Category Archives: LED Packaging and Testing

“The sapphire industry is still plagued by overcapacity and rapid price declines,” asserts Yole Développement (Yole) in its latest report Sapphire Applications & Market 2016: LED & Consumer Electronics. Demand for LED is increasing but will not provide enough volumes to sustain the close to one hundred sapphire makers competing in the market. Yole estimates that up to 30 companies have stopped sapphire-related activities over the last 18 months. The most prominent were OCI, DK-Aztek, HQC, Shangcheng etc. Many more have frozen most of their capacity and China counts dozens of “zombie” companies only alive by political will.

sapphire market

This autumn is showing a new interest for sapphire and its numerous applications. Under this context, the “More than Moore” market research and strategy consulting company presents its latest report entitled Sapphire Applications & Market 2016: LED & Consumer Electronics report.
Moreover, in collaboration with CIOE, Yole also announces the Sapphire Forum, 2nd edition: 2nd International Forum on Sapphire Market & Technologies, taking place in Shenzhen, China, on Sept. 6 & 7. More information & Registration.

Is there still a future for sapphire display covers? How much can LED demand sustain the industry? Is China going to completely dominate this industry? Save the date and learn more about the sapphire industry with Yole’s analysts.

“Capacity increased again over the last 12 months, although the pace is abating, thanks to a reduction in the number of new projects and significant attrition,” explains Dr Eric Virey, Senior Market and Technology Analyst, LED & Sapphire at Yole. And he adds: “But continuous excess supply combined with the significant drop in LED wafer demand in Q3 and Q4-2015 led to an acceleration of ASP decrease over the last 12 months. Prices for cores and wafers have dropped 50 to 70% over the last 2 years. Four inch wafers have been hard hit and 2” cores now sell for no profits, as a fall-off of 4” and 6” manufacturing and for the sole purpose of absorbing fixed cost.”

The 2” core market is disappearing as the LED industry transitions to larger diameters and optical wafers are now a captive market. Suppliers need to find new applications for the parts of the boules that are left over after extracting 4” or 6” cores. For now, those are often sold by the kg at low prices for the manufacturing of small optical and mechanical parts.

With strong price pressure and an increasing fraction of the market being captive, revenue of sapphire companies have dropped 20% in 2015 despite a volume increase of 20% across all applications.

Unless strong signals emerge soon to indicate that the display cover opportunity could finally materialize in 2017, many more companies will disappear within the next 12-18 months. While this situation is critical for many players, on the longer term, the market will finally be weeded out of its weakest players. The survivors could emerge stronger and the overall industry healthier. “Despite a slight reshuffle in the ranking, the top 5 companies by revenue in 2015 remained the same as in 2014. But 2 newcomers from China, TDG and JeShine appeared in the top 20,” asserts Eric Virey from Yole.

On the way to industry maturity, new applications such as µLED displays could emerge. While they won’t represent an opportunity of the same scale as display covers, they could offer nice upsides to the companies that can capture them.

In Yole’s sapphire report, a detailed analysis of company revenues per region and product type as well as the update on capacity for crystal growth, finished and PSS wafers with all major changes and information on dozens of existing and emerging players have been detailed. More information is available on i-micronews.com, LED reports section.

Samsung Electronics Co., Ltd. today announced “H-series Gen 3,” a new line-up of LED linear modules that features high efficacy and enables easy replacement of fluorescent lights with LED lamps.

New Samsung LED H-series linear module for indoor lighting (Graphic: Business Wire)

New Samsung LED H-series linear module for indoor lighting (Graphic: Business Wire)

“With our new H-series, Samsung continues to lead the high-end industry segment for LED components through constant technology innovation,” said Jacob Tarn, executive vice president, LED Business Team, Samsung Electronics. “We are directing our technology expertise to improving the quality of LED lighting by significantly enhancing our LED components’ performance and overall competitiveness.”

