhofer Institute for Solar Energy Systems (ISE) developed the method and apparatus for DIS metal grids for solar cell applications and works constantly on improving the DIS technology for over more than ten years. [36,44,45] The metal paste is extruded through narrow openings smaller than 60 μm, either single nozzles or print heads with up to 130 nozzle openings are used, whereby multinozzle print heads are normally used to obtain the industrial needed throughput. [36] In 2019, the Fraunhofer spin-off HighLine Technology GmbH was founded with the goal to commercialize a multinozzle print head for the parallel DIS technology.…”

Section: Dispensing Technologymentioning

confidence: 99%

CIGS Mini‐Modules with Dispensed Metallization on Transparent Conductive Oxide Layer

et al. 2020

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This article presents the application of a parallel dispensing device for low‐temperature silver paste metallization on transparent conductive oxide (TCO) layers of Cu(In1 − xGax)Se2 (CIGS) substrates as an alternative metallization technology to screen printing and inkjet printing. A curing variation experiment is performed to analyze the effect of different curing conditions on the resulting contact resistivity of the metal grid. Contact resistivity values below 5 mΩcm2 are achieved. Furthermore, CIGS mini‐modules are metallized with three different low‐temperature paste formulations obtaining a record core finger geometry of 25 μm and an average optical aspect ratio of 0.46 using 25 μm nozzle openings. The dispensed metal grid on the TCO layers achieves the comparable current density values of jsc = 32.2 mA cm−2 and the open‐circuit voltages values per cell of Voc = 672 mV as the screen printed metal grid on CIGS mini‐modules and, hence, a nominal power of 2.05 W. The metal grid enables the use of broader cell widths compared with grid‐free CIGS samples and results in a reduced dead area.

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Section: Dispensing Technologymentioning

confidence: 99%

CIGS Mini‐Modules with Dispensed Metallization on Transparent Conductive Oxide Layer

et al. 2020

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“…Keeping in mind that the fill factor loss of frontside grids on such textures can be minimized or completely avoided by certain means, the benefit is even higher. Such means are the optimization of the grid design (number of contact fingers) [18] or a double printing step to increase the finger height and thus reduce lateral finger resistance R L [19].…”

Section: Discussionmentioning

confidence: 99%

Impact of Texture Roughness on the Front-Side Metallization of Stencil-Printed Silicon Solar Cells

Lorenz

Strauch

Demant

et al. 2015

IEEE J. Photovoltaics

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Realizing narrow contact fingers with low lateral resistance is a major goal for the front-side metallization of silicon solar cells. The formation of screen-or stencil-printed contact fingers is governed by a variety of influencing factors. One of these factors is the surface roughness of the textured silicon wafer. However, only a few investigations have been carried out to investigate this impact in detail. In this study, the influence of arithmetical mean roughness R a of four differently textured wafer surfaces on contact finger geometry and lateral finger resistance, as well as optical and electrical losses, has been investigated. It will be shown that texture roughness has a considerable impact on the properties of the front-side grid. Narrower contact fingers could be realized on the smoothest texture, leading to a current density gain of Δj sc = +0.27 mA/cm 2 . On the other hand, increasing texture roughness has affected the amount of transferred paste and, thus, has led to a lower lateral finger resistance R L . Thus, contact fingers on the roughest texture have benefited from a fill factor gain of ΔFF = +0.24 % ab s . A sensitivity analysis of both impacts has shown that the current density gain has overcompensated the fill factor loss. Thus, textures with a small roughness are beneficial with respect to the formation and electrical properties of stencil-printed front-side grids.

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“…The electrical aspect ratio AR el was calculated by Equation (11), allowing to quantify the electrical grid performance by including the conducting and contacting area [ 46,47 ]

\begin{matrix} {AR}_{el} = \frac{A_{cross}}{w_{shading}^{2}} \end{matrix}

…”

Section: Methodsmentioning

confidence: 99%

The Link between Ag‐Paste Rheology and Screen‐Printed Solar Cell Metallization

Tepner

Wengenmeyr

Linse

et al. 2020

Adv Materials Technologies

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printing machine technology with the goal of continuously increasing production throughput while improving alignment precision. Additionally, further paste development is conducted to enhance printed line geometry and contact formation. Over the last 15 years, screen printing of Ag-pastes for Si-solar cell metallization has become a success story by decreasing the printed electrode width from ≈120 µm in 2007 reported by Mette [2] toward only 20 µm reported by Tepner et al. in 2020. [3] Therefore, flatbed screen printing is catching up with other fine-line printing approaches for solar cell metallization. Recent studies reported finger widths down to 17 µm by using the parallel dispensing approach [4] and 20 µm by using pattern transfer printing. [5] Both results demonstrated homogenous line widths at competitive printing speeds. These achievements of screen printing have their origin in the continuous efforts of the industry around metallization to improve their technology and products and the scientific community providing an in-depth insight into the underlying physics around that topic. Over the years, the latter provided various research studies, focusing on understanding the impact of paste rheology, [6-10] optimizing the electrical performance of Ag-contacts, [11-14] and the impact of screen design on printing results. [6,15-19] Commonly available Ag-pastes for front-side PERC are highly filled suspensions containing up to 95 wt% spherical Ag-particles with diameters below 5 µm. [2,20] They show non-Newtonian flow characteristics with strong shear thinning behavior after exhibiting significant yield stress. [21,22] A fast and reproducible screen printing process imposes a few crucial requirements on the rheology because the paste is first excessively sheared when being transferred through a fine mesh. [23] Afterward, it is further pushed onto the substrate through the screen opening width w n and the height EOM (emulsion over mesh). During this motion, shearing should already be minimized because the recovery of the zero shear viscosity is highly time-dependent (thixotropic behavior). [6,24] Usually, this minimization of shearing within the screen opening is achieved by the paste's ability to slip at the emulsion surface. This effect has been the focus of several research studies, which showed how slip effects are enhancing screen-printing performance. [25-27] After the paste has been pushed through the screen opening onto the substrate, the Today's photovoltaic production chain is moving into a material crisis as the use of silver for front-side metallization of passivated emitter and rear contact solar cells remains a crucial requirement. The shared effort of the scientific and industrial community to further reduce Ag-consumption as much as possible without compromising cell efficiency has become more challenging in recent years. Further improvements require a deep understanding on the paste-screen interaction at narrow line widths. This study presents the impact of Ag-paste rheology on fine line screen ...

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Optimizing Fine Line Dispensed Contact Grids

Cited by 14 publications

References 5 publications

CIGS Mini‐Modules with Dispensed Metallization on Transparent Conductive Oxide Layer

CIGS Mini‐Modules with Dispensed Metallization on Transparent Conductive Oxide Layer

Impact of Texture Roughness on the Front-Side Metallization of Stencil-Printed Silicon Solar Cells

The Link between Ag‐Paste Rheology and Screen‐Printed Solar Cell Metallization

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