Multi-Layer Inkjet Printed Contacts for Si Solar Cells (Poster)

2003

We are developing inkjet printing as a low cost, high throughput approach to the deposition of front contacts for Si solar cells. High deposition rates of 1µm per printing pass were achieved with a new metalorganic ink composed of silver(trifluoroacetate) in ethylene glycol. The printing conditions were optimized to achieve a relatively high line resolution of 120 µm. The optimal parameters for the piezoelectric inkjet were a pulse frequency of 50 Hz and pulse amplitude of 25 V. The best resolution and the line quality were achieved at a substrate temperature of 180 °C and drop separation of 40 µm.

VEYSEL UNSUR. Understanding the solar cell contact formation by digital inkjet printing (Under the direction of DR. ABASIFREKE EBONG)

2005

Ag, Cu, and Ni metallizations were inkjet printed with near vacuum deposition quality. The approach developed can be easily extended to other conductors such as Pt, Pd, Au, etc. Thick highly conducting lines of Ag and Cu demonstrating good adhesion to glass, Si, and printed circuit board (PCB) have been printed at 100-200 deg C in air and N2 respectively.

Digital inkjet printing (DIP) is a precise and promising technology to create fine gridlines for silicon solar cell. It is based on drop on demand (DoD) technology, which drops only when it is properly aligned to avoid wide gridlines. The gridline spreading is controlled by heating the chuck (wafer holder) to 200C at the time of the ink droplets. This eliminates drying step that is common to the screen-printing technology and eradicate gridline spreading. The screen-printed technology (SPT) on the other hand cannot exclude the drying step but relies on the silver loading and organics to balance the paste viscosity and rheology, which are used to control the gridline spreading. The difference between the inkjet and screen-printed inks is the particle size of the paste or ink constituents. While the DIP inks are in the nano-particle range, the SPT counterparts are in the micro-regime. Therefore, understanding the sintering of the nano-particle sizes is needed to achieve low contact resistance and hence high fill factor (FF), which is influenced by the total series resistance of the device. In this paper the microstructural analysis of the inkjet contact system was used to optimize the peak firing temperature for DIP gridlines. The optimized temperature profile found was similar to the SPT. This led to FF of ~79.2% for mono crystalline cell and efficiency of ~19.3% and ~17.4% for multi-crystalline with FF of ~78.5%. It was also found that the series resistance of these cells was not dominated by contact but emitter resistance

2011

Purpose: The aim of the paper was to apply a conventional method “screen printing” using micrometric pastes to improve the quality of forming front side metallization of monocrystalline solar cells. Design/methodology/approach: The topography of co-fired in the infrared belt furnace front contacts were investigated using confocal laser scanning microscope and scanning electron microscope with an energy dispersive X-ray (EDS) spectrometer for microchemical analysis. There were researched both surface topography and cross section of front contacts using SEM microscope. Phase composition analyses of chosen front contacts were done using the XRD method. Front contacts were formed on the surface with different morphology of the solar cells: textured with coated antireflection layer, textured without coated antireflection layer, non-textured with coated antireflection layer, non-textured without coated antireflection layer. The medium size of the pyramids was measured using the atomic for...

2014 IEEE 40th Photovoltaic Specialist Conference (PVSC), 2014

This paper reports a patterning and metallization method for silicon solar cells fabrications. Patterning was achieved by the inkjet printing of a dye-based ink as a mask to protect the photoresist from UV-light initiated crosslinking. The patterned photoresist was used to facilitate the etching of a pattern in the underlying dielectric layer and also to act as a metal plating mask. This method resulted in fine point openings in the photoresist layer with a diameter of 15 μm and line openings with a width of 30 μm. Nickel/copper plated homogeneous emitter silicon solar cells with an efficiency of 18.2% on small size Cz wafers were fabricated using this method, may find applications in the metallization of future heterojunction, rear contact and PERC cells.

Energy Procedia, 2013

Local rear metal contacting through passivating dielectric layers has the ability to increase silicon solar cell efficiencies to over 20%. To-date most contact schemes have involved the formation of localised aluminium-alloyed regions through patterned AlO x or SiN x passivating layers. Recently electrochemically-formed anodic aluminium oxide (AAO) layers have been shown to enhance minority carrier lifetimes of phosphorus-diffused p-type CZ wafers when formed over an intervening layer of SiO 2 or SiN x , suggesting that these layers may find applications as passivation layers for cells. We report here on the inkjet patterning of AAO layers formed over a thermally-grown thin oxide layer on p-type silicon surfaces. The process, which involves the inkjet printing of 50% (w/w) phosphoric acid, was used to form well-resolved arrays of holes with a diameter as small as 20-40 μm in the dielectric stack. Alloying of aluminium, which was evaporated over the patterned dielectric stack, resulted in the formation of localised back surface field (BSF) regions having a thickness up to 8 μm. Future work will focus on adapting this process for use in local rear metal contacting of silicon solar cells.

2014 IEEE 40th Photovoltaic Specialist Conference (PVSC), 2014

2011

In this paper we report on the evaluation of the feasibility of jetting full gridline contacts to fabricate solar cells without additional plating step. We have demonstrated, for the first time, fully ink jetted front Ag gridlines with average line width of only 56.6 μm and height of 30 μm. A high series resistance of 1.1 Ω-cm2 resulted in average fill factor of 0.767 and led to average efficiency of 18.0% on 239 cm2 commercial CZ wafers with sheet resistance of 65-Ω/sq. This result is very promising and leaves room for improvement, especially with optimized finger spacing, improved ink and co-firing process.

1979

Thb report war p n~m d as M account of work sponoorcd by thc United States Government. Neither the United States nor the Uruted States Department of Enetgy, nor any of their employees, nor any of their contractors, subcontractors, or their employees. makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus. product or process disclosed, or represents that its use would not infringe privately owned rights nR1. No. 86/ORO No. SF