New Batch Reactors for Solar Cell Passivation from Picosun

Published on April 11, 2011 at 2:03 AM

Picosun Oy, Finland-based global manufacturer of state-of-the-art Atomic Layer Deposition (ALD) systems has launched production of fully automated high volume throughput batch reactors for crystalline silicon (c-Si) solar cell surface passivation. In the wake of the trend of constantly growing market and installation figures for solar power (35 % - 40 % annual global market increase for several consecutive years already) 2011 has already been dubbed "the year of solar energy".

At the same time, coincidentally enough, 2011 has been predicted to become the year of major breakthroughs for many industrial scale applications of ALD. Picosun's SUNALE P-series fully automated batch reactor represents a prime implement for these applications - fast and cost efficient high volume deposition of efficiency improving thin film structures for c-Si solar wafers, destined to change the markets for what is possible for solar cell manufacturing.

In the photovoltaic (PV) industry, ALD has tremendous potential for performance improvement for all types and generations of solar cells. Especially the newer PV technologies based on e.g. dye, organic and thin film structures are in dire need of panel efficiency and lifetime improvement with simple, upscaleable and cost-efficient ways. ALD coated thin films in strategic locations of the cell/panel can reduce recombination, block impurities and/or harmful substances penetration into the cell, work as a corrosion protection or encapsulant and replace poisonous or expensive cell materials.

Despite the boom of new solar cell technologies during the last couple of decades, c-Si is still the global leader in cell materials, comprising over 80 % of all installed PV power today. Superior efficiencies have been measured with c-Si cells passivated on the front side with ultra-thin ALD Al2O3 layers. This is due to negative fixed charge at the interface with silicon, which leads to low surface recombination velocities. With also backside passivation with ALD Al2O3, on the other hand, over 1 % absolute efficiency improvement and 6 % relative efficiency improvement have been measured due to the so-called "localized back surface field" effect.

Picosun's Managing Director Juhana Kostamo is happy: "Our extensive knowhow on ALD and experience on numerous ALD tool prototypes tested throughout over the last three decades have been the necessary key for designing a fast and reliable batch ALD tool enabling high throughput and low particle count on a vast number of samples."

"This generation of novel fully automated batch ALD tools is already in the process of changing the economics for ALD mass production in the PV industry," Kostamo says.

Within the global clean and sustainable technology and renewable energy community, Picosun participates actively in several international, European Union (7th Framework Programme) funded research projects such as the ROD_SOL project, where ALD is a central process step in the manufacturing of novel high efficiency Si nanorod solar cells, the next chapter in environmentally sustainable production of thin film solar cells.

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