Samsung’s H-series Gen 3 provides light efficacy reaching up to 187 lumen per watt (lm/W) at 4000K, which allows LED luminaires using the modules to achieve light efficacy above 140lm/W, delivering an optic efficiency level of about 86 percent and LED driver efficiency of approximately 88 percent.

Currently, Samsung offers several linear LED module line-ups: the V-series for cost-effective applications; the M-, S- and F-series for standard LED lighting segments; and now the H-series for high-performance LED products.

Samsung’s H-series Gen 3 uses the LM561C, the mid-power LED package with the highest efficacy in its LM561-series line-up. As a result, the H-series Gen 3 has obtained 18 to 26 percent higher efficacy than the company’s M-series Gen 2 modules. This feature makes the H-series Gen 3 line-up well-suited to meet DLC Premium standards – technical requirements for LED lighting solutions suggested by DesignLights Consortium™. DLC standards are well recognized in the North American region as a preferred means of evaluating LED lighting products in terms of performance and quality.

The H-series comes in three sizes: 1120mm (4 ft.) 560mm (2 ft.) and 280mm/275mm (1 ft.). As the premium version of the company’s M-series and S-series line-ups, the H-series has the same form factors as those modules (see chart below), while providing a performance level that more than satisfies the high demands of the U.S. and EU luminaire markets.

Samsung’s M-series has been certified by UL, a product quality certification standards organization in the U.S., while the S-series has been certified by CE and ENEC, similar standards bodies in the EU. Sharing the form factors and quality certifications of Samsung’s M- and S-series, the H-series allows lighting manufacturers to select their LED modules according to the specific operating conditions of their applications.

In a short term, UV curing will drive the UV LED market, announces Yole Développement (Yole) in its new LED report entitled UV LEDs: Technology, Manufacturing and Applications Trends.

But UVC LED’s recent price reduction will see the UV disinfection/purification market take over the UV curing market by 2019/2020. In this context, Yole’s analysts expect the UVC LED market to strongly grow from US$7 million in 2015 to US$610 million by 2021.

uv led curing

With an increased penetration rate in all applications, the UVA LED market will grow from US$107 million in 2015 to US$357 million by 2021. In addition to a moderated growth due to price pressure, Yole announces a very strong increase in number of devices.

Under this new UV LED report, 2016 edition, Yole details the latest technology and market trends. This comprehensive survey provides a deep understanding of the UV lamp business and its technological transition to UV LEDs. It is a thorough analysis of each UV lamp application (UVA/UVB/UVC) with a specific focus on UV curing, UV disinfection/purification and analytical instruments using UV light. Yole’s report highlights the global UV LED industry trends, from substrate to system and details the main challenges and axis of research.

“The UVC LED industry is still small but strong growth is expected in the next 18 months due to dramatic price reductions”, explains Pierrick Boulay, Market & Technology Analyst, LED & OLED at Yole. And he adds: “In 2016 prices are 1/8-1/10 of what they were in 2015.”
This has been triggered by the industry’s development, its transition to mass production and improved device performance. With most of the industry believing that US$1-US$4/mW is the price that would trigger mass market adoption we are getting close to a UVC LED market boom. Another positive sign is that most UVC LED manufacturers are now focusing on developing cost-effective solutions rather than improving device power output. In parallel, the UVC LED industry continues to work on increasing lifetime and developing lower wavelength devices, below 280nm.

In parallel, UVA LEDs continue to progress in the UV curing space. “Continuous improvement of device performance coupled with price reduction has allowed the technology to be increasingly adopted in UV curing applications”, asserts Pars Mukish, Business Unit Manager, at Yole. “Penetration of UV LEDs is increasing but we observe differences in adoption rates depending on application.” Small size and low speed applications like spot adhesive and digital inkjets have the highest adoption rate, and most new developments use UV LEDs. This is due to the small module size and low irradiance level needed that limits the extra cost of integrating UV LEDs compared to the total price of systems like inkjet printers. On the other hand, applications that need high speed processes and/or high levels of irradiance such as screen printing or coating applications have lower adoption rates. This is because UV LED performance is not yet good enough to fully replace traditional mercury lamps.

