Journal of the Semiconductor & Display Technology (반도체디스플레이기술학회지)

The Korean Society Of Semiconductor & Display Technology (한국반도체디스플레이기술학회)
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Fabrication of Spherical Microlens Array Using Needle Coating for Light Extraction of OLEDs

니들 코팅을 이용한 OLED 광 추출용 구형 마이크로렌즈 어레이 제작

  • Kim, Juan (School of Energy Materials and Chemical Engineering, Korea University of Technology and Education) ;
  • Shin, Youngkyun (School of Electrical, Electronic & Communication Engineering, Korea University of Technology and Education) ;
  • Kim, Gieun (School of Electrical, Electronic & Communication Engineering, Korea University of Technology and Education) ;
  • Hong, Songeun (School of Electrical, Electronic & Communication Engineering, Korea University of Technology and Education) ;
  • Park, Jongwoon (School of Electrical, Electronic & Communication Engineering, Korea University of Technology and Education)
  • 김주안 (한국기술교육대학교 에너지신소재.화학공학부) ;
  • 신영균 (한국기술교육대학교 전기.전자.통신공학부) ;
  • 김기은 (한국기술교육대학교 전기.전자.통신공학부) ;
  • 홍송은 (한국기술교육대학교 전기.전자.통신공학부) ;
  • 박종운 (한국기술교육대학교 전기.전자.통신공학부)
  • Received : 2022.05.12
  • Accepted : 2022.06.22
  • Published : 2022.06.30
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Abstract

By an aid of needle coating, we have fabricated a spherical microlens array using poly(methyl methacrylate) for potential applications in light extraction of organic light-emitting diodes. With an attempt to achieve high-density and high-aspect-ratio microlens arrays, we have investigated the coating behaviors by varying the material parameters such as the solute concentration and wettability of the poly(methyl methacrylate) solution and process parameters such as the dwell time of needle near the substrate, retract distance of needle from the substrate, and coating gap between the needle and substrate. Under the optimized coating conditions, it is demonstrated that high-aspect-ratio microlens arrays can be obtained using a coating solution with high solute concentration and a small amount of a hydrophobic solvent. It is found that the diameter and height of microlens array are decreased with increasing poly(methyl methacrylate) concentration, yet the overall aspect ratio is rather enhanced. By the addition of 5 wt% hexylamine in 35 wt% poly(methyl methacrylate) solution, we have achieved a spherical microlens with the height of 7.7 ㎛ and the width of 94.24 ㎛ (the aspect ratio of 0.082). To estimate the capability of light extraction by the microlens array, we have performed ray tracing simulations and demonstrated that the light extraction efficiency of organic light-emitting diode is expected to be enhanced up to 24%.

Keywords

Acknowledgement

본 과제(결과물)는 2022년도 교육부의 재원으로 한국연구재단의 지원을 받아 수행된 지자체-대학 협력기반 지역혁신 사업의 결과입니다(2021RIS-004).

References

  1. Edward. W., Sang-Hyun. E., Weiran. C., "Enhancing Light Extraction in Top-Emitting Organic Light-Emitting Devices Using Molded Transparent Polymer Microlens Arrays", J. of Small, Vol. 8, pp. 2647-2651, 2012. https://doi.org/10.1002/smll.201102662
  2. Shogenji, R., Kitamura, Y., Yamada, K., Miyatake, S., Tanida, J., "Bimodal fingerprint capturing system based on compound-eye imaging module", Appl. Opt. 43, pp. 1355-1359, 2004. https://doi.org/10.1364/AO.43.001355
  3. Tian, Z., Wang, L., Chen, Q., Jiang, T., Qin, L., Wang, L., Sun, H., "Beam shaping of edge-emitting diode lasers using a single double-axial hyperboloidal micro- lens", Opt. Lett, Vol. 38, pp. 5414-5417, 2013. https://doi.org/10.1364/OL.38.005414
  4. Wu, M. H., and Whitesides, G. M., "Fabrication of diffractive and microoptical elements using microlens projection lithography", Adv. Mater, Vol. 14, pp. 1502-1506, 2002. https://doi.org/10.1002/1521-4095(20021016)14:20<1502::AID-ADMA1502>3.0.CO;2-M
  5. Jiun-Haw, L., Yu-Hsuan, H., Kuan-Yu, C., Hoang-Yan, L., Jheng-Hao, F., Sheng-Chih, H., Jia-Rong, L., Mao-Kuo, W., "Efficiency improvement and image quality of organic light-emitting display by attaching cylindrical microlens arrays", Opt. Exp, Vol. 16, pp. 21184-21190, 2008. https://doi.org/10.1364/OE.16.021184
  6. Cheong-Tang, P., Chi-Hui, C., Chi-Chang, H., "Technique of microball lens formation for efficient optical coupling", Appl. Opt. 43, pp 5939-5946, 2004. https://doi.org/10.1364/AO.43.005939
  7. Zoran. D., Robert. A., Neville Connell. G. A., "Technique for monolithic fabrication of microlens arrays", Appl. Opt, Vol. 27, pp. 1281-1284, 1988. https://doi.org/10.1364/AO.27.001281
  8. Feidhlim, T., Alun, J., Stephen, M., Michael, R., John, V., Justin, R., John, T., "Refractive elements produced in photopolymer layers", J. of Materials science, Vol. 40, pp. 4129-4132, 2005. https://doi.org/10.1007/s10853-005-2567-6
  9. Kyungjun, J., Jinyoung, L., Jongwoon, P., "Fabrication of Solution-Based Cylindrical Microlens with High Aspect Ratio", J. of the Semiconductor & Display Technology, Vol. 20, pp. 70-76 2021.
  10. June-Buem, P., Dong-Kyun, S., Seun-Gjo, H., Jong-Woon, P., "Enhancement of Light Extraction from Transparent OLED", J. of the Semiconductor & Display Technology, Vol. 16, pp. 41-45, 2017.