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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)