We met with Dr. Gregory Scholes to discuss photoexcited molecules, phone systems, future technologies, and much more. Enjoy!
Princeton University Professor Dr. Gregory Scholes describes how he became a chemist and traveled to various universities before eventually landing in New Jersey. Dr. Scholes discusses his work in photochemistry, a field which he has seen evolve from simple OLEDs to intricate television systems. He discusses how the efficiency of systems used in our phones has dramatically increased. Dr. Scholes’s lab studies what happens in a photoexcited molecule which is enabling the development of future technologies. Follow along as William S. Tod Professor of Chemistry at Princeton University and Deputy Editor for the Journal of Physical Chemistry Letters talks with Dr. Jed Macosko, academic director of AcademicInfluence.com and professor of physics at Wake Forest University.
95% of the time, it will reach the end zone where it will for instance split water ultimately, without being dissipated. And so, this is remarkable in nature and it takes us much longer to produce technology that, so efficient as this.” – Dr. Gregory Scholes
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(Editor’s Note: The following transcript has been lightly edited to improve clarity.)
Jed Macosko: Hi, this is Dr. Jed Macosko at Wake Forest University and Academic Influence. We have today here, Greg Scholes from Princeton University, who’s a famous chemist and originally from Australia.
So tell us, Greg, how did you end up going from Australia to the University in New Jersey, Princeton? What was that trajectory like?
Greg Scholes: Yeah, it was around the world trajectory, I would say. So at the time, there was less information on the internet, email was new and so on. It wasn’t that long ago, by the way, that this was the case.
But the typical route was I’m an Australian, I should go to England. And so I did that for a post-doc at Imperial College, and it was there that I met Graham Fleming from UC Berkley, and ended up doing a post-doc with him.
So then I went from London to Berkeley and from there University of Toronto for my first faculty position. I was 14 years as a Canadian. And more recently, I moved to Princeton, New Jersey. So there’s the route.
Jed: That’s really fun to hear about, your different stops along the way.
Did you also do your PhD in Melbourne?
Greg: Yes, that’s right. My PhD was in Melbourne.
Jed: Wonderful, so you really went all around, and it did seem like that first research project that you did as an undergraduate got you hooked on the idea of the exploration.
What was that first research project that you did?
Greg: It was actually photochemistry or photo-physics of these fascinating molecules where there were two light-absorbing molecules typically tethered by a chain, and we wanted to study how they interacted after absorbing light.
…I had no idea what the project was about. But he was so excited, I figured it must be good.” – Dr. Gregory Scholes
But I knew nothing about molecules absorbing light or the experiments that were to be done or anything. I just remember the post-doc who explained the project to me.
He filled a blackboard with drawings of potential energy surfaces, molecular structures, and goodness knows what. And at the end of it, I had no idea what the project was about. But he was so excited, I figured it must be good.
Jed: That’s great.
Was it fluorescence residence energy transfer between the two die molecules or was it just... What were you studying?
Greg: At that point it was not, it was a precursor to that. There was a photochemistry, actually, a reaction where when you excite one-half of these systems which they can form a sandwich and come together and form chemical bonds between them. And it was to study that, and there was some pretty interesting molecules, and they form these butterfly molecules at the end.
Jed: Oh, cool. That is so cool.
Well, now, what are you working on that might have application to sort of the average Joe on the street?
Like you mentioned OLEDs and quantum dot screens.
What role have you had in some of those developments?
Greg: Yeah, I think that that would be helpful, for people to understand where does this technology come from. Because it wasn’t so long ago; I remember going to a conference, maybe it was 2002.
And at this conference, there were people speaking and then they would bring out a little piece of plastic in a battery, and wire that piece of plastic to the battery and it would shine bright orange, and it was an OLED. And how far have we come now? We have the TVs that work on this.
But the point of the story, I think, is that even though there was this device that had been discovered, it was very far from being able to go to market. And there was all sorts of quite technical scientific questions that people had to wrap their head around. And if you like, I can give a quick example of one.
Jed: Sure, especially as it pertains to your research, ’cause we wanna get to know you in your lab. So go ahead.
Greg: Yeah, okay. Well, I assume you’re editing this. I think it’s a good example for the general public, we work around this area, but not specifically on it, but should I still...
Jed: Go for it, yes.
Greg: So one of the issues with these systems is because of some statistics in quantum mechanics; already sounds complicated, turns out when you inject charges into the plastic and the two charges, the plus and minus, come together in a particular way at a center that will eventually emit light, a molecule, only one time out of four can they come together in such a way that they can emit that light. And so the efficiency of the device was low. It was not comparable to what else we could do in technology at that time.
And so that had to be overcome, and the way that it was overcome that’s used now, I think in your iPhone, was to flip the whole story on its head and to say, "Well, what if we could get light out of the three-quarters of those, they’re called re-combinations, that are dark in this plastic that I told you about."
And the key was simply to say, "Okay, we can do that, if we take a different material that instead of being dark, three-quarters of the time it’s bright three-quarters of the time and dark one-quarter of the time." And it was those molecules that were prepared that changed the technology.
Jed: That’s great.
So the ones that are in our phone right now work three out of four times, whenever there is a combined charge?
Oh, that’s... Wow, that’s great. So it increased the efficiency by a factor of three just by using a different kind of material.
