Episode 10 – Perovskites, Gold, and 3-D Metal Printing

LASER: Materials Science Podcast

Source: Michigan Tech News

This week on LASER we discuss Perovskite solar cells with organic charge transport layers, the horrible health effects of illegal backyard gold ore refining in Indonesia, and a new free open source metal 3-d printer from Michigan Tech. This show is also the first one we ever recorded entirely over the internet.

1:30 introductions for our first online-only show! (we’ve always done them at least partially in person before.)

3:00 Perovskite Solar Cells Employing Organic Charge Transport Layers. published in Nature Photonics http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2013.341.html

4:00 Perovskite solar cells are important because of their high carrier mobilities (the electrons and holes can more more easily) This is pretty tough to describe in podcast, but Chris gives it a try. A few leading questions help out.

7:00 we want organic solar cells because they can be wavelength tuned and still be transparent, so your windows could turn IR or UV light into energy, while letting visible light pass through.

9:40 we discuss Multi-junction solar cells that are used to overcome the shockley-queisser limit that defines “maximum” solar cell efficiency (~33% for Silicon) https://en.wikipedia.org/wiki/Shockley-Queisser_limit

13:15 Chris’s research is into making a better buffer layer for organic charge transport layers. We trick him into explaining this.

14:45 When are we going to record that special episode explaining photovoltaics? it should be soon…

21:00 after an awkward transition, we end up in Indonesia, discussion small scale (backyard) gold ore refining, and its horrible environmental impacts. From THIS NY Times article http://www.nytimes.com/2014/01/03/business/international/small-scale-gold-mining-pollutes-indonesian-lands.html?partner=rss&emc=rss&_r=1

22:20 we explain the scheme for Mercury amalgam gold ore refining (which was a process used for a few hundred years–we didn’t find a source for the origin)

24:30 Mercury toxin is where the phrase “mad as a hatter” comes from. It also kills people by affecting your CNS, and causes serious birth defects and infertility.

31:00 Chase explains the modern process for Gold cyanidization process. This is a common modern practice for gold ore refinement, started in 1887, and has caused a lot of environmental contamination around California, where it was used following the gold rush. Even with cyanide, it is considered safer than the mercury process.

33:00 we really should have studied our chemistry before describing the process… sorry!

36:30 chase gets indignant about “who needs gold other than scientists?!”

37:00 we should add that “78% of the gold consumed each year is used in the manufacture of jewelry.” (via http://geology.com/minerals/gold/uses-of-gold.shtml)

38:40 Chris didn’t talk much during this because of he was so emotional for the plight of the Indonesians exposed to the mercury.

40:00 Metal 3-d printing! This paper is open source, so its free to read, and it describes how to build their printer! https://www.academia.edu/5327317/A_Low-Cost_Open-Source_Metal_3-D_Printer 10.1109/ACCESS.2013.2293018

41:50 based on the open source reprap 3-d printers (http://www.reprap.org/wiki/RepRap).

43:00 the deposition used is a gas metal arc welder instead of the usual stock extrusion tube.

45:47 the inside areas of the part were much softer than the outside because of the additive manufacturing technique.

49:30 the 3-D printed GUN controversy! (these still wouldn’t hold up to repeated use, so not more useful than a homemade pipe gun)

52:45 we wrap up the metal 3-d printer and our plans for how to use these in the future, and apparently Chris would 3-d print a counterfeit car.

55:00 we’ve joined the AMAZON ASSOCIATE PROGRAM so before you buy anything on amazon, please use our referral link; it won’t change the purchase price, but we’ll get a small portion back.

After the show we talk for a little while about Soylent and its advantages for people working in the lab (How great would it be to be able to work in the lab all the time and not need a lunch break!)

and if you want to offer chase a job, email us a [e-mail]!

Song 1: walkin’ on sunshine
Song 2: burl Ives silver & gold