“Today UVA still represents the largest UV LED market but this trend could change in the future as UV LED performances increase,” announces Yole’ analysts. UV LEDs also enable new applications inaccessible to UV lamp. If these new applications take off, they could represent and additional revenue of nearly US$143 million in 2021.

Yole’s UV LED report highlights the market structure, UV LED market drivers and associated technical challenges, recent trends and new applications created by UV LEDs. It also includes UV LED market size split by application, and much more.

IHS Markit (Nasdaq: INFO) today released its annual 2015 revenue-share ranking of the top LED suppliers in backlighting, automotive, lighting and other applications.

According to the 2016 edition of the IHS Markit Packaged LED Report, Nichia led in both lighting and mobile applications for 2015, with 12.9 percent share of the total packaged LED market. Nichia was followed by Osram and Lumileds with a combined share of 14.7 percent.

“It’s not a surprise that Nichia led in more than one application,” said Alice Tao, senior analyst, LEDs and lighting for IHS Markit. “In 2015, Nichia overtook Cree, which led the lighting category in 2014. Nichia was also very strong in mobile phone LEDs, since the company is a major supplier for Apple’s iPhone.”

Samsung was the leading supplier in backlighting, which includes LEDs used in TVs, monitors, notebook PCs and tablet PCs. Nichia followed in second position and LG Innotek ranked third.

Osram has been the leading supplier of automotive LEDs for many years. Its market share was 35 percent in 2015 for LEDs used in the total automotive market and 40 percent for those used in the automotive exterior market. It also led in the “other” application, which includes LEDs used for industrial, medical, security, projection, signage and off-specification applications.

Leading packaged LEDs suppliers
(Millions of Dollars)  
   
Category

Leading supplier
Lighting

Nichia
Backlighting

Samsung
Mobile phone

Nichia
Automotive

Osram
Other

Osram

 

The IHS Markit Packaged LED Report provides detailed quantitative market sizes and supplier shares by application, region and product type. For more information about purchasing IHS Markit information, contact the sales department at [email protected].

Pixelligent Technologies, a developer of high-index advanced materials for solid state lighting and display applications and producer of PixClear products, announced today that it closed $10.4 million in new funding. The round was led by The Abell Foundation, The Bunting Family Office, and David Testa, the former Chief Investment Officer of T. Rowe Price. Funds will be used to complete the installation of additional manufacturing capacity, open new offices in Asia, and continue to drive innovation in lighting, display and optical applications.

To date Pixelligent has raised over $36.0M in equity funding and has been awarded more than $12M in U.S. government grant programs to support the development of its proprietary PixClear products and PixClearProcess. The Pixelligent nanotechnology platform includes proprietary nanocrystal synthesis, capping technology, high volume manufacturing and application engineering that supports ink jet, slot die, UV curing, spray coating, and numerous other manufacturing processes.

“We have clearly established Pixelligent as the leading high-index materials manufacturer for demanding solid state lighting and OLED display applications throughout the world. Pixelligent is partnering with leading advanced materials suppliers to deliver breakthrough performance that currently spans applications in 12 discrete markets including: lighting, displays, printed and flexible electronics, AR/VR, optically clear adhesives, MEMS, gradient index lenses, and others with a combined total over $9B in market opportunities. We have numerous commercial applications currently in the market and expect additional product introductions before the end of 2016,” said Craig Bandes, President & CEO of Pixelligent Technologies.

“We started our partnership with Pixelligent in 2011 when the company relocated to Baltimore City and have seen the company achieve all of their critical technology and manufacturing milestones, while establishing a global brand and presence. Our investment objective is to support leading edge companies that deliver breakthrough technology and products and create jobs in our local community. Pixelligent is at the forefront in delivering on the promise of the nanotechnology revolution. We are proud of what the team at Pixelligent has accomplished to date and we look forward to their continued growth and success,” said Eileen O’Rourke, CFO of The Abell Foundation.

