The Germ Killers: LED Lights with UV-C Radiation

The OSRAM Podcast: Episode #2 with Hans Lugauer

Welcome to The Photonstudio, an OSRAM Podcast. My name is Karin Steinmetzer and I am an OSRAM employee in the Communications department. In this episode of our podcast, I want to find out what light can do to combat viruses, which is currently a hot topic. Because of the corona virus we are all currently experiencing very specifically where viruses are present wherever we do not want them and what they can do in extreme cases.

In this episode of our podcast we therefore ask what role a certain spectral range of light, namely ultraviolet radiation, can play in the fight against germs. This is why I am talking to OSRAM development engineer Hans Lugauer today. He is working with colleagues from the Opto Semiconductors business unit in Regensburg on the development of germicides using UV-C radiation. I am looking forward to hearing from him where research is currently at, which products are already in use and what we can look forward to in the future.

Karin: Hello Hans, from home office to home office. Which product would you like to have in your hands today?

Hans: Hello Karin, we are currently working quite intensively on LEDs, i.e. light emitting diodes that can emit UVC light. Among other things, the light has the property of killing almost all kinds of germs, i.e. bacteria, viruses, molds and all other dangerous micro-organisms. In the midst of the corona crisis, it would be great if we had these LEDs available as a product in the market. But without a time machine, it will probably take us just under a year to develop this.

Karin: It's been a while since physics class. Could you briefly explain to us what wavelength exactly is the UVC radiation?

Hans: Well, UV light is usually divided into three groups: UVA, UVB and UVC. UVA is actually known from the tanning salon or from the sun. This is the proportion of light between 320 and 400 nanometres that is responsible for the tanning of the skin. UVB is then the range below 280 to 320 nanometres. That means a little tanning, but also a lot of sunburn. So this is all the spectral range from the sun that really causes sunburn and is therefore rather dangerous. UVC light is even lower, at 280 to 200 nanometres. That doesn't actually get to the surface of the Earth because it’s filtered out by our atmosphere. But that is actually very, very efficient in killing germs. It has just this special property. This special property is already present in traditional UVC lamps, the so-called low-pressure discharge lamps. These have been used in China during the Corona pandemic.

Karin: Could you perhaps explain to us in a little more detail why they are not used on a large scale?

Hans: This UVC radiation from mercury discharge lamps has been around for many decades. OSRAM also manufactures these lamps and has a disinfection product in its portfolio in the form of the AirZing lamp. It was tested in numerous hospitals and kindergartens (e.g. in Wuhan and Beijing) during the corona crisis in China. A great advantage of this UVC disinfection system is that it works without chemicals and is therefore of course ideal for such an environment where contamination is to be avoided.

Karin: So what can an LED do better now?

Hans: This brings us to the disadvantages that these lights have. As the name mercury discharge lamp suggests, they contain mercury. This means that they are not entirely harmless to health, especially if they are damaged or if they are not disposed of properly. This means that mercury can then escape into the environment. Other disadvantages would be that they are also quite large and that it is difficult to reduce them in size. They are particularly sensitive to mechanical shocks and impacts. Even if you switch them on and off frequently, they break down quickly. Another disadvantage is that, depending on the application, they usually need a few minutes after switching them on before they even burn at full power. So turning them on and off quickly does not really work. Beside the lifetime, also the light output is very slow until it burns to full power. That's when the advantages of LEDs really become apparent. Of course, they do not contain any heavy metals from the process. They are very, very small, so they can be used flexibly in all kinds of product geometries. You can switch them on and off as often as you like, they don't mind at all. Also, the light is fully present immediately after switching on and there is no delay at all. Furthermore, you do not need such high voltages as the discharge lamps. This means that you could also operate them with batteries or rechargeable batteries and thus in principle take them everywhere.

Karin: These are very clear advantages, which then also enable completely new fields of application. But we don't have the UVC LED in our hands yet, so what exactly is the challenge in development?

