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EETE OCT 2013

True white LEDs on the horizon By R. Colin Johnson Today , white LEDs are not really white, but instead use techniques such as combining the light emission of separate red, blue, and green (R-G-B) LEDs, or coat blue LEDs with yellowish phosphors. Now, researchers at the University of Utah have found a way to tune the color of emission of a polymer semiconductor in hopes of creating organic light emitting diodes (OLEDs), which produce true white light. The technique inserts platinum atoms inside the polymer interchain of an organic semiconductor, with different spacings allowing it to produce different colors of light. Their hope is to create a polymer with various spacings of platinum atoms, allowing them together to create white light from a single material. “We put the platinum atoms inside a polymer interchain using a synthetic process,” said University of Utah Professor Z. Valy Vardeny in a telephone interview with EE Times. “And we change the spacing between the platinum Z. Valy Vardeny, University of Utah physicist, uses a glove box to handle light-emitting polymers under cleanroom conditions. Source: University of Utah atoms to tune the color emitted.” In addition, the platinum-rich polymers not only fluoresce, like R-G-B LEDs, but also phosphoresce like phosphor-coated LEDs, potentially making them much more energy efficient than traditional OLEDs. “OLEDs today fluoresce, converting only about 25 percent of their energy into light, but our platinum-rich polymer is phosphorescent too, allowing us to recover come of the remaining 75 percent of electrical energy,” said Vardeny. The next step for the researchers is to experiment with different spacings between the platinum atoms in the polymer interchain, as well as to experiment with other heavy molecules besides platinum. To date, the researchers have produced two materials -- one with a platinum atoms between every link in the interchain -- resulting in violet and yellow light, the other inserted a platinum atom between every third link, resulting in blue and orange light. The hope is that a polymer with various spacings between platinum atoms can produce all the wavelengths in white light. “The ultimate goal is to create white light. Unfortunately, white light is very not well defined, but essentially we want to emit all colors,” said Vardeny. The platinum-rich polymer today must be stimulated by light to work, but once the formula for a white-light polymer is defined, the researchers will fashion an OLED material out of it that emits in response to electrical stimulation. The researchers estimate about a year will be needed to perfect the white-light emitting polymer and another two to convert it into an OLED. The researchers also plan to apply the technique to creating a new type of solar cell. And because platinum-rich polymers allow information to be stored on the spin of electrons, the material has the potential to create a new type of memory chip. TSMC Releases 16nm FinFET design flows By Peter Clarke Leading pure-play foundry Taiwan Semiconductor Manufacturing Co. Ltd. has announced the existence of three reference design flows for FinFET and 3D-stacked ICs that have been taken to silicon. The silicon validation of these flows signifies the opening up of the manufacturing processes for the design of production volume chips. Intel was the pioneer of the FinFET in commercial production and remains the only company with such a manufacturing process. However, TSMC is reported to have signed to supply Apple with processors on a three-year contract that will include some FinFET. The three TSMC design flows are: a digital design flow for TSMC’s 16FinFET process; a custom design flow for 16FinFET that offers transistor-level design of analog, digital, mixed-signal, custom digital and memory; and a 3D-IC flow for the design of vertically stacked structures and multi-die assemblies. EDA software vendors collaborated with TSMC to develop and validate these design routes using silicon test vehicles, TSMC said in a press release. However, TSMC did not indicate which companies’ tools had been proved effective at which stages of the design process. The 16-FinFET digital design flow uses the Cortex-A15 multicore processor, licensed from ARM Holdings plc, as its validation vehicle for certification. It helps designers adopt the FinFET by addressing such issues as RC modelling, power-performance area trade-offs, low-vdd operation, electro-migration, and power management. Integrating multiple components in a single stacked component can provide benefits in terms of physical scaling and power consumption. TSMC’s 3D-IC design flow addresses such items as through-transistor-stacking (TTS) technology; through silicon vias (TSVs) plus microbumps, back-side metal routing; and TSV-to-TSV coupling extraction. “These reference flows give designers immediate access to TSMC’s 16FinFET technology and pave the way to 3D-IC Through-Transistor-Stacking (TTS) technology,” said Cliff Hou, vice president of R&D at TSMC. www.electronics-eetimes.com Electronic Engineering Times Europe October 2013 17


EETE OCT 2013
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