Jed: Wow, fascinating.
Now again, how does your lab relate to all this? ’Cause we know you’re one of the most famous influential chemists, according to our algorithm, and we know you’ve been doing amazing things, but what is that kind of stuff you’ve been working on?
Well it turns out… that energy can jump between the molecules and it can jump thousands of times before that light comes back out.” – Dr. Gregory Scholes
Greg: Yeah, so there’s all sorts of processes that happen once you have light or charge, but let’s talk about light in a complex material. And so this could be in the proteins that capture light in photosynthesis, it could be in these plastics that emit light and it’s called, when you have this photo excited molecule, what does it do?
Well it turns out it that energy can jump between the molecules and it can jump thousands of times before that light comes back out. And this is important in the OLEDs, because if that excited state encounters a quenching site, what’s called, some kind of impurity that takes the energy and just dissipates it as heat, then the device will be inefficient.
In fact, the jumping of the energy, called energy transfer, is so effective that those impurities would dominate what happens.
In photosynthesis that would also be a problem. So in photosynthesis, one needs to absorb light in any of the chlorophylls, there’s hundreds of them around the enzyme that needs to be sensitized with the energy from that light and that energy will jump from molecule to molecule. It’s hard to imagine on this scale, of the molecular scale, in these proteins but it will jump thousands of times and 95% of the time, it will reach the enzyme where it will, for instance, split water ultimately without being dissipated. And so this is remarkable in nature and it takes us much longer to produce technology that is so efficient as this, but I study how this happens.
Jed: You study the jumping or how it’s quenched? Which part do you mainly focus on?
Greg: All of them are similar processes, I have to say, but I do focus on the jumping. For instance, how quick can these jumps be? What limits how far you can go? Can you bring quantum mechanics into play to make these systems more efficient? If so, what does that look like? How can we understand it? It’s these kinds of questions.
And when you say bring to bear quantum mechanics, do you mean quantum mechanical simulations done on computers to try to figure out how to make it more efficient or what did you mean by that?
Greg: So we do indeed use quantum mechanical modeling to study this in order to get... What that does is it takes experimental data, which is somewhat abstract of course, unless it’s done in the lab, and it relates it to what might happen if we drew pictures showing all the molecules and the atoms, and that’s the importance of that.
And that enables us to make these quantitative comparisons across the scales. Questions, there’ve been questions for many decades about the precise mechanism of many of these fast processes, electron transfer, this energy transfer.
The questions being, does it really happen, as I said, like a random jump of processes or it could there be some interesting correlations that make it a bit more challenging to work out or to be able to predict how these systems work and how to optimize them. And that’s where quantum mechanics can come into play.
Jed: That’s great. Well, I’m sure that your students really get to know the systems that you’re looking at. Each one is, I’m sure, very different.
Have any of the systems you’ve studied made it into commercial uses, or do you study ones that other people have found to be useful in commercial uses, and you study them? What’s the relationship between what you and your students have done and what went to market?
Greg: I think most of what we study is fundamental. It’s enabling, in many times, future technologies in the sense that there’s a lot of work that has to be done in the trenches ahead of time before something can become a device.
As I said, there’s a lot of questions, a lot of problems that you need to clean up. Like I said, there’s the LEDs. Nevertheless, we have worked also on some materials preparations and just for other reasons, and these have been patented and I think commercialized.
Jed: Very cool. Well, it is true that there’s so many basic fundamental questions that need to be resolved.
And what would you say was the most exciting one that you and your lab figured out that you’re like, "Wow, now the world knows that this is how it works." Is there one that you can share with us today?
…the value of this basic research is that, is discovering something that you never could have imagined would have been there. It doesn't have to be super complicated, but just surprising.” – Dr. Gregory Scholes
Greg: Probably not, to be honest that are of interest to most people. I think the thing about... Oftentimes what happens in science is that the work that you’re most excited about, if you zoom out, it is pretty specialized and that your appreciation for why it matters and why it was a big achievement is just because you’ve studied that problem for so long, decades maybe, even at the perspective that this is an important problem to resolve or important observation to make.
So we’ve done many, I would say our group has done a lot of experiments that have shed light on things we could never have predicted and certainly didn’t initially understand, maybe this is more interesting in the value of this basic research is that, is discovering something that you never could have imagined would have been there. It doesn’t have to be super complicated, but just surprising.
…and then it turns out the explanation can be beautiful, and so elegant, and it makes sense in hindsight, at the time, it sounded ridiculous.” – Dr. Gregory Scholes
And then after that when you understand that it unfolds a whole new appreciation for how things work and what might be possible because of that knowledge.
And so we’ve definitely done experiments that were surprising or that I didn’t believe, and then it turns out the explanation can be beautiful, and so elegant, and it makes sense in hindsight, at the time, it sounded ridiculous.
Jed: Wow, that’s amazing. Well, I’m sure for the people who care most about your field, those particular stories would be truly inspiring to see after all those years, you finally got it to work, after all those years, you finally found an answer and it wasn’t the one you expected, but it makes it so elegant. So we’re just glad you’re working on these things, and we’re so thankful that you could take some time to explain a little bit of what you’re doing. Thank you for taking the time today, it was really nice to have you with us. Thank you.
Greg: Pleasure. Yeah, thanks Jed.