More wine

At the banquet today I tried to wines. I tried a cabernet sauvignon, and a chardonnay from some place callled charing hills or something. Both were okay; tasty, drinkable, but not amaazing.

Energy efficiency workshop: day 1, part 2

The fourth speaker of session 1 was Garry Rumbles, a cool guy with a British accent who defended the bulk heterojunction cell. The main message I got from his talk was that the Band diagram is wrong (and therefore that physicists are dumb!). The reason why the Band diagram is wrong is because it hides a lot of the details that are present in molecules, such as the locations of the triplet states, and of various trap states. Also, it doesn't show the fact that holes and excitons annihilate each other. Maybe this is because of the coulombic attraction, although I'm not sure.

He pointed out that the big breakthrough, credited to Alan Heeger, was that you could make solar cells with C60 as an electron acceptor, and with this solar cell architecture you get very slow recombination rates. In P3HT the exciton diffusion time is 300 to 500 ps, which I guess is pretty short, and so the distance excitons diffuse is less than 10 nm. I knew this already. Then he went on to discuss some stuff that was probably important but which I didn't write down and don't recall. Finally, he showed a plot of how a solar cell degrades--it can last for ~50 days, although it seems to have degraded quite a bit by the end of it. He also commented that the most efficient organic cells that have been recently made were made in companies, not in government-funded research labs or universities. And he talked about intrinsic and extrinsic sources of degradation. Extrinsic ones that he listed were oxygen, water, and UV-presumably, they react with the active material, but the material could be protected. Also, there are effects like Delamination, PSS (not sure what this means now but it's in my notes) and Reducing the metal. Intrinsic effects were oxidizing effects, due to polarons (or related to polarons), reducing species, and intermal conversion (which presumably heats up the system and causes thermal damage).

I guess that last point is interesting because internal conversion is the way in which plants dissipate heat, and is deemed "safe" compared to the alternative of a long-lived excited state chlorophyll. I guess heat damage is an issue in things like computers and optical devices, where we need to have chillers and heat sinks. At the same time, plants are probably a lot more exposed to air than computers or laminated (i.e. plastic-enclosed) solar cells, and so they heat from them probably gets conducted away a lot faster. Or maybe there's just less heat to be released. In any case, I wonder where the boundary is between internal conversion=good and internal conversion=bad. Maybe it's not such a good thing in solar cells.

Then he talked about Time Resolved Microwave Conductivity (TRMC) which is this technique that measures charge transfer rates and recombinations lifetimes, I think. I'm not really clear on this but the technique seems cool, and he harped on the importance of considering the triplet state in these calculations, something that I guess solid state physicists don't do. He also mentioned that P3HT has pretty good Intersystem crossing. There was a question at the end about tirplets, and how the are too low in energy to really charge separate.

Which brings us to lunch. I ended up chatting with this guy who works on singlet fission (into triplets). He emphasized the importance of fission rather than intersystem crossing as the desirable mechanism. I guess I had never differentiated these two mechanisms in my mind, so I suppose I should look into that. And at lunch I met some grad students from the Kapteyn Group, who were all cool.

The next talk was about the hydrogen economy. The main point the guy tried to make is that we should only focus our research funding on things that will scale, in time. He doesn't think Carbon sequestration will every become commercially relevant. and apparently crystalling PV cells pay for themselves in 30 years, thin films in 1-2 years, and wind in a few months. And he thinks wind could surpass nuclear energy by 2020. And apparently hydrogen requires 30% of the stored energy in order to generate the fule. But I was a little bored and started doing other things in my notepad.

Then there was a guy who talked about the redox chemistry of water oxidation. I was not really awake, although surely all that is important. THe take home message there was that doing a thorough kinetic analysis of your system is an important thing to do.

And then there was another guy who talked about making photoelectrochemical cells. His main point was that metal oxides are the class of materials taht are most promising. They are stable ("most rocks are oxides") and can be semiconductors. He's doing combinatorial analysis to look for candidate metal oxides, and he's developed modules that can be given to high school students who can help out with this. I thought that was cool, and something I probably wouldn't have liked, at least in theory, as a high school student.

The final talk was by this wonderful lady--she talked about CO2 reduction, but I was tired and learned nothing. But I do remember, either from her talk or the preceding one, that there are catalysts available for making methanol or hydrocarbons out of CO2( without having super-high energy intermediates) but not ethanol--so , that's is a problem for GM potentially.

The poster session was excellent. I learned about triplet fission, and talked to someone who worked on doing 2D spectroscopy with pulse shaping.

Wine Tasting

At the poster session, about which I'll write soon but not now, people were drinking wine. I like wine and the greasy eggplant I had consumed for dinner left me wanting wine, but it cost $6.50 at the bar for a glass, and I didn't want to pay. It looked like maybe some people had these red tickets that got them wine and beer for free, but I especially didn't want to ask.

