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Tech Front: Hybrid Semiconductor Phosphors Emerge for Low-Cost LED Lighting


A team of researchers at Rutgers University (Piscataway, NJ) have designed new materials that could change the way household light bulbs are manufactured. With the phase-out of traditional incandescent light bulbs in the US and other countries, lighting manufacturers have looked for more energy-efficient lighting alternatives in the form of light-emitting diodes (LEDs). But LED manufacturing to date has required the use of rare-earth elements that are either increasingly more expensive or difficult to obtain.

The research team, led by Jing Li in Rutgers’ Department of Chemistry and Chemical Biology, has designed new materials for LED manufacturing without using rare-earth elements, and have described their developments in a report published by the American Chemical Society. Their paper, “Systematic Approach in Designing Rare-Earth-Free Hybrid Semiconductor Phosphors for General Lighting Applications,” was published Sept. 12 in the ACS Journal of the American Chemical Society.

LED lighting is an energy-efficient alternative to more conventional lights. They also last years longer. Switching to LED lighting over the next two decades “could save the country $250 billion in energy costs over that period, reduce the electricity consumption for lighting by nearly one half, and avoid 1800 million metric tons of carbon emission,” according to the US Department of Energy. Although white LEDs are already available, their light is generally perceived as colder or harsher than the warm glow of traditional incandescents, and most of these lights contain the rare earth elements that are in high demand for many high-tech devices, which adds to the cost of the technology. Jing Li’s research team set out to solve the issues of material sources and pricing.

A new way to make white and colorful LEDs that cost less than current LEDs is still more environmentally friendly than traditional lighting methods.

At the present time, commercially available white light emitting diodes (WLEDs) are predominantly phosphor-based (a yellow-emitting phosphor, such as cerium-doped yttrium aluminum garnet, coupled with a blue-emitting InGaN/GaN diode), which rely heavily on rare-earth metals. To avoid potential supply issues with these elements, the researchers developed an inorganic-organic hybrid phosphor family based on I–VII binary semiconductors.

The researchers designed a family of materials made out of an abundant compound, copper iodide. The team tuned them to glow a warm white shade or various other colors using a low-cost solution process. “Combining these features, this material class shows significant promise for use in general lighting applications,” the scientists conclude.

The hybrid phosphor materials can be synthesized by a simple, low-cost solution process and are easily scalable. Their band gap and emission energy, intensity, and color can be systematically tuned by incorporating ligands with suitable electronic properties. High quantum efficiency is achieved for some of these compounds. Such features make this group of materials promising candidates as alternative phosphors for use in general lighting devices.

The paper’s authors included Xiao Zhang, Wei Liu, George Z. Wei, Debasis Banerjee, Zhichao Hu, as well as Jing Li. The research was funded by the National Science Foundation. For more information, see ME

The Soft(ware) Side of Manufacturing

The concept of a manufacturing system, as explained in M. Eugene Merchant’s 1981 paper, “Importance and Role of Computer Integrated Manufacturing” (TP81PUB37), brought forward the tremendous potential of computers to integrate the various bits and pieces of manufacturing activity as well as the entire system of manufacturing. Computers provided manufacturing with two powerful capabilities never before available—online variable programming (flexible automation) and online moment-by-moment optimization—for both the “hard” components of manufacturing (machinery and equipment) and the “soft” side of information flow, databases and so on.

The changing balance between problem solving in hardware and software and the decentralization of computer systems were major trends that had a significant influence on the data processing systems used in industry (TP72PUB226). Decentralized computers may seem incongruous to the goal of an integrated system, but it is the data structure linking the solutions found by each computer subsystem that provides the backbone of manufacturing system success.
Composite ply with darts, and corresponding flat pattern (O. Guillermin, TP04PUB105)
In “Manufacturing Software Development and Application” (TP72PUB65), the author from IBM explains how full utilization of computers met initially with two impediments. First, while much time and effort was spent to make production workers more productive, the potential of managerial, professional and technical workers (known by Peter Drucker’s phrase, “knowledge workers”) had to be harnessed as a source of new and innovative ideas for direct workers to produce with computer assistance. The second blockage mentioned was the need to become as effective at managing computer installations and usage as for any other capital investment.

Object-oriented, software-centric and hardware-independent CNC control is discussed in TP95PUB158. The open system architecture described, which uses the power of low-cost PCs, creates the possibility for software design differentiation as opposed to hardware design differentiation. Also covered are the technical challenges of the open approach and the business challenges for vendors contemplating commercialization of open-architecture controls.


Implementation and Necessity

Early adopters of CIM found that for each problem solved there were 10 more demanding problems uncovered (TP84PUB383). For example, developments in robotics moved from offline programming for handling workpieces in a machining environment to assembly with multiple robots for variable shape components. Robot manufacturers had to develop supercomputers to perform three-dimensional pattern recognition at high speed from visual and tactile information received from “see” and “touch” sensors.

MRP II software implementation (TP88PUB561) had its share of bumps, too. After many months of effort, some companies were frustrated that while the old system was providing the main decision-making data, some departments were still supporting both systems and still other departments had rejected the new system. Lessons learned led to a methodology to make a clear and complete transition from old to new systems, implemented as a total solution with input in the evaluation and selection phases from all departments.

Economic conditions and increased competition forced parts cost estimating (TP91PUB436) from a “pull it out of a hat” method to one that incorporated costing standards (by which to evaluate new performance) and elements of product cost, including material, runner weight, regrind, workstation cost per hour, labor, tooling amortization, setup charges, cavitation and sales commission.

Sheetmetal Fabrication

A software tool is described in TP94PUB38 to assist in the design of preforms and rolls for near-net-shape profile rolling and profile ring rolling. Simplified analysis allows rapid design iterations and a better preliminary design before applying finite element analysis, reducing overall design cycle time.

As CAD/CAM for sheetmetal fabrication (TP96PUB4) evolved from a tool to make programs for numerically controlled punching machines to the heart of management information systems, managers became aware of the significant quality, productivity and sales advantages. Computer technologies related to CAD/CAM were instrumental to support machine tools, automatic unfolding, nesting, electronic data interchange, inspection and statistical process control. New software applications, such as production control and job tracking, that integrate with CAD/CAM helped overcome islands of automation in computer-integrated manufacturing and management systems.

Composite Structures

Making an informed design decision under a compressed development cycle and having to access data from many repositories is a difficult task for engineers and product designers. In TP04PUB105, software is described that provides tools to capture and communicate a complete product definition. An example with advanced continuous fiber composite materials highlights how risks, costs and development time are reduced through simulation. A knowledge-based, design-integrated virtual manufacturing software for laminated composites incorporates automated smart tools for producing a design for manufacturability using concurrent engineering concepts (TP04PUB123). The underlying composites processes are emphasized, and cost-effective robust designs with multiple alternatives can be generated and evaluated. ME

TechFront is edited by Senior Editors Patrick Waurzyniak,, and Ellen Kehoe,


This article was first published in the December 2014 edition of Manufacturing Engineering magazine. Click here for PDF.

Published Date : 12/1/2014

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