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Welcome Dr Sam Stranks, entrepreneur and professor at Cambridge University!
- Perovskites
- 0h 0m 49s
- The family is based on the crystal structure
- 0h 1m 15s
- Have been worked on for 2 to 3 decades
- 0h 1m 44s
- Only since 2009 have they been used as a solar cell
- 0h 2m 36s
- Sam’s background is physicist
- 0h 4m 46s
- Raised in Australia
- 0h 6m 23s
- Broad undergrad background
- 0h 7m 0s
- Bridged chemistry and physics in Master’s program
- 0h 7m 22s
- Worked on removing white wine proteins
- 0h 7m 32s
- The mechanism is similar to how alzheimers blobs together
- 0h 8m 50s
- 2007
- 0h 10m 24s
- He got a Rhodes scholarship which meant he ended up going to Cambridge University.
- 0h 10m 29s
- Research included carbon nanotubes
- 0h 11m 7s
- Wrapping polymes around then
- 0h 11m 21s
- Popularity has been dropping
- 0h 11m 47s
- Fullerenes, Graphene both won Nobel prize.
- 0h 12m 2s
- Producing nanotubes is difficult
- 0h 12m 21s
- Dave made a video about a bunkum Kickstarter doing Graphene heaters
- 0h 12m 34s
- Specifically separating out metallic and semiconductor types
- 0h 12m 47s
- Finished PhD 2012
- 0h 15m 5s
- Joined Henry Snaith‘s group doing dye sensitized solar cells
- 0h 15m 21s
- Reemergence of perovskites
- 0h 16m 21s
- The initial focus was on a dye sensitive cell made out of perovskite
- 0h 18m 25s
- Early efficiency was 3%
- 0h 18m 56s
- The research is done in a place that looks more like a chemistry lab than a semi lab
- 0h 22m 23s
- Solar simulator to replicate the sun
- 0h 23m 40s
- How are perovskites different from solar cells?
- 0h 25m 34s
- Silicon has an indirect bandgap
- 0h 26m 49s
- Multijunctions cells (the kind on satellites) have different absorbers (different colors)
- 0h 27m 52s
- Record silicon efficiency is 27%
- 0h 28m 21s
- Full panel is about 20%
- 0h 28m 39s
- Perovskite is at 23%
- 0h 29m 5s
- Triple junction is 39%
- 0h 29m 27s
- Videos from past guests Sam Zeloof and Jeri Ellsworth
- 0h 30m 53s
- Printed solar cells
- 0h 32m 4s
- ABX3
- 0h 34m 4s
- Thickness only needs to be half a micron
- 0h 34m 41s
- The name ‘perovskite solar cell’ is derived from the ABX3 crystal structure of the absorber materials, which is referred to as perovskite structure. The most commonly studied perovskite absorber is methylammonium lead trihalide (CH3NH3PbX3, where X is a halogen atom such as iodine, bromine or chlorine), with an optical bandgap between 1.5 and 2.3 eV depending on halide content. Formamidinum lead trihalide (H2NCHNH2PbX3)
- 0h 35m 56s
- Currently using Indium for the contact, but it’s hard to get, running out
- 0h 36m 13s
- Talking through the stack
- 0h 37m 12s
- Bottom electrode is Indium Tin oxide
- 0h 37m 37s
- Then a layer of perovskite
- 0h 37m 53s
- Top layer is organic
- 0h 38m 37s
- Illumnate through the glass,
- 0h 39m 33s
- InSnOx is transparent up to UV
- 0h 41m 14s
- Perovskite absorbs 200-800
- 0h 41m 28s
- Using lasers to test with pulses
- 0h 44m 57s
- Pulses for a 1 ps
- 0h 45m 7s
- Monitor how they recombine and lose energy
- 0h 45m 38s
- What causes a defect?
- 0h 46m 23s
- What actually makes electrons mobile in the ABX3 structure?
- 0h 49m 15s
- Structure is mostly from the B and the X (lead and iodide)
- 0h 49m 35s
- Covalently bonding vs ionic bonding
- 0h 52m 35s
- Other applications being targeted
- 0h 56m 47s
- Light emission (LEDs)
- 0h 56m 57s
- Also using for lasing materials (LASERs)
- 0h 59m 41s
- Want to make an electrically pumped laser
- 0h 59m 55s
- Have been some changes in the A site that stabilize ion migration
- 1h 1m 55s
- Sam is a founder of Swift Solar
- 1h 2m 29s
- The 6 founders had spent time together in Henry Snaith’s group
- 1h 2m 43s
- Focusing on making tandem cells
- 1h 3m 20s
- Making a solar sheet
- 1h 4m 13s
- More solar cells in a smaller area
- 1h 4m 59s
- Payback periods
- 1h 5m 25s
- Why hasn’t this started on the production side yet?
- 1h 6m 18s
- Solar is coming down to 20 cent per watt
- 1h 6m 43s
- Install costs are still $1 per watt
- 1h 6m 56s
- The lightweight aspects lowers the cost of installation
- 1h 7m 20s
- Sam did a TED talk
- 1h 8m 13s
- Integrated photovoltaics
- 1h 8m 25s
- Group web page
- 1h 9m 27s
- Want to learn more about bandgaps? Check out pveducation.org
- 1h 9m 33s
- Scientific American wrote an article about The Perovskite Boom last year
- 1h 9m 54s
- Sam’s lab is taking new students! Reach him via his web page or reach out to him on Twitter (@SamStranks)
- 1h 11m 59s
Photo: Ryan Lash / TED
Eyy I researched perovskite solar cells during my year of postgrad study. Two key things I think the Sam should have gone into more detail about:
1. Their stability is much worse than your standard silicon based solar cell, even if you make a super good seal to keep moisture out from what I recall they still degrade after a month or two (20% drops to 15% and so on)
2. They have really interesting IV curve behavior in that if you scan from 0V -> OC voltage when characterizing them you will get a lower peak efficiency than if you were to scan from OC -> 0V. I don’t think anyone has given a full answer as to why but it seems to do with the formation of temporary dipoles when doing a reverse scan. Anyway, what this means is when someone says they have a perovskite solar cell that is 25% efficient you need to ask how they did the IV scan, because you might find that its 20% in one direction and 25% in other
Also big thanks for Chris & Sam on this episode, was really interesting to hear how the progress of perovskites is going since I last looked at them a few years ago
Great information here! I think that the kind of “forward vs reverse efficiency” is an interesting point as to why these aren’t ready for prime time yet. Thanks!