So after the poster session I walked to safeway, intending to buy some apples and wine. In addition to apples, I ended up getting tea bags, a cucumber, some cherry tomatoes, and some celery. But to my dismay, the Safeway had no wine. So I purchased my produce (And a Colorado mug) and left. Fortunately, a young and probably underage boy who worked at safeway told me that there was a liquor store down the street. So I walked down the street, and shortly I came upon this wine haven called "spirits and wine." The people inside were kind and friendly. I wanted to buy a single bottle and get out, but I also wanted to try something new, but then again I also wanted to get a wine I knew I would like in case the new one was bad. So in the end I got a

Oxford Landing Shiraz, 2006 (South Austrialia) which cost about $7.

and a

Mosel River Riesling, 2007.

The only criteria I had going in was that the wine had to have screw caps, because I don't have any stoppers at the hostel. This turned out not to be too limiting, although it kept me from buying the Yellow Tail Resiling I was going to buy initially, or anything from Sutter Home.

I like the Shiraz, although I wouldn't have a few months ago. I only started liking red wine very very recently--maybe a month ago. It kind of reminds me of the Pinot Noir I had with my grandparents. It's kind of fruity, I think (I guess I don't exactly know what fruity means when it comes to wines, but I use it anyway), not sweet, and has this taste of "I could get really nasty and start tasting like acetone, but right now I'm just pleasantly intriguing and very wine-like."

I would buy it again, and drink it, but I wouldn't tell people that they absolutely must drink this wine if they want their life to be complete.

As for the Riesling:

It is delicious, sweet (but not too sweet, not like the sweet Reisling I had at Suppenkuche on June 29th). It's fruity, and tastes bubbly even though it doesn't actually have bubbles in it.

I would definitely buy it again, although I dont' know for sure that it's the best Riesling I've ever had or anything. I like Riesling a lot.

Other wines that I have had:

Carlo Rossi Sangria: This was my first (maybe second) love, only I learned that if you keep a huge jug for a month it will, eventually, get nasty. Maybe some vintage years are better than others; the last time I had it I couldn't help but admit its less-than-perfectness, even though I still love it because Sangria is Delicious. It is sweet and delicious and like bubbly fruit juice.

Sutter Home Muscato: If Sangria wasn't my first love, this was. It is sweet and fruity and tastes of delicious muscato grapes and is delicous. And cheap. And Delicious.

Yellow Tail Pinot Grigio: I tried it at my parents' house and liked it.

Sutter Home Gewurztraminer: tasty

Some other kind of fancy-pants Gewurztraminer that I had at an italian Restraurant in LA: not tasty, although I didn't admit it to Robert at the time

Some fancy-pats Muscato

Pinot Noir for $16 (one of the Cheaper ones, don't recall the brand): didn't like it at first, but this was the first dry red wine I enjoyed when I had it with my grandparents.

Alazani, a Georgian wine that Borya brought over once: Delicious. And Red. and somewhat sweet.

Cheapo Zinfandel (don't recall the winery--this is why I'm writing these things down!)--pretty good, but not when it's been standing for a month. But good to cook with.

The Brain, it is Full: CU workshop, day 1 part 1

Today was the first full day of this energy efficiency workshop that I'm attending. There were 8 full talks (~45 minutes each) plus a brief introduction to energy policy in the beginning by a guy who works for the Department of Energy, which I didn't really follow too well other than that it seems like the DOE is funding a lot of weapons research and a lot of fuel.

The first talk was by John Benner, who talked about the economics of solar cells. He said that photovoltaics are in a pretty typical "growing curve" in terms of how markets develop, but there will need to be a lot of breakthroughs in order for solar-generated electricity to become cheap enough to be competitive with fossil fuels. Showed some calculations of projected growth rates. He also mentioned that because people have underestimated growth of the solar cell market in their predictions, there hasn't been enough supply of solar cells to meet the demand. Also, that we might be in a "bubble" wrt solar cells, where the cost of the modules is going down, abut the price is not because people will pay. Later, though, there was a discussion about how much energy it takes to make a solar cell; it turns out that you don't get any net energy out of your installation until you stop building new solar cells.

The next talk was by Arthur Frank, from NREL, who talked about dye sensitized solar cells, and about the properties of titania and sensitizers that were desirable for these cells. It turns out that organic molecules are catching up with the more expensive ruthenium based dyes in terms of efficiency. Also, the surface roughness of the titania determines things like charge transport. There was also a comment at the end about trap states in titania, and he said that no one really knows much about traps. Presumably traps are defects in semiconductor structure--at least that's how I always thought about them--but they may not be bad. The person had asked whether there are different kinds of traps (i.e. deep vs. shallow), and whether it's possibly that one kind slows down diffusion and the other kind encourages exciton recombination. And at the end there was a comment about how some Japanese engineers had tested a solar cell for 3 years and it dropped in efficiency by 5%, but this wasn't due to the dye leaking (some dye-sensitized solar cells are made of liquid electrolytes).