Veeco Instruments Inc. (NASDAQ: VECO) announced today that Epistar Corporation (TSE: 2448) has ordered multiple TurboDisc EPIK 700 Gallium Nitride (GaN) Metal Organic Chemical Vapor Deposition (MOCVD) Systems for the production of light emitting diodes (LEDs). The Veeco systems will be used to meet demand for various applications.

“The improved demand of solid state lighting combined with the need to compete in a competitive market dictates we choose the most productive and most cost-efficient MOCVD platform in the industry,” said Dr. MJ Jou, President, Epistar Corporation. “Veeco has been our supplier of choice dating back to their innovative K465i system. After adopting their latest EPIK platform, we have achieved superior yield results and lowered manufacturing costs. The addition of these new EPIK MOCVD systems will help advance our production goals and improve our product competitiveness.”

Based on Veeco’s proven TurboDisc technology and the proprietary Uniform FlowFlange, the award-winning EPIK 700 MOCVD system enables customers to achieve an improved cost per wafer savings compared to previous MOCVD systems through improved wafer uniformity, reduced operating expenses and increased productivity.

“We believe that a leader such as Epistar ramping production to meet demand of LEDs is a positive sign for the industry as a whole,” said James T. Jenson, Senior Vice President, Veeco MOCVD Operations. “Veeco’s superior MOCVD technology is the number one choice of manufacturers looking for a competitive edge in a market that seems to be turning upward again. We look forward to supporting Epistar’s future MOCVD requirements as they continue their growth plans.”

The upconversion of photons allows for a more efficient use of light: Two photons are converted into a single photon having higher energy. Researchers at KIT now showed for the first time that the inner interfaces between surface-mounted metal-organic frameworks (SURMOFs) are suited perfectly for this purpose – they turned green light blue. The result, which is now being published in the Advanced Materialsjournal, opens up new opportunities for optoelectronic applications such as solar cells or LEDs. (DOI: 10.1002/adma.201601718)

Photon upconversion: energy transfer between the molecules is based on electron exchange (Dexter electron transfer). Credit: Illustration: Michael Oldenburg

Photon upconversion: energy transfer between the molecules is based on electron exchange (Dexter electron transfer). Credit: Illustration: Michael Oldenburg

Metal-organic frameworks (MOFs) are highly ordered molecular systems that consist of metallic clusters and organic ligands. At the Institute of Functional Interfaces (IFG) of KIT, researchers developed MOFs that grow epitaxially on the surfaces of substrates. These SURMOFs (surface-mounted metal-organic frameworks) can be produced from various materials and be customized using different pore sizes and chemical functionalities so that they are suited for a broad range of applications, e.g. for sensors, catalysts, diaphragms, in medical device technology or as intelligent storage elements.

Another field of application is optoelectronics, i.e. components that are capable of converting light into electrical energy or vice versa. Many of these components work on the basis of semiconductors. “The SURMOFs combine the advantages of organic and anorganic semiconductors,” Professor Christof Wöll, Director of IFG, explains. “They feature chemical diversity and crystallinity, allowing us to create ordered heterostructures.” In many optoelectronic components, a so-called heterojunction – this is an interfacing layer between two different semiconductor materials – controls the energy transfer between the various excited states. Researches of the KIT Institute of Microstructure Technology (IMT) now created a new piggyback SURMOF in which a second SURMOF grew epitaxially, i.e. layer by layer, on a first one. At this heterojunction, it was possible to achieve photon upconversion, transforming two low-energy photons into a single photon with higher energy, by virtually fusing them together. “This process turns green light blue. Blue light has a shorter wavelength and yields more energy. This is very important for photovoltaics applications,” explains Professor Bryce Richards, Director of IMT. The scientists are presenting their work in Advanced Materials, one of the leading journals for materials science.