Hans: This LED technology has been around since the 1960s. A great deal has happened in the last 20 years since the blue LED began its triumphant advance. As you have already said, it can be found in almost every house in the form of white LEDs, where the blue light is supplemented by yellow to white. But the technology behind these blue LEDs is quite similar to that of UVC LEDs. If you take a closer look at the material, they are semiconductors. And the blue LEDs are made of the semiconductor indium gallium nitride, while the UVC LEDs are made of aluminum gallium nitride. This means that you can set the wavelength you want by the amount of indium or aluminum. That sounds simple, so we exchange the indium for the aluminum. But exactly this is quite challenging in the implementation.

Karin: Could you perhaps explain it to us a little more precisely? First of all it actually sounds quite simple to exchange one material for another. But what does it all involve?

Hans: Exactly that sounds simple. But that's the real challenge when you put it into practice. For example, if you now start with the semiconductor aluminum nitrite, which forms the basis of UVC LEDs, you need very, very high temperatures in the production process in order to achieve optimal results. Now, even with normal gallium nitride LEDs for the visible range, it is already a very demanding process that runs at over a thousand degrees Celsius. And for the aluminum nitrite, you have to add another 300 to 400 degrees. The existing process systems cannot cope with this. New equipment is needed for this and new processes have to be developed accordingly, which ultimately deliver the necessary quality and yield.

Karin: That means it takes time. What is the time horizon we are talking about in terms of development?

Hans: As mentioned, these new materials are relatively complex to manufacture. There are many problems and challenges to be solved. This will certainly not happen overnight. Here we are already talking about a time scale of about one year. We are still in the pre-development phase at the moment. This means that we still have to develop all these processes and introduce them in a production-ready form. Normally, it would probably take another year or so. But, of course, we are really stepping on the gas in the current situation.

Karin: I can see that we still need a little patience until we have the UVC LED in our hands. Now I'm interested in something else. How does the destruction of germs by UVC radiation actually work? Where and how do they attack exactly?

Hans: Destruction is perhaps not quite the right word. After all, we don't explode the germs or vaporize them with the light beam, as you might imagine. I think deactivating or preventing them from multiplying is perhaps a better term. A single bacterium or virus isn't so bad in itself. It only becomes dangerous if it can multiply in large numbers and can flood the body's defense system accordingly. Normally, the body's defenses keep a certain number of germs in check. But if there are too many, then we have no chance at all and the person becomes ill. So the real problem is reproduction. At each reproduction step, a copy of the genetic material must be produced so that the next generation of the germ has the same characteristics as the previous one. And this is where the UVC light comes in. It is possible to damage this genetic material by irradiating these high-energy UV photons, i.e. in the range 270 to 260 nanometres, in such a way that it can no longer be copied properly. The copy is then immediately destroyed or is not even generated in the first place. In other words, this reproduction of the germ is thus stopped and the germ has become inactive.

Karin: Understood. Now there are germs not only in Corona times, can you describe us some applications for which the UVC germicides can be used afterwards? What kind of UVC LED products do you have in mind?

Hans: Of course there are some in the field of water. For example, you can imagine that you can use the components in washing machines or dishwashers to prevent germs and odors. As is well known, air conditioners are also quite germ-spinning in the air if they are not carefully maintained, for example. Here, too, UVC LEDs can be used at the right place in the air conditioning system to prevent germs and the corresponding danger to users. If you now turn your attention back to the surfaces, you won't be able to avoid the corona crisis altogether, because that was the main topic. But in general, there are also multi-resistant germs in hospitals, for example, against which no medication is really effective. At the moment, these germs have to be addressed with hard chemistry, but it is not quite possible to do so. In public areas such as buses and trains, taxis, rental cars or escalators, i.e. anywhere where many people touch the same things one after the other, the use of UVC light is certainly very useful. You just have to make sure that the radiation is sufficiently shielded and that no one is around when it is on. But I think it is clear that this is done in each application.