Then we had a break. I ate a bagel and some fruit. Then Brian Gregg, also from NREL, talked about small molecules solar cells, and about doping organic semiconductors to improve their performance. The highest efficiency organic solar cell is 5%--not good enough! He talked a little bit about why the conventional band diagram that people use to describe p-n junction solar cells in silicon is the wrong picture to have; how a state diagram is more accurate. Also, unlike Silicon, you can have an open circuit voltage in excitonic solar cells even if your electrodes have the same work function, because you only have hole transport through the material, and not electron transfer. This has to do with the energies of only one of the HOMO or LUMO lining up with the work function of the electrode. There was also something about how you can use chemical potential gradients to help you with your solar cell in addition to electric field gradients, even though you can't do this in silicon. I didn't quite understand that
.
Then he talked a lot about interfaces and the problems with recombination; however, I wasn't sure if he was omitting recombination in bulk because it wasn't important, or because that wasn't what he studied.
He also talked about how In small molecules, the binding energy of the exciton is about 0.25 eV, which is more than the thermal energy available at room temperature (kT). So excitons have to diffuse to an interface and then be split at an interface, in order for them to be useful. But even at the interface the coulombic attraction doesn't go away. There are ways to overcome this, but they end up wasting 0.9 eV, which is a lot. It think this involves some sort of thermal energy, but I didn't understand how it works. He also had a way of overcoming the coulombing attraction energy, but hasn't demonstrated it yet. It involved doping, and he proceeded to talk about the effects of "doping" for the rest of the talk. (Actually, a professor from Maryland who I talked to later and who works on SPM told me that she doesn't think doping is the right term; that really, you're polarizing the molecule differently). But yes, apparently some recent work out of Peter Peumans' group at stanford showed that super-purifying P3HT doesn't actually make a better device--but people don't know exactly what these dopants are.

So Brian Gregg's group has apparently done some "chemical" doping, which increases the dielectric constant of these molecules (the ones he used was PPEEB) and through that maybe increases the mobility (if I understood correctly). And through the Poole-Frenkel equation, which is a super-oversimlification that works, this increases the conductivity.

The next guy was Garry Rumbles, and talked about bulk heterojunction cells, and his talk was cool, so I'll write about that later.

Distopia

Today was the first day of our energy efficiency conference, and Nathan Lewis, a chemistry professor at Caltech, gave the keynote. He is an extremely charismatic speaker and an obviously intelligent man. His talk was very depressing. It was much like watching An Inconvenient Truth, except more scientific. He had a few main points that I've remembered in the hour and a half since the talk ended:
1. There is enough non-renewable fuel to provide 3,000 years' worth of energy
2. But that fuel will dump lots of CO2 into the atmosphere if we use it

3. CO2 is a stable molecule--it doesn't react with oxygen on its own--so it doesn't really break down on its own, ever. It needs a catalyst, like something they use in photosynthesis.
4. There's a lot of energy coming to the earth from the sun
5. But the only way to store it in a way that will scale to the entire world economy is in chemical bonds, i.e. in fuels. Not batteries.

6. If we don't start building solar cells soon, then we (by we he means the world) will build coal and gas plants, because that is "business as usual," and those have a lifetime of 40 years

7. By 2050 we will have dumped enough CO2 into the atmosphere that scientists predict bad shit might go down (or something--I'm not too clear on this part, and I don't think anyone really is) unless we stop emitting now

8. So we better stop emitting CO2 now, guys.

Then Walter Kohn (nobel laureate and creator of the much-despised DFT) suggested that maybe we should try to reduce the world's population. Nathan Lewis replied that that's not very practical; plus, if we were to do that, we'd have to get rid of mostly Americans. Then he answer a question about methane and the meeting was dimissed.

Bouldering

I've arrived safely and soundly in Boulder, Colorado, where I will attend an energy efficiency workshop from tomorrow until Friday. I'm staying at the International Hostel, which is a frat house turned Hostel. I've managed to piss off the front desk guy by being totally clueless about checking in procedures, and by somehow not knowing the code for getting in here after hours--either that, or else he's just not friendly and grouchy. But staying here is inexpensive, my room is clean enough, and the showers, which are basically metal boxes, are going to be a character-building and water conserving experience that will, I'm sure, make me happy to have packed my shower sandals with me on this trip.

I really really liked this town when I first stepped off the bus from Denver. It smells of pine trees. I walked the 0.8 miles to the hostel and was pleased to see people out and about; this seems like a real college town--maybe Berkeley is like this at night, but I don't live in Berkeley. But after I went through the checking in awkwardness here and went for a walk in search of food, I felt a little less in love with the town because I began to feel self-conscious. I wanted food, you see, real food, but most places that were open at this hour seemed to be intended to serve people alcohol. Which is good and fine, except that I don't have anyone to go drinking with right now. I ended up buying a middle eastern chicken wrap from a convenience store where I also bought dental floss and deodorant, and it tasted pretty okay, except that it had all the standard subway sandwich vegetables that add this uniform taste to everything, masking the potential distinctiveness of incredients like chicken and feta cheese. In any case, I got my food, and now I am fed with something more than chocolate-covered esperesso beans. And it is late, and I must go tend to my assigned reading if I am to get what I want out of this workshop.