The photon upconversion process shown by the Karlsruhe researchers is based on the so-called triplet-triplet annihilation. Two molecules are involved: a sensitizer molecule that absorbs photons and creates triplet excited states, and an emitter molecule that takes over the triplet excited states and, by using triplet-triplet annihilation, sends out a photon that yields a higher energy than the photons that were originally absorbed. “The challenge was to create this process as efficiently as possible,” explains Dr. Ian Howard, leader of a junior research group at IMT. “We matched the sensitizer and emitter layers in a way to obtain a low conversion threshold and a higher light efficiency at the same time.”

Since the triplet transfer is based on the exchange of electrons, the photon upconversion process revealed by the researchers includes an electron transfer across the interface between the two SURMOFs. This suggests the assumption that SURMOF-SURMOF heterojunctions are suitable for many optoelectronic applications such as LEDs and solar cells. One of the limitations for the efficiency of today’s solar cells is due to the fact that they can only use photons with a certain minimum energy for electric power generation. By using upconversion, photovoltaic systems could become much more efficient.

Researchers at the University of Illinois at Urbana Champaign have developed a new method for making brighter and more efficient green light-emitting diodes (LEDs). Using an industry-standard semiconductor growth technique, they have created gallium nitride (GaN) cubic crystals grown on a silicon substrate that are capable of producing powerful green light for advanced solid-state lighting.

A new method of cubic phase synthesis: Hexagonal-to-cubic phase transformation. The scale bars represent 100 nm in all images. (a) Cross sectional and (b) Top-view SEM images of cubic GaN grown on U-grooved Si(100). (c) Cross sectional and (d) Top-view EBSD images of cubic GaN grown on U-grooved Si(100), showing cubic GaN in blue, and hexagonal GaN in red. Credit: University of Illinois

A new method of cubic phase synthesis: Hexagonal-to-cubic phase transformation. The scale bars represent 100 nm in all images. (a) Cross sectional and (b) Top-view SEM images of cubic GaN grown on U-grooved Si(100). (c) Cross sectional and (d) Top-view EBSD images of cubic GaN grown on U-grooved Si(100), showing cubic GaN in blue, and hexagonal GaN in red. Credit: University of Illinois

“This work is very revolutionary as it paves the way for novel green wavelength emitters that can target advanced solid-state lighting on a scalable CMOS-silicon platform by exploiting the new material, cubic gallium nitride,” said Can Bayram, an assistant professor of electrical and computer engineering at Illinois who first began investigating this material while at IBM T.J. Watson Research Center several years ago.

“The union of solid-state lighting with sensing (e.g. detection) and networking (e.g. communication) to enable smart (i.e. responsive and adaptive) visible lighting, is further poised to revolutionize how we utilize light. And CMOS-compatible LEDs can facilitate fast, efficient, low-power, and multi-functional technology solutions with less of a footprint and at an ever more affordable device price point for these applications.”

Typically, GaN forms in one of two crystal structures: hexagonal or cubic. Hexagonal GaN is thermodynamically stable and is by far the more conventional form of the semiconductor. However, hexagonal GaN is prone to a phenomenon known as polarization, where an internal electric field separates the negatively charged electrons and positively charged holes, preventing them from combining, which, in turn, diminishes the light output efficiency.

Until now, the only way researchers were able to make cubic GaN was to use molecular beam epitaxy, a very expensive and slow crystal growth method when compared to the widely used metal-organic chemical vapor deposition (MOCVD) method that Bayram used.

Bayram and his graduate student Richard Liu made the cubic GaN by using lithography and isotropic etching to create a U-shaped groove on Si (100). This non-conducting layer essentially served as a boundary that shapes the hexagonal material into cubic form.

“Our cubic GaN does not have an internal electric field that separates the charge carriers–the holes and electrons,” explained Liu. “So, they can overlap and when that happens, the electrons and holes combine faster to produce light.”

Ultimately, Bayram and Liu believe their cubic GaN method may lead to LEDs free from the “droop” phenomenon that has plagued the LED industry for years. For green, blue, or ultra-violet LEDs, their light-emission efficiency declines as more current is injected, which is characterized as “droop.”

