: Non-doped white organic light-emitting diodes using an ultrathin yellow-emitting layer of rubrene (5,6,11,12-tetraphenylnaphtacene) inserted on either side of the interface of a holetransporting α-NPB (4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl) layer and a blue-emitting DPVBi (4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl) layer are described. Both the thickness and the position of the rubrene layer allow fine chromaticity tuning from deep blue to pure yellow via a bright white (WOLED) with CIE coordinates (x= 0.33, y= 0.32), a η ext of 1.9%, and a color rendering index (CRI) of 70. Such a structure also provides an accurate sensing tool to measure the exciton diffusion length in both DPVBi and NPB (8.7 and 4.9 nm respectively). Organic light emitting devices (OLEDs) are a promising technology for fabrication of full-color flatpanel displays. The development of OLEDs relies on the capability to obtain emission spanning the full visible spectrum. In particular, White OLEDs (WOLEDs) are of foremost interest for lighting and display applications 1 . To achieve white emission, various methods have been used, such as e.g. excimer/exciplex emission 2 , mixing of three (red, blue, green) or two (complimentary) colors in a single host matrix  or in physically separate layers 3 . Among these various devices, numerous doped-type WOLEDs using two mixed complimentary colors to produce white have been fabricated 4,5 . Although the co-evaporation process allows to a certain extent a control of the emitted radiation color via the different evaporation rates, it remains technologically difficult to accurately control the concentration. Hence, fine tuning of the color and achievement of bright white emission remain problematic. We report in this letter on a way to finely tune the color, including balanced white emission, in a multilayer non-doped OLED 6,7 based on blue matrices, in which an ultrathin yellow emitting layer was inserted. We show that by adjusting both the thickness and position of this layer, a very accurate control of the emitted color can be obtained, from deep blue with CIE coordinates (0.17, 0.15) to pure yellow (0.51, 0.48), via a bright white (0.32, 0.31) close to the equi-energy white point (0.33, 0.33), and a quite good Color Rendering Index (CRI) of 70. The external quantum efficiencies, the chromaticity coordinates and the luminance values are investigated for various thicknesses and positions of the yellow-emitting layer. Finally, the device structure, sometimes referred as "delta doping" 8 , allows a better understanding of the emission process through an experimental determination of the exciton lengths.The 0.3 cm 2 -active-surface OLED-structure consists of the different layers described in fig. 1. The Indium Tin-Oxide (ITO)-covered glass substrate was cleaned by sonication in a detergent solution, then in deionized water and prepared by a UV-ozone treatment. Organic compounds were deposited onto the ITO anode by sublimation under high vacuum (10 -7 Torr) at a rate of 0.1 -0.2 nm/s. An ...

In this paper we present a high resolution analysis of xenon–rare gas absorption spectra in the far uv region between 1150 and 1500 Å. We give also the first quantitative results on the pressure and temperature dependence of absorption. These results may be used to discuss the origin of the many satellite bands observed in the proximity of resonance and forbidden atomic xenon lines. Information on the lowest excited XeKr and XeAr potential curves is obtained from this work.

A quantitative analysis of absorption by Xe2 pairs in the wings of the two first resonant lines (1469.6 and 1295.6 Å) is presented as a function of pressure (P<760 Torr) and temperature (130 K<T<300 K). Using a quasistatic theory, absorption measurements provide valuable information on the lowest 0u+ and 1u excited states, the 0g+ ground state potential being known from literature. In the near wing region (‖Δν‖<100 cm−1) the shape of the line wings is used as a probe of the asymptotic −2C3/R3−C60/R6 (0u+) and +C3/R3−C61/R6 (1u) potentials assuming at large R a constant oscillator strength, C3 and C6 excited constants are determined. Furthermore the dependence of absorption with temperature is used to derive additional information about the upper states and also to put in evidence some variation of transition moments, at shorter internuclear distances (3.7 Å <R<4.6 Å). The potential curves experimentally derived are compared with ab initio calculated curves.