Optical performance characterization of curved OLED light sources

Abstract

Bending a planar organic light‐emitting diode (OLED) alters the optical structure of the device, resulting in the change of optical characteristics. The bending effect on light emission through the substrate was analyzed, and the issues were extracted. The effect of curvature radius on characteristics of nonplanar OLED light sources was experimentally studied. For this purpose, two OLED samples with barrier layer thicknesses of 100 and 150 nm were fabricated, and their characteristics were measured at curvature radii of R0 = ∞ mm (flat state), R2 = 143 mm (cylindrically curved state), and R5 = 56.7 mm (cylindrically curved state). The variations in optical characteristics such as total luminous flux, the luminous intensity pattern, and the spectrum were verified by measuring the cylindrically shaped OLEDs. The results were evaluated and discussed for OLEDs in cylindrically curved states.

23‐2: Characterization of Directional Chromaticity of Cylindrically Curved OLED

“…To measure the characteristics of the samples in planar and cylindrically curved states, three jigs with cross sections shaped as segments of circles were designed and fabricated with radii of R0= mm (a planar with a curvature of C0=0 m -1 , and a height of segment, H0=0 mm), R2=143 mm (with a curvature of C2=17.637 m -1 , a height of segment, H2=2 mm) and R5=56.7 mm (with a curvature of C5=6.993 m -1 , and a height of segment, H5=5 mm) as shown in Fig. 6(a),(b),(c) [1][2][3][4][5][6][7]. The planar jig was fabricated as a base for the comparison of the results.…”

“…The difference between a cylinder and a sphere is that the analysis is based on the azimuth angle (), i.e., the position of the refracted ray on the inner or outer surface of the cylindrical OLED. The transmission and reflection characteristics are expressed in terms of the inner and outer radii of the cylindrical OLED and the azimuth angle () [1].…”

“…The flexible OLEDs are totally different in shape from the light sources that have been widely used so far. When a planar light emitting surface is bent or deformed, the optical properties of the device such as the total luminous flux and the luminous intensity distribution change [1]. In contrast to planar OLEDs, the non-planar OLEDs (e.g.…”

Optical characterization of curved organic light emitting diodes with different thicknesses of barrier layers and cylindrical radii of curvatures

“…The following OLED samples were prepared and used for measuring and evaluating their optical characteristics in planar and bent states. 14 The sample S#0, with glass substrate (thickness: 500 μm) was fabricated for comparison of the characteristics. The samples S#1 and S#2 were fabricated to have PEN substrates and to have barrier layer (SiN) thicknesses of t 1 = t 2 = 100 nm.…”

“…In contrast to planar OLEDs, the non-planar OLEDs introduce new measurement issues and challenges. [14][15][16][17][18][19] In this paper, the effect of substrate thickness on the optical characteristics of an OLED in bent state are almost theoretically studied. In the next step the remaining issue, that is, the OLED's chromaticity change with the viewing direction in planar and bent states are experimentally studied by fixing the OLED on the curved jigs.…”