Organic Light-emitting Diode Lighting Research Articles

Single-molecule electroluminescence and photoluminescence of polyfluorene unveils the photophysics behind the green emission band

Optoelectronic properties of polyfluorene, a blue light-emitting organic semiconductor, are often degraded by the presence of green emission that originates mainly from oxidation of the polymer. Here, we use single-molecule electroluminescence (EL) and photoluminescence (PL) spectroscopy on polyfluorene chains confined in vertical cylinders of a phase-separated block copolymer to spectrally resolve the green band and investigate in detail the photophysical processes responsible for its appearance. In both EL and PL, a substantial fraction of polyfluorene chains shows spectrally stable green emission which is ascribed to a keto defect. In addition, in EL, we observe a new type of vibrationally resolved spectra distributed over a wide range of frequencies and showing strong spectral dynamics. Based on quantum chemical calculations, this type is proposed to originate from charge-assisted formation and stabilization of ground-state aggregates. The results are expected to have broad implications in the fields of photophysics and material design of polyfluorene materials.

Analysis of electroluminescence degradation for organic light-emitting diode using a rate equation of chemical kinetics

Light intensity degradation is one of the most important parameters in the design of organic light-emitting diodes (OLEDs) for image applications, and it is usually obtained through time-consuming stability tests. The lifetimes are estimated based on the well-known empirical reciprocal relationship between the initial brightness and the half-lifetime, which is assumed to be always valid for all devices. In this work, it was used as a chemical kinetics approach for modeling the light output in time under constant current operation. Through this approach, an equation with only two parameters, one for OLED light output in time and another for half-lifetimes, was obtained. This approach was applied to stability tests for three different OLEDs to determine how their features affect the kinetic parameters and to compare such parameters for OLEDs operating at two temperatures, 22°C and 70°C, to determine if they have a correlation with thermal stability.

Barrier properties of plastic films coated with an Al2O3 layer by roll-to-toll atomic layer deposition

Thin (30–40nm) and highly uniform Al2O3 coatings have been deposited at relatively low temperature of 100°C onto various polymeric materials employing the atomic layer deposition (ALD) technique, both batch and roll-to-roll (R2R) mode. The applications for ALD have long been limited those feasible for batch processing. The work demonstrates that R2R ALD can deposit thin films with properties that are comparable to the film properties fabricated by in batch. This accelerates considerably the commercialization of many products, such as flexible, printed electronics, organic light-emitting diode lighting, third generation thin film photovoltaic devices, high energy density thin film batteries, smart textiles, organic sensors, organic/recyclable packaging materials, and flexible displays, to name a few.

Low-haze light extraction from organic light-emitting diode lighting with auxiliary electrode by selective microlens arrays

Improved out-coupling efficiency and low haze of organic light-emitting diode (OLED) lighting with an auxiliary electrode are demonstrated by selective microlens arrays (SMLAs). The microlens arrays, aligned with the auxiliary electrode, were selectively fabricated, since the fully packed microlens arrays lead to OLED lighting with high haze. The external quantum efficiency and power efficiency of the devices with the SMLAs increased by 32% when compared with the devices without these arrays. Using the SMLAs, dark grid lines in the emission region became brighter, with a low haze, and the spectra of the emitted light had no shift.

68.2: Lowering Cost for OLED Lighting Manufacturing

AbstractManufacturing of Organic Light Emitting Diodes (OLED) for lighting is still some distance from the industry recognized cost target of 100 € /m2. Within the government funded Light In‐Line (LILi) project, a team of material supplier, machine manufacturers and basic researchers have investigated potential ways to reduce OLED manufacturing costs. The concept developed within the LILi‐project shows that a competitive cost structure can now be reached.

Self-Aligned Integration of Spin-Coated Organic Light-Emitting Diodes and Photodetectors on a Single Substrate

We present a self-aligned optical all integrated measurement section on a single substrate consisting of an organic light-emitting diode (OLED) as light source and an organic photodetector (OPD), both fabricated by spin-coating. Areas of the layers, that are not required, are removed by an oxygen plasma treatment. No additional shadow mask is used in this self-aligned structuring process as the metal cathodes protect the underlying organic layers. The functionality of the optoelectronic components is maintained. The devices are characterized by current-voltage (I-V) and spectral measurements. The modulation of the OLED light intensity is detected at the OPD by a significant increase of the photo current.

Large white organic light-emitting diode lighting panel on metal foils

Large-area top-emitting PIN structure (highly p- and n- type doped transport layers for electrons and holes and an undoped emitter layer)-organic light-emitting diode (OLED) on advanced metal foils were fabricated for lighting applications. ArcelorMittal has developed a new surface treatment on metal foils, suitable for roll-to-roll production and dedicated to large-area device integration. Both monochromatic and white devices are realized on advanced metal foils. Power efficiencies at 1000 cd/m 2 of >70 lm/W (green), moreover, power efficiency of white devices of >22 lm/W are achieved. Furthermore, first large-area 60 × 60 cm white OLED sources on metal foils are presented. C 2011 Society of Photo-Optical Instrumentation Engineers

An open pilot study of ambulatory photodynamic therapy using a wearable low-irradiance organic light-emitting diode light source in the treatment of nonmelanoma skin cancer

Photodynamic therapy (PDT) is a popular treatment for nonmelanoma skin cancer with clearance rates of between 70% and 100%. Although reported to have a superior cosmetic outcome, the inconvenience of hospital visits and discomfort during therapy are considered drawbacks. To present an open pilot study of a low-irradiance, potentially disposable, lightweight, organic light-emitting diode (OLED), which is an area-emitting light source (2 cm diameter), suitable for ambulatory PDT. Twelve patients with Bowen's disease (eight) and superficial basal cell carcinoma (four) < 2 cm in diameter were recruited into the study following histological confirmation of the diagnosis. Two treatments (45-60 J cm(-2) red light, 550-750 nm, peak 620 nm, irradiance 5 mW cm(-2)) were administered 1 month apart following application of aminolaevulinic acid for 4 h. At the 12-month follow-up, seven of the 12 patients remained clear, with four of the nonresponders demonstrating peripheral margin failure. Patients were scored for pain during and immediately after treatment using the numerical rating scale (NRS; 1-10). All 12 subjects scored pain as < 2 using the NRS (median score 1). In contrast, a similar cohort of 50 consecutive patients from our routine PDT clinic (Aktilite inorganic LED source; 75 J cm(-2), irradiance 80 mW cm(-2)) scored a median of 6 on the NRS. Pain and inconvenience are practical barriers to the use of conventional PDT. This pilot study suggests that OLED-PDT is less painful than conventional PDT with the added advantage of being lightweight, and therefore has the potential for more convenient 'home PDT'. These results need to be validated in larger studies.