“Our work suggests polarization plays an important role in the droop, pushing the electrons and holes away from each other, particularly under low-injection current densities,” said Liu, who was the first author of the paper, “”Maximizing Cubic Phase Gallium Nitride Surface Coverage on Nano-patterned Silicon (100)”, appearing Applied Physics Letters.

Having better performing green LEDs will open up new avenues for LEDs in general solid-state lighting. For example, these LEDs will provide energy savings by generating white light through a color mixing approach. Other advanced applications include ultra-parallel LED connectivity through phosphor-free green LEDs, underwater communications, and biotechnology such as optogenetics and migraine treatment.

Enhanced green LEDs aren’t the only application for Bayram’s cubic GaN, which could someday replace silicon to make power electronic devices found in laptop power adapters and electronic substations, and it could replace mercury lamps to make ultra-violet LEDs that disinfect water.

The gallium nitride (GaN) substrates market is set to cross $4 billion USD by 2020, according to the market research report “Gallium Nitride (GaN) Substrates Market Analysis: By Type (GaN on sapphire, GaN on Si, GaN on SiC, GaN on GaN); By Products (Blu-ray Disc (BD), LEDs, UV LEDs) By Industry (Consumer Electronics, Telecom, Industrial, Power, Solar, Wind)-Forecast(2015-2020)”, published by IndustryARC.

Gallium Nitride (GaN) is a semiconductor compound material which has proved to be advantageous in comparison to the other conventional materials such as Silicon, Silicon Carbide, Aluminum, and so on. GaN substrates are essential materials which are deployed across blue-violet laser diodes in recorders or BD players and the power control elements. GaN materials are also used across optoelectronic products such as lasers, LEDs, Power Electronics and Radio Frequency amplifiers.

Optoelectronics are the key devices that employ GaN substrates, among which, LEDs account for over 70% share. Traditionally, these devices are grown on GaN on Sapphire, GaN on Si, and GaN on Sic substrates with GaN on Sapphire being the most utilized substrate. However, these substrates contain GaN layers grown by epitaxial methods leading to lattice mismatches and defects. In this context, the gallium nitride substrates are presented as the potential substitute for the foreign substrates. The GaN epitaxy if performed on the native substrates has several technical advantages and also improves the performance of the devices.

According to recent study by IndustryARC, the GaN substrates market is dominated by sapphire which is nearing maturity. The market for sapphire substrates was around $ 1.4 billion in 2014 and estimated to grow at 7% CAGR in 2015-2020. The market is estimated to showcase normal growth rates and grow predictably till 2020 and if any disrupting market developments are expected from the silicon and bulk GaN substrate areas. There is only company, Cree Inc. manufacturing GaN on SiC products and very few players adopting GaN on Si. Acquisitions and partnerships are going to be the key in these segments to showcase significant growth in the next five years.

Asia-Pacific is the key region for both substrates and devices market. LEDs, with demand in particular from automotive and lighting industry, are estimated to drive the GaN market in the period 2015-2020. In this, region, Japan, China, and Korea are the key regions where majority of the players are located and demand emerges. The less labor and production costs in these countries are aiding manufacturers to set up production facilities. In 2015, Panasonic Corporation has shifted its LED production to Japan from Indonesia to capitalize these advantages in the country and further grow its share in the LED market. Besides that, the substrate suppliers are also strongly distributed in the region. With these players significantly scaling up their global market position, the prices are estimated to be affected significantly. In countries such as China, the substrates are offered at cheaper prices which will not only attract LED producers significantly but also intensify demand for cheaper products.

The bulk GaN or GaN on GaN substrates hold lot of promise in the LED, Power Electronics, and RF products. Particularly in power electronics, the bulk gallium nitride substrates are proven to be very useful. There is significant research underway to realize the GaN material potential into these industries and very recently, MIT researchers have successfully enabled GaN power transistors at low cost. Due to huge power saving nature of the components made from them, the billion dollar markets such as internet of things and electric vehicles market are only ready to embrace bulk GaN substrates. Thus, with encouraging developments in the market and potential billion markets, bulk GaN is projected as the game changer. But, to realize the same, there are substantial obstacles in terms of production and capital. Therefore, even in 2020, the market is estimated to be dominated by foreign substrates where bulk GaN will account for smaller share.

