Donald Franklin Foust

Organic light-emitting devices for illumination quality white light

A method of generating white light by combining a blue organic light-emitting diode with a down-conversion phosphor system is presented. It is demonstrated that the use of the down-conversion phosphor system actually leads to an overall power efficiency increase, an effect attributed to the high quantum efficiency of phosphor materials and the presence of light scattering in the phosphor layers. It is also shown that this approach permits the generation of illumination quality white light over the full range of color temperatures required for lighting applications. For the model device demonstrated in this work, an overall electrical to optical power conversion efficiency of 1.3% was achieved at a brightness of 1080 cd/m 2 .

A Transparent, High Barrier, and High Heat Substrate for Organic Electronics

The use of plastic film substrates for organic electronic devices promises to enable new applications, such as flexible displays and conformal lighting, and a new low-cost paradigm through high-volume roll-to-roll fabrication. Unfortunately, presently available substrates cannot yet deliver this promise because of the challenge in achieving the required combination of optical transparency, impermeability to water and oxygen, mechanical flexibility, high-temperature capability, and chemical resistance. Here, we describe the development and performance of a plastic substrate comprising a high heat polycarbonate film combined with a unique transparent coating package that is aimed at meeting this challenge.

Fault-tolerant, scalable organic light-emitting device architecture

High performance organic light emitting diodes (OLEDs) become problematic as emitting area increases due to the high resistivity of the transparent electrode and the increasing probability of encountering a catastrophic short-circuit defect during fabrication. In this letter, a monolithic series-connected OLED architecture is demonstrated. It is shown that such devices exhibit the same power efficiency as traditional small area OLEDs but are, in addition, relatively insensitive to electrode resistivity and tolerant to normally catastrophic short-circuit defects. This architecture should enable applications such as lighting where scalability to large emitting area without high fabrication cost or design complexity is required.

Aqueous pretreatments of polyetherimide to facilitate the bonding of electrolessly deposited copper

A chemical method for pretreating polyetherimide substrates to promote adhesion to copper is described. The process consists of cleaning the polymer surface followed by surface normalization, debris solubilization, and adhesion promotion via chemical modification of the polymer surface. Classes of candidates for each of the major steps are described and the optimal agents assembled into a recommended procedure. Peel strengths between 150-210 g mm-1 for copper to polyetherimide were achieved utilizing the suggested scheme. Scanning electron microscopic and X-ray photoelectron spectroscopic analyses were employed to investigate changes in the polymer surface and chemistry during processing. Metallized specimens were examined after 90° peel testing and the failure locus found to be within the polymer layer.

4.1: Invited Paper: Large Area White OLEDs

A large area white OLED panel that emits 1200 lumens of illumination-quality light is described. The technical approach utilizes down-conversion from an underlying blue OLED made with a fault-tolerant monolithically series-connected architecture. The high device efficiency suggests that the singlet/triplet ratio for polymer OLEDs can be greater than 25%.

Copper deposition onto polyetherimide: Interface composition and adhesion

The chemical composition and adhesion of the interface between copper (applied via an electroless bath or by vacuum evaporation) and polyetherimide substrates are investigated. Electroless copper deposition requires a chemical pretreatment to ensure final adhesion values of 180–220 g/mm, whereas comparable adhesion is obtained for evaporated copper without pretreatment. Both metallization methods require a postdeposition heat treatment to maximize the copper/polyetherimide adhesion. The interface side of the metal deposits are exposed by a substrate dissolution technique and analyzed using x‐ray photoelectron spectroscopy. A thin (∼30 A) insoluble polymer layer remains which is believed to chemically interact with the metal. In addition, interfacial oxidation of the metal deposit increases with the application of the heat treatment. The role of this interfacial chemistry on copper/polyetherimide adhesion is discussed.

OLEDs for lighting: new approaches

OLED technology has improved to the point where it is now possible to envision developing OLEDs as a low cost solid state light source. In order to realize this, significant advances have to be made in device efficiency, lifetime at high brightness, high throughput fabrication, and the generation of illumination quality white light. In this talk, the requirements for general lighting will be reviewed and various approaches to meeting them will be outlined. Emphasis will be placed on a new monolithic series-connected OLED design architecture that promises scalability without high fabrication cost or design complexity.

Aqueous pretreatment of polyetherimide to facilitate the bonding of electrolessly deposited metals. Part 2: Solubilizer-free systems

An aqueous method for chemically pretreating polyetherimide substrates to promote adhesion to electrolessly deposited copper or nickel is described. The process consists of cleaning the polymer surface followed by surface normalization and debris removal. In contrast to previously developed processes, no separate adhesion promotion step is required. Peel strengths between 150-250 and 120-150 g/mm were achieved for copper and nickel, respectively. Scanning electron microscopy and X-ray photoelectron spectroscopy were utilized to investigate changes in the polymer surface morphology and chemistry during processing. Possible candidates for the different steps are presented, as are analyses of the failure loci following peel strength assessment.

Thermal reliability of the metal/polyetherimide bond

Recent advances in the pretreatment of polyetherimide surfaces have enabled the deposition of adherent metal coatings. The bond between the metal and plastic has been found to be predominantly chemical in nature. The thermal reliability of the metal/polymer bond was evaluated in accelerated aging tests. The metal/polyetherimide bond was found to be insensitive to prolonged contact (200 h) to 65°C and 100% relative humidity (RH) environments or 85°C and dry or 85% RH conditions. Thermal and humidity cycling (IBM 4.4.16) had no effect on either the metal/ polymer bond strength or the surface resistivity of the metal coating. Exposing metallized specimens to extreme and rapid thermal changes, +150°C to -196°C and less than 15 s transfer time between temperatures, further revealed the durability of the bond. Exposure to simulated soldering conditions representing multiple dwells at temperatures between 232 and 288°C and times of 5 or 10 s had no effect on adhesion. The importance of a prebake prior to solderi...

Illumination-quality OLEDs for lighting

OLED technology has improved to the point where it is now possible to envision developing OLEDs as a low cost solid state light source. In order to realize this, significant advances have to be made in device efficiency, lifetime at high brightness, high throughput fabrication, and the generation of illumination quality white light. In this talk, a down conversion method of generating white light is demonstrated and shown to be capable of generating illumination quality white light over the full range of color temperatures required for lighting. It is also demonstrated that, due to the presence of light scattering, the down-conversion method can actually increase the overall device power efficiency.