Coherent mode coupling in highly efficient top-emitting OLEDs on periodically corrugated substrates.

Bragg scattering at one-dimensional corrugated substrates allows to improve the light outcoupling from top-emitting organic light-emitting diodes (OLEDs). The OLEDs rely on a highly efficient phosphorescent pin stack and contain metal electrodes that introduce pronounced microcavity effects. A corrugated photoresist layer underneath the bottom electrode introduces light scattering. Compared to optically optimized reference OLEDs without the corrugated substrate, the corrugation increases light outcoupling efficiency but does not adversely affect the electrical properties of the devices. The external quantum efficiency (EQE) is increased from 15 % for an optimized planar layer structure to 17.5 % for a corrugated OLED with a grating period of 1.0 µm and a modulation depth of about 70 nm. Detailed analysis and optical modeling of the angular resolved emission spectra of the OLEDs provide evidence for Bragg scattering of waveguided and surface plasmon modes that are normally confined within the OLED stack into the air-cone. We observe constructive and destructive interference between these scattered modes and the radiative cavity mode. This interference is quantitatively described by a complex summation of Lorentz-like resonances.

The Impact of Heterotopic Ossification on Self-Reported Outcomes After Total Hip Arthroplasty Using the Direct Anterior Approach.

BACKGROUND: Heterotopic ossification (HO) is a known finding after total hip arthroplasty (THA) that potentially affects clinical outcomes. The incidence of HO is related to various factors, including soft-tissue trauma, postoperative medication, surgical approach, and the surgeon's experience. Because use of the direct anterior approach (DAA) is gaining popularity, we aimed (1) to determine the incidence of HO after DAA-THA and (2) to evaluate the impact of HO on patient-reported outcomes (PROs). METHODS: We retrospectively reviewed 401 THAs (67 ± 10 years old, 210 men). The incidence and grade of HO were evaluated using the Brooker classification with anteroposterior and lateral radiographs. PROs were collected with use of the Oxford Hip Score (OHS) and the Core Outcome Measures Index (COMI)-Hip and were correlated with HO grades using generalized multiple regression models. RESULTS: The incidence of HO was 29.9% on the anteroposterior radiographic views (Brooker grade 1, 14.5%; grade 2, 11.1%; grade 3, 2.7%; and grade 4, 0.57%); the lateral radiographic views detected 9% additional HO when compared with the anteroposterior radiographs alone (Brooker grade 1, 8%, and grade 2, 1%). HO was more frequent in men. The American Society of Anesthesiologists (ASA) grade, age in women, and higher body mass index (BMI) in men were associated with higher HO grades. A transverse "bikini" incision was associated with a lower rate (4%) of Brooker grades 3 and 4 HO when compared with a longitudinal incision (12%). A Brooker grade of 0 to 3 HO did not impact outcomes. Only Brooker grade-4 HO was associated with significantly worse PROs; however, pain was not affected. CONCLUSIONS: Low-grade HO after DAA-THA is not uncommon, and its rate is underestimated when anteroposterior radiographic views are evaluated without lateral views. The risk factors for developing HO in our cohort were an ASA grade of >3, male sex (especially with a high BMI), older age in women, and use of longitudinal incisions. With use of the bikini incision, patients had lower rates of severe HO, but mostly senior surgeons with more experience performed their surgery. Age, ASA grade, experience level of the surgeon, and Brooker grade-4 HO all had a significant influence on PROs. Clinically important HO (Brooker grade 4) remains rare after DAA-THR. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Three-terminal RGB full-color OLED pixels for ultrahigh density displays.

In recent years, the organic light-emitting diode (OLED) technology has been a rapidly evolving field of research, successfully making the transition to commercial applications such as mobile phones and other small portable devices. OLEDs provide efficient generation of light, excellent color quality, and allow for innovative display designs, e.g., curved shapes, mechanically flexible and/or transparent devices. Especially their self emissive nature is a highly desirable feature for display applications. In this work, we demonstrate an approach for full-color OLED pixels that are fabricated by vertical stacking of a red-, green-, and blue-emitting unit. Each unit can be addressed separately which allows for efficient generation of every color that is accessible by superpositioning the spectra of the individual emission units. Here, we use a combination of time division multiplexing and pulse width modulation to achieve efficient color mixing. The presented device design requires only three independently addressable electrodes, simplifying both fabrication and electrical driving. The device is built in a top-emission geometry, which is highly desirable for display fabrication as the pixel can be directly deposited onto back-plane electronics. Despite the top-emission design and the application of three silver layers within the device, there is only a minor color shift even for large viewing angles. The color space spanned by the three emission sub-units exceeds the sRGB space, providing more saturated green/yellow/red colors. Furthermore, the electrical performance of each individual unit is on par with standard single emission unit OLEDs, showing very low leakage currents and achieving brightness levels above 1000 cd/m2 at moderate voltages of around 3-4 V.