Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array

• Published in: Journal of optics. A, Pure and applied optics Vol. 10; no. 5; pp. 055302 - 055302 (9)
• Main Authors: Wei, Mao-Kuo, Lee, Jiun-Haw, Lin, Hoang-Yan, Ho, Yu-Hsuan, Chen, Kuan-Yu, Lin, Ciao-Ci, Wu, Chia-Fang, Lin, Hung-Yi, Tsai, Jen-Hui, Wu, Tung-Chuan
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.05.2008; Institute of Physics
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Lenses, prisms, and mirrors; Optical elements, devices, and systems; Optical waveguides and coupleurs; Optics; Optoelectronic devices; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Microlens arrays; organic light-emitting device; Spectral line shift; Fill factor; Microoptics; Microlens; luminous power efficiency; Optical properties; Organic light emitting diodes; height ratio; Optical waveguide; Organic light-emitting devices; luminous current efficiency
• ISSN: 1464-4258; 1741-3567
• DOI: 10.1088/1464-4258/10/5/055302

In this paper, we present and analyze the influences of the fill factor and the sag of hexagon-based microlenses on the optical characteristics of an organic light-emitting device (OLED), such as spectral shift, CIE (abbreviation of the French 'Commission internationale de l'eclairage') coordinates, viewing angle dependence, luminous current efficiency and luminous power efficiency. Both the luminous current efficiency and luminous power efficiency of the OLED were found to increase linearly on increasing the fill factor of the microlenses. It is also found that the full width at half maximum (FWHM) of the OLED spectra and CIE coordinates decreased linearly on increasing the fill factor of the microlenses. Besides, the efficiency improvement of the OLED increased with the height ratio of attached microlenses. Compared to the OLED, the luminous current efficiency and luminous power efficiency of the device can be enhanced by 35% and 40%, respectively, by attaching a microlens array having a fill factor of 0.90 and a height ratio of 0.56. We also observed blue shifts at different viewing angles when microlens arrays were attached to the OLED, which is evidence that the waveguiding modes are being extracted. In our planar OLED, the peak wavelength blue shifted and the FWHM decreased on increasing the viewing angles, due to the microcavity effect.