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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.techfore.2009.02.003 Byline: Fang-Mei Tseng (a), Ai-Chia Cheng (a), Yi-Nung Peng (b) Keywords: Scenario analysis; Delphi; Technological substitution model; OLED TV Abstract: The technological substitution model, proposed in 1971, was designed to analyze the penetration process of new-generation technologies replacing old ones. It was expanded in 1979 to consider more than two generations and the substitution process among various entities in the market. However, this expanded model is often limited by a relative lack of data on the latest-generation technology. On the other hand, scenario analysis, as another breed to forecasting tool, provides rich and complex portraits of possible future development of technologies. However, it fails to provide quantifiable forecasts. Therefore, previous researchers combined these two methods to analyze the development of new technologies. Nevertheless, to make forecasting more holistic, the current opinions of seasoned experts should also be taken into account. However, because of the often-diverged expert opinions, a method for consensus building, such as the Delphi method, is also necessary. Therefore, we combined the scenario analysis with the Delphi method and the technological substitution model to analyze the development of a new technology, namely, the latest-generation television (TV), or the organic light-emitting diode (OLED) TV. We elaborate three possible scenarios, and forecast the market share of OLED TV and four other TV technologies in the global market over the next 10 years: cathode ray tube, rear projection, plasma display panel, and liquid crystal display. Author Affiliation: (a) Department of International Business, Yuan Ze University, 135 Yuan-Tung Rd., Chung-Li, Taoyuan 320, Taiwan (b) Department of Business Administration, Yuan Ze University, 135 Yuan-Tung Rd., Chung-Li, Taoyuan 320, Taiwan Article History: Received 6 January 2009; Revised 21 February 2009; Accepted 23 February 2009

A comprehensive optical model for dual wavelength LEDs is developed using optical ray tracing programs. Optical dispersion of GaN, InGaN, and AlGaN is also included in this numerical model. The light extraction efficiency of LEDs can be calculated based on LED structure and material properties. Moreover, a LED device structure can be optimized to improve the light extraction efficiency. OCIS codes: 250.0250, 230.3670.

In practice, any cluster of light-emitting diodes (LEDs) can be modeled or measured as a directional point source if the detector is far enough away from the cluster. We propose a far-zone condition for measuring or modeling propagation of light from an LED array. An equation gives the far-field distance as a function of the LED radiation pattern, array geometry, and number of LEDs. The far field is shorter for high packaging density clusters, and the far field considerably increases with increasing beam directionality of LEDs. In contrast with the classical rule of thumb (5 times the source size), the near zone of an array with highly directional LEDs can extend to more than 60 times the array size. We also analyze the effect of introducing random variations of light flux among LEDs of the array, which shows that far-field variability is low in high packaging density arrays. OCIS codes: 230.3670, 120.5630, 120.5240, 120.4800, 150.2945.

Light extraction from two-dimensional objects is discussed. Analytical calculations in terms of three different parameters have been applied to equiangular polygons to trace light rays during multiple reflections in a polygon. Based on the result that there are a finite number of incident angles in a polygon for a light ray, it was found that the triangle has the least chance to trap light rays among the polygons. The discussion has been extended to parallelograms, which have an advantage in light extraction to rectangles. Placement of a possible light source in polygons is discussed. OCIS codes: 250.0250, 160.6000.

We present here a computer program - the Semiconductor Device Simulator - which simulates the working of three p-n junction devices: the light-emitting diode, the solar cell, and the tunnel diode. This program enables students to create the device starting with two pieces of intrinsic semiconductor material, and doping them appropriately to create a p-n junction device of their choice. While creating the device, students can observe the changes in the energy bands and Fermi level as a response to doping. The device, once created, can then be incorporated into a circuit where the students can observe the energy bands, the I-V graph, as well as the intensity spectrum of the device in response to the changes in applied voltage and/or incident light. No prior knowledge of higher level mathematics is required to use the program. The program is available for Windows[TM] and Macintosh[TM] platforms. The flexibility of the program allows it to be used by students over a range of academic levels. We have field tested the program along with associated materials in both high school and university environments. The current version of the program contains modifications based on these field tests.

In this paper, we present a theoretical study and a numerical simulation of a classical long wavelength top illuminated PIN photodetector for microwave applications under very high optical power. The modeling includes a monodimensional drift-diffusion model for the device and takes into account the external circuit. At first, this modeling is validated using experimental results from the literature. Second, we consider a classical InP/GaInAs/InP photodiode grown on [N.sup.+] InP substrate. The presented results show that the distortion and the saturation of the microwave signal at 20 GHz are due to the space F charge effect in the photodetector and also to the depolarization of the device because of the external circuit. The main parameter influencing these phenomena are the optical power, the bias voltage, the optical spot c width and the modulation depth. In case of small optical spot, the effect of the external circuit is neglectable, while it contributes to the decrease of the microwave responsivity in case of large spot. The maximum output power is calculated in different cases and we can expect up to 12 dBm microwave output power for a 5 V reverse bias voltage.

A one-dimensional numerical model for the quantitative simulation of multilayer vapor deposited organic light emitting diodes (OLEDs) based on ssmall functional molecules was developed. The proposed model exhibits OLEDs' bipolar charge carrier drift with field-dependent mobilities and space charge effects, charge carrier diffusion, trapping, bulk and interface recombination, singlet exciton diffusion and quenching effects.