DEK Solar Blog

Repeatable accuracy? Read ‘more efficiency’...

From time to time, the good folks at Circuits Assembly magazine ask me to write a column for them highlighting my thoughts on current industry issues. And because each of these tends to focus on something I’m passionate about, I’ll always try to convert these articles into blogs to keep you posted on what I’m thinking about when it comes to our industry. Assuming you’re interested that is! Well, here goes; the first in this series is on the subject of accuracy – something I know which is close to all of our hearts.

One of the main issues facing the solar industry is cell efficiency. I’d confidently go so far as to say it’s key to solar’s medium and long-term success since it directly impacts on cost per watt. Now, here comes the science: over 90% of PV cells are based on silicon wafers, onto which light harvesting capacity is built using diffusion techniques. On top of this, a grid of silver energy-collecting “fingers” and bus bars is printed to route energy off the cell.

That’s where our first challenge comes into play. Given that current industry practice is to print all of these features on the light-gathering side, they effectively shadow the underlying silicon substrate, rendering that real estate incapable of doing what it was designed for.

One obvious route to increased cell efficiencies is to give finer lines more height, but the physical properties of printing screens, and the release properties of standard silver screen printing pastes, effectively put a maximum height on 50-60µm lines of about 15µm. “Not good enough!” I hear you say. Agreed. So, one of the ways around this is to print the lines twice over, in a Print-On-Print process that effectively doubles grid height, and therefore its current-carrying capacity. Everyone’s a winner.

Providing they do it right, of course. As we know from our experience with this procedure for the semiconductor and biomedical sectors, repeatable accuracy is the key here. Mainly because without it, this fine line work would simply be impossible. Consider too that a high definition screen print relies on an effective gasket between the substrate and the underside of the print screen, so alignment must be perfect.

Wherever you look in the solar cell and module assembly industry, repeatable print alignment accuracy is at the heart of efficiency. If solar energy is to become a widely available, cost-effective alternative energy source that excels on its own merits, efficiency must increase while material costs and the cost-per-watt needs to be driven down. Which is why efficiency is at the heart of our PV3000 metallization platform! It’s also why we’re edging closer to grid parity every single day. See you there!

- Darren Brown, Alternative Energy Business Manager.

 

 

A tale of two expos; Karen’s diary from SNEC…

Following Darren’s blog observations about solar expos last week, I thought I’d write the next chapter of this story from my view – here in Shanghai for the SNEC PV Power Expo. Of course, this story is a tale of two expos since the event clashes with the small matter of the World Expo – only the largest and most expensive World’s Fair ever. So, as you can imagine, in addition to the issues surrounding an intensive event calendar, there were also concerns about attendance at the PV show, appearing as it does in the shadow of this city’s mammoth enterprise. I’ve kept a diary since I’ve been at the show so I can share the highlights with you. Here goes…

My epic journey…

As a frequent traveller to Shanghai – a city that I love to visit – I’m used to how efficient the immigration and custom processes are. So, it was a little surprising to come across lengthy queues at passport control. Customs, usually a mere formality of walking through ‘nothing to declare’, has now introduced X-ray machines to screen all baggage before you can exit the terminal. For those of you who travel I am sure you can picture the scene! The reason? Expo 2010 – more on that later. But it wasn’t all travel trauma; I had an excellent flight and since the plane was only half full, it was a little surprising that I didn’t see the Company Chairman, John Knowles, sitting a few rows behind me until half way through the flight! Good job I was behaving myself then :-)

Day one...

The day started off badly. After two days' local holiday in celebration of the opening of Expo 2010, it took an hour to travel 20km from the hotel to the Pudong Exhibition Centre via the Yan'an tunnel.

Anyone who’s ever travelled in Shanghai will understand the chaos of travelling by road – made worse by torrential rain, temperatures in the high 20s and high humidity. On arrival at SNEC, there was more queuing as everyone was security checked.

Day one was positive - consistent visitors to the booth of both existing and potential customers. For me, the only drawback was that the air conditioning broke down late morning and it became very uncomfortable as the day progressed. To put it into perspective, Joe from Heller told me that the temperature on his oven indicated 38 degrees – no wonder we were all sweltering! 

Nevertheless, we all agreed it had been a good day with excellent machine demos as well as customer discussions and press interviews. On the DEK stand, discussions centred mainly around issues such as net throughput, inspection, differences between our PV3000 and PV1200 metallization systems, available options, how to minimise downtime, our stencil offering – the list goes on!

And on a political note, I found that the press were very interested in current discussions on Europe wanting to restrict import of wafers produced in China. You may remember John referred to this in an earlier blog. China’s stance is clear; they will not restrict the import of equipment from Europe, Good for them for taking the long term view I say.

Day two…

Glorious sunshine, a little less humidity and only 30 minutes to get to the show – yippee!!  But, I’m feeling good as I had an extremely relaxing evening after a hectic day at the show – an excellent foot massage combined with a full night’s sleep. I’m convinced one influences the other! Today has been very busy, lots of visitors to the booth and excellent discussions. It was great to see so much interest in our screens technology. Max from our Singapore Stencils Manufacturing Centre has done an excellent job explaining how screens and stencils can significantly impact good prints.

And, as an added bonus, government-owned China Central Television (CCTV) interviewed us at the show! They identified us as one of the top exhibitors at SNEC and quizzed our team about our history and technologies. After the interview airs, we’ll post the video – so watch this space!

A final thought…

Despite initial misgivings, the World Expo did not take the shine off SNEC. Furthermore, the success of SNEC proved its worth and showed that the right event in the right place can attract a quality and quantity of visitors. This was a good show and it was rewarded as such. However, the argument about scheduling – going back to Darren’s previous point - is not likely to disappear any time soon…

And as for the Expo? It’s come a long way since it opened in London in 1851! The Shanghai Expo opened with 220,000 people visiting on the first day. Be warned – it’s busy inside and queues are around three hours long. I’ve got a ticket but won’t manage to attend during this trip – I have plenty of solar work to keep me busy for now!

- Karen Moore-Watts, Global Marcom Director

P.S. See below for a photo of our very own Daniel Chang being interviewed by CCTV!