A collaboration of researchers from Kumamoto, Yamaguchi, and Osaka Universities in Japan have discovered a new method of drastically changing the color and fluorescence of a particular compound using only oxygen (O2) and hydrogen (H2) gases. The fully reversible reaction is environmentally friendly since it produces only water as a byproduct. Rather than using electrical or photo energy, the discovery uses energy from the gases themselves, which is expected to become a future trend, to switch the color and fluorescence properties. The technique could be used as a detection sensor for hydrogen or oxygen gases as well as for property controls of organic semiconductors and organic light emitting diodes (OLEDs).

An efficient chemical synthesis method for picene-13, 14-dione. Credit: Dr. Hayato Ishikawa

An efficient chemical synthesis method for picene-13, 14-dione. Credit: Dr. Hayato Ishikawa

Polyaromatic compounds (PACs) are widely used in fluorescent materials, semiconductor materials, organic EL devices, and organic solar-cell devices. The research performed at Kumamoto University focused on using energy from gases to trigger a molecular switch in a PAC. In particular, focus was placed on H2 as a reductant and O2 as an oxidant.

“We tried to determine the most attractive compounds that could freely and dramatically change the optical properties of the PAC with a redox reaction,” said Associate Professor Hayato Ishikawa from Kumamoto University. “Specifically, we introduced an orthoquinone moiety to the PAC that possessed the most ideal switching properties under a redox reaction with hydrogen and oxygen gases.”

To determine the candidates with the best switching properties, researchers screened several orthoquinone-containing aromatic compounds in a computational study. The ideal molecules clearly showed switching between fluorescence emission and quenching, and between a colored and colorless state.

Picene-13, 14-dione was nominated as the most promising candidate from the computational analysis. The researchers then developed an original protocol to efficiently synthesize the compound from commercially available petroleum raw materials. The key steps for the synthesis were the transition metal-catalyzed coupling reaction and the ring construction reaction by an organocatalyst. This synthetic methodology is also applicable to the synthesis of various other similar compounds or derivatives.

A palladium nanoparticle catalyst was added to the synthesized picene-13, 14-dione and then H2 gas was bubbled into the solution. As predicted by the computational study, a dramatic change in color and fluorescence of the solution was observed; its color and fluorescence changed from yellow to colorless, and from non-fluorescent to blue fluorescent respectively. The subsequent reverse oxidation proceeded smoothly when H2 gas was exchanged for O2 gas, and the solution reverted back to its original state.

“When we performed a detailed analysis, it was revealed that the resultant changes in color and fluorescence were caused by two different molecular states. The prediction of these states, and our ideas about this phenomenon, were strongly supported by both the computational analysis and the experimental results,” said Associate Professor Ishikawa. “This molecular switching technology of an aromatic compound using an orthoquinone moiety is a new insight that appears to have been reported first by our research team.”

An important advantage of this technology is that it is environmentally friendly since the byproduct of the reaction is simply water. Additionally, the synthetic PACs don’t experience very much damage after each reaction meaning that the molecular switch has excellent reusability.

“We have considered a wide range of future applications for this molecular technique,” said Associate Professor Masaki Matsuda, a research collaborator from Kumamoto University. “For example, we can put this molecular sheet into a package of food filled with an inert gas to check whether oxygen, which promotes the spoilage of food, has entered the package. All that would be required is a simple check under a UV light; the package wouldn’t even have to be opened. Organic semiconductors and OLEDs could also benefit from the ability to control optical properties using energy from gases. For example, organic semiconductors could be made to change their electrical properties, and OLEDs could show on/off switching characteristics by using the energy from gas that is supplied to it. The applications for this technology are numerous.”

The findings of this research were published in the Angewandte Chemie International Edition, online edition, on May 4th, 2016.