Light- and power-making things

Inspired by xkcd’s Up Goer Five comic Theo Sanderson created the Up Goer Five Text Editor. It challenges you to explain a hard idea using only the thousand ten hundred most commonly used words in the English language. Lots of scientists on Twitter have been using it to try and describe their work. It’s a lot harder than it sounds! Here’s my attempt:

Many years ago a few people were doing some work and, to their surprise, they managed to make light come out of something that had never had light come out of it before. People were very excited about it and now lots of groups of people spend their time trying to answer questions like “how does it work?” and “how can we make it work better?”. Everyone was interested because they thought it could be used to make new things like better TVs, very small computers and different kinds of lighting. But the perhaps the most important thing it could maybe do was give us all a new way to turn light from the sun into power for not very much money.

At the moment only a few people get to see them because they are hard to make. They are hard to make for lots of reasons, but perhaps the biggest reason is that the parts you need are themselves hard to make. Everyone struggles to make enough of them exactly as they need them to be. If the parts aren’t good enough, sometimes not very much light comes out, or for only a little while, or the ones that turn light from the sun into power don’t do it very well. No one wants any of those.

It doesn’t help that the normal ways of making the parts are often only good enough for making a little at a time. If you try to make more in the same way it stops working so well. I’m part of a group of people trying to make the parts in a new way that can make lots and lots and it still be good enough. In fact, our stuff is usually better than the best stuff you can buy.

I try lots of different ways to make things. I look in books to read how other people did things to get new ideas that no one else has had before. Sometimes they don’t work, but sometimes they do and when that happens it makes me very excited and happy. Sometimes we tell everyone but sometimes we only tell a few people. We can use my new way to make the light-making and power-making things work better and for less money than ever before so everyone can have them.

What do you think?

Put down that bottle of chlorobenzene

Recently I’ve been searching the literature for some good references on the roll-to-roll printing of organic electronics for the introduction of my MRes report, which is due at the start of September.

The performance of organic semiconductors is much lower than that of the conventional inorganic semiconductors. One reason why researchers are interested in organic semiconductors is that they can be produced using printing presses (literally the same technology to print things like magazines, newspapers and T-shirts) so cheaply compared to inorganic semiconductors that it no longer matters that their performance isn’t as good. The biggest application is probably solar cells and it’s really important that costs are kept as low as possible for them to be economocially viable.

Despite being part of the Centre for Plastic Electronics at Imperial, I don’t know of anyone who completely prints solar cells, let alone using roll-to-roll processes. There’s a lot of reasons why (e.g. printing presses take up a lot of space, use a lot of material) but it does my head in that people are use techniques like spin coating and vacuum deposition, anneal at high temperatures in inert atmospheres for long times and use environmentally-unfriendly cholorinated solvents. Papers describing devices made using these techniques frequently laud the scalable and low cost nature of plastic electronics. But are these techniques scalable to large area, high throughput, continuous printing processes? No, not without spending a lot of money, but then it’s not economically viable.

Today I came across a good review[^ref] in Materials Today (open access!) on the roll-to-roll fabrication of polymer solar cells. The first paragraph sums this issue up nicely (emphasis added):

In order to reach its full potential, the imminent realization of the 10 %-10 yr target[^target] within the laboratory must transcend into a realistic industrial process. While this may seem trivial to many and even obvious to some, there are challenges that have perhaps been taken too lightly in laboratory reports. Often tiny spin coated devices prepared on rigid glass through toxic solvent processing and metal evaporation is said to be roll-to-roll and industry compatible. The view held here is that claiming to be roll-to-roll and industrially compatible without such instruments is similar to claiming that one can learn how to swim on a floor.

I love that last sentence so much I’m tempted to quote it at the start of my report.

To summarise: I think researchers need to stop simply writing in the introductions of papers about scalabilty and low fabrication costs and actually start considering it in the lab or, even better, dropping these unscalable techniques and compounds from the lab altogether.

[^ref]: R. Søndergaard, M. Hösel, D. Angmo, T. T. Larsen-Olsen, F. C. Krebs, Materials Today, 15 (1-2), 36-49. DOI: 10.1016/S1369-7021(12)70019-6

[^target]: 10% device efficiency from devices that last >10 years.