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High throughput manufacturing micro to pico-liter 3D conformal dispensing systems and
laser micro machining tools customized for your needs

Solar Cell Metallization High Speed Dispense Solutions

nScrypt direct print front side solar cell metallization example. Photo of nScrypt direct print solar cells

nScrypt has achieved a new standard in front side solar cell metallization through direct print technology and continuous collaborations with several key solar industry partners. nScrypt's patented SmartPump™ and non-contact direct print micro dispensing, create high aspect ratio conductive lines that provide a demonstrable efficiency gain. This gain in efficiency translates directly to a $2-3 million annual benefit for solar cell manufacturing plants.

Through a unique parallel printing process, multiple lines and bus bars can be printed at speeds exceeding that of screen printing. A modified commercial screen-printable silver paste is used to pattern the metal lines directly on the top-side of wafers using a process whereby the line width, pitch, and height can be carefully controlled. In a typical case, the line width is as small as 50 microns by 30 microns tall after firing. This is typically more precise than stencil printing, which generally can only achieve dimensions around 110 to 130 microns width. This type of printing effectively reduces the shading area while maintaining high grid line conductivity and low contact resistance.

Direct Print Clearly Shows Advantage Over Screen Print

Direct Print Process More Efficient

Precise Lines from nScrypt Machines

Optical image of the non-contact direct print finger line top view with micron scale.
Scanned electron microscope (SEM) photo of non-contact direct print finger line top view with micron scale shows a more narrow line with a higher aspect ratio and is thus more efficient.

Optical image of non-contact direct print finger line cross section.
SEM photo of non-contact direct print finger line cross section with micron scale shows a higher aspect ratio and thus is more efficient.

Screen Print Process Less Efficient

Screen Print Has Lower Aspect Ratio

Optical image of screen print finger line top view showing lower aspect ratio.
SEM photo of the screen print finger line with micron scale shows a wider line.

Optical image of screen print finger line cross section showing lower aspect ratio.
SEM photo of the screen print finger line with micron scale shows lower aspect ratio.

Key Features

  • $2-3 million annual savings can be realized in solar cell manufacturing plants by using nScrypt printed conductive line techonologies.
  • Solar cells with direct print gridlines show up to a 0.5% absolute efficiency increase over those with screen print gridlines.
Zygo image of the more efficient higher aspect ratio non-contact direct print finger line. Zygo image of nScrypt's advanced technology to produce high aspect ratio finger lines

Disadvantages of Screen Print

Metallization is one of the key components for the manufacturing of high efficiency solar cells. Screen printing has been the dominating technology for this process, which is becoming the challenge for next generation solar cells. There is a trend to make thinner cells, since the price of the base material (poly silicon) is increasing dramatically. Screen printing, as a contact process, tends to break cells, thus reducing the throughput as well as the yield. Another drawback of screen printing is the limitation for narrower lines, which is the target for the photovoltaic (PV) manufacturers.

Enabling Higher Solar Cell Efficiency

There is a great need to develop a non-contact technology to produce lines that are 60-80 microns and have a high aspect ratio. To solve this problem while maintaining high throughput, nScrypt Inc. has developed high speed dispensing technology for the solar cell metallization process. This is achieved through non-contact, through-nozzle dispensing.

The nozzle (tip) has been optimized to a conical shape which reduces the pressure needed to extrude highly viscous conductive pastes, thus increasing the flow rate at the same pressure level (as compared to standard tubing tip). This technology makes high speed printing possible, and it can handle materials up to several million centipoises in viscosity. A number of PV materials have been dispensed at several hundred mm/second.

Parallel dispensing tools further enhance speed. The SmartPump™ technology, which employs a special needle valve mechanism to control flow starting and stopping coupled with the high speed ensures material is accurately deposited and placed (x, y, z). The needle valve technology enables pico-liter level control in the dispense process.

Tools, software, and processes are integrated into nScrypt's machines, enabling micro resolution 3D placement. Cell efficiency is noticeably increased versus that of cells printed by screen printing, provided everything else is the same. The material nScrypt uses in its solution is a modified version of the commercial screen print paste.