Karin: Now we've talked about applications, material systems and wavelengths, but not yet about the efficiency of UVC LEDs, which is a very important factor for their economical use. When will we be able to use UVC LEDs where we have been with everyday LEDs for a long time?

Hans: It is indeed one of the biggest challenges with the material to get out the UVC photons that are generated inside these semiconductors. This sounds simple at first but is actually terribly difficult in detail because this light extraction is particularly bad there due to material properties. We are talking about light extraction efficiency of less than 10 percent. In other words, compared to the blue LEDs, we are missing at least a factor of five or even significantly more, depending on what you compare it to.

Karin: Does that mean that this is now roughly where we were ten years ago with everyday LEDs?

Hans: Yes, exactly.

Karin: But you don't need ten years to catch up now?

Hans: No, of course not. Fortunately, we already know a large arsenal of concepts from the learning phase of visible LEDs, which we already have available to tackle this very problem. For example, you can roughen surfaces, there are various tricks for this. You can try to make the absorbing layers, which may still be inside, as thin as possible or get them out completely. We already know a few things that helped with the visible LEDs and of course we still have to try for the UVC LEDs, but all of them are quite promising and certainly won't take as long as it took to develop it for the first time.

Karin: That means that the UVC LED is coming within reach. Then I would like to come back to the advantages again. The LED is much smaller and can be installed directly where it is needed. For example, directly into the water tap. He can't do that with current solutions, right?

Hans: That's right! It doesn't work directly at the tap, firstly because of the size, that would simply be an unshaped part, and secondly because of the high voltage that would be needed directly around the water. One would not do that, simply for safety reasons. So it is a classic advantage for the LEDs.

Karin: And what about surface disinfection, for example? Could I imagine a portable disinfection device on LED basis as a product? Such a germicide To-Go, with which I can disinfect things that I would rather not touch at all?

Hans: Exactly, you can imagine that too. It is absolutely possible to produce a portable device with LEDs and battery operation. You just have to make sure that you observe certain safety regulations, because the UVC radiation itself is of course not completely harmless, even for humans. This means that it must be ensured that the device switches itself off when the person is in the immediate vicinity or looks in. Of course, this should not happen, but in principle it is of course a very interesting application, if I myself can contribute to it. Wherever I feel uncomfortable, I can use it and clean objects or surfaces accordingly.

Karin: That means that there must be a sensor system in the product that ensures that nobody is harmed by the UVC radiation?

Hans: For example, you can try to detect the direction of the device in the room in such a way that it only works when it is directed downwards, so that it never works if you hold it at an angle and the person would get a part of the radiation. That would be a relatively simple possibility for example. With portable devices it is of course rather difficult. With fixed devices it would require a motion detector nearby.

Karin: Such a product would really make life a lot easier, especially at the moment! But now back to you personally. You've been working in UVC research for a long time and it's a job with many unknowns along the way. How do you handle it?

Hans: This is a real challenge. But not only for me, but for everyone involved, because we're dealing with a new material and therefore a new component that can really surprise us. This means that, in addition to really detailed and detailed project planning, a pragmatic approach to problems will also be required later on, because you can only foresee these to a limited extent during planning. And when problems arise, they have to be solved or avoided. But that takes up a large part of the developer's everyday life. That's exactly where the appeal of the job lies for me, because I personally get the greatest motivation from the moments when a new idea appears or a new insight is found that solves the very problem that was causing you headaches for days or even weeks before. And then it goes on, solving the next problem and carrying out this loop until the end.

Karin: Sounds like great stamina. Specifically, about your tasks, which one do you enjoy the most?

Hans: The daily work of a developer has a lot to do with bureaucracy, but fortunately, for the most part, also a lot to do with problem solving. This is what I personally enjoy most when I have a problem - I need to take a closer look and understand where it comes from. And when at some point I have found the solution and in the end, I have a product in my hands, such as the UVC LED, it really adds value. And that as OSRAM you can make a contribution to making the world a little bit better, that is also great.

