TechBlog

White organic light-emitting diodes offer a power efficiency, lifetime, and brightness that together constitute a significant advance toward viable devices for lighting.

Light-emitting diodes (LEDs) are used in both displays and illumination applications because they are small, robust, and potentially very efficient. Organic light-emitting diodes (OLEDs) continue to gain attention from the scientific and industrial community. In contrast to their inorganic counterpart, OLEDs are flat and diffuse area light sources with the device thickness being in the range of 1–2mm. Thus far, OLED development has been triggered mainly by applications in the display segment, starting with applications for MP3 music players, mobile phones, and other portable devices. Recently, Sony brought to market the first OLED TV, which indicates that a more general penetration of the display market is close at hand.

OLEDs have not yet entered the lighting market, but that will probably change soon. Already most of the big players in the field are preparing for OLEDs to become ‘the next big thing.’ However, several critical problems need to be solved before widespread use for lighting becomes feasible. Specifically, the lifetimes, power efficiencies, reliability, and cost-effectiveness of white OLEDs must be able to compete with existing lighting technologies.

Continue reading ‘Making highly efficient white light-emitting diodes’ »

Normally fragile and brittle silicon chips have been made to bend and fold, paving the way for a new generation of flexible electronic devices. The stretchy circuits could be used to build advanced brain implants, health monitors or smart clothing.

The complex devices consist of concertina-like folds of ultra-thin silicon bonded to sheets of rubber.

Writing in the journal Science, the US researchers say the chip’s performance is similar to conventional electronics. Continue reading ‘Silicon chips stretch into shape’ »

WEST LAFAYETTE, Ind. -

Engineers have created the first “active matrix” display using a new class of transparent transistors and circuits, a step toward realizing applications such as e-paper, flexible color monitors and “heads-up” displays in car windshields.

The transistors are made of “nanowires,” tiny cylindrical structures that are assembled on glass or thin films of flexible plastic. The researchers used nanowires as small as 20 nanometers - a thousand times thinner than a human hair - to create a display containing organic light emitting diodes, or OLEDS. The OLEDS are devices that rival the brightness of conventional pixels in flat-panel television sets, computer monitors and displays in consumer electronics.

Continue reading ‘Engineers make first ‘active matrix’ display using nanowires’ »

A simple surface treatment technique demonstrated by a collaboration between researchers at the National Institute of Standards and Technology (NIST), Penn State and the University of Kentucky potentially offers a low-cost way to mass produce large arrays of organic electronic transistors on polymer sheets for a wide range of applications including flexible displays, “intelligent paper” and flexible sheets of biosensor arrays for field diagnostics. In a paper posted this week, the team describes how a chemical pretreatment of electrical contacts can induce self-assembly of molecular crystals to both improve the performance of organic semiconductor devices and provide electrical isolation between devices.

Organic electronic devices are inching towards the market. Compounds with tongue-twisting names like “5,11-bis(triethylsilylethynyl) anthradithiophene” can be designed with many of the electrical properties of more conventional semiconductors. But unlike traditional semiconductors that require high-temperature processing steps, organic semiconductor devices can be manufactured at room temperature. They could be built on flexible polymers instead of rigid silicon wafers. Magazine-size displays that could be rolled up or folded to pocket size and plastic sheets that incorporate large arrays of detectors for medical monitoring or diagnostics in the field are just a couple of the tantalizing possibilities.

One unsolved problem is how to manufacture them efficiently and at low cost. Large areas can be coated rapidly with a thin film of the organic compound in solution, which dries to a semiconductor layer. But for big arrays like displays, that layer must be patterned into electrically isolated devices. Doing that requires one or more additional steps that are costly, time-consuming and/or difficult to do accurately.

Continue reading ‘Directed Self-Ordering Of Organic Molecules For Electronic Devices’ »