Karin: Describe for us in more detail how you get there. What does your everyday working life look like? Are you in the laboratory or do you analyze spectral curves on the computer? Or do you work on material systems? How exactly can we imagine that?

Hans: It depends on the special work packages you are working on. A lot of things are solved or viewed in the lab, of course. In detail, however, one usually comes together with other developers and discusses results, measures values and then actually tries to draw a conclusion from these results, derive how to do something better, and how to do something differently so that this problem does not occur in the way it might at the moment. That means you have to be flexible and creative. That is really very, very important in this job. Without such creative ideas it becomes very, very difficult to solve these problems.

Karin: I would not have assigned creativity to a physicist in the first place. I have a bit of a nerd in mind. What exactly is creative about your work?

Hans: So first of all, thank you for the nice compliment. Creativity as a physicist is actually a basic requirement. I don't think you can get very far without it. We have questions that arise in many places, which we have to solve with appropriate ideas, i.e. a lot of creativity. That sounds abstract now, but I can try to give you a few examples. In principle, our process chain can be divided into two main groups. One is epitaxy, i.e. the deposition of the semiconductor layers, which also generate the light at the end. The second is chip processing, which uses the wafer coming from epitaxy to later structure the small chips. This means that a large wafer is made into very, very small chips. And these two processes are of course closely related. It's a big challenge when a problem comes up at the back. For example, if the operating voltage of the component is much too high, you don't know if it's because of the epitaxy or the chip process. This is the challenge of narrowing down the error with many individual experiments. Where exactly does it come from and how can it be solved if you have a rough idea where it really comes from. That's the real challenge and, as I said, that's the fun you have when you finally solve a bigger problem.

Karin: So you probably need a high frustration tolerance?

Hans: Indeed, the frustration tolerance increases with the complexity of the issues. With this topic, precisely because it is so new, there are a lot of questions and unknowns that really hit home. And accordingly, there are many moments when people say that there is no such thing, how does something like this come about? And that's where you have to delve into and go into detail and try to identify the reasons and causes. That is sometimes very time-consuming and doesn't happen as quickly as you would like, and you need a lot of patience. Those are the real challenges of the everyday life of a developer.

Karin: Problem solving is good, but you don't have to solve all problems yourself and you don't have to have all ideas yourself. We are certainly not the only ones researching UVC LEDs. Do you work together with partners to make things happen faster?

Hans: Of course, many questions cannot be answered completely in one company. There are many problems where a university is better placed to address such things. We have well-functioning cooperations, for example with the TU Braunschweig, which then takes a closer look at specific questions for us and then investigates them in great detail with their analytics tools, and which can then find other questions and also other solutions than we can, due to the possibilities they have.

Karin: What can we look forward to next year?

Hans: I hope first of all that we all get rid of the corona virus topic from our everyday life and that it is no longer as dominant as it is right now. I think we are all looking forward to that. Then, of course, I hope that this planned product development project really does go exactly as planned. That is always the big question, but if it does, we will really be able to have the first productive OSRAM UVC LEDs in 2021. After the eternal time in pre-development, with many one-way streets and setbacks, I am particularly looking forward to when that time comes. Of course, I also hope that we can all be happy about such a component. Ultimately, it has the potential to make our everyday lives much safer, at least in terms of physical health. I think that's something very special about this technology.

Karin: Thanks, Hans, for the really exciting insight into your work!

Hans: Yes of course Karin, you're welcome! I would also like to thank you for the opportunity to contribute to this interesting topic.

You can listen to the current episode of our Photonstudio in German on Soundcloud, iTunes, Spotify and Google Podcast. If you want to know more about the germicides, I recommend the online version of our Innovation magazine ON. On the OSRAM Group website in the Innovation section you will also find many other inspiring articles from the world of photonics. Stay healthy and stay in the photon studio until the next episode. Bye!

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