Light Extraction Efficiency Enhancement of White Organic Light-Emitting Diodes (OLEDs) by Micro/Nano-Patterning the Substrate Layer

Abstract:

We demonstrate the enhancement of light extraction efficiency of surface-emitting white Organic Light Emitting Diodes (OLEDs) by incorporating micro/nano-metric structures on the outer surface of the 3-layer substrate (SiO₂-Si₃N₄-SiO₂). To enhance light extraction efficiency of the OLEDs, various light scattering structures including plano-convex & plano-concave micro-lens array, flat-top & round-top nano-pillars array, and wavy structures were engraved on the outer surface of the substrate layer. For optimization, we varied the thickness of the internal layers of the OLEDs, and height, width, period, and radius of the micro/nano-scale structures. The performance of the micro/nano-structured OLEDs was simulated and analyzed using Lumerical FDTD and GPVDM simulators. We examined the far field light intensity, transmitted power, angular distribution of light, photon escape probability, photon density, internal & external quantum efficiency, and current-voltage curve of the designed OLEDs. We investigated the results in different locations, especially after the substrate layer: Far Field-1 (0 μm), and Far Field-2 (2.5 μm). Compared to conventional OLEDs, the micro/nano-structured OLEDs showed higher external quantum efficiency. The highest external quantum efficiency of 67.304% (Far Field-1) was detected in the round-top nano-pillars array engraved white OLED having structure period of 1.2 μm. We strongly believe that, the proposed micro/nano-structured white OLEDs are suitable for lighting applications.

• Periodical: Defect and Diffusion Forum (Volume 432)
• Pages: 85-106
• DOI: https://doi.org/10.4028/p-BX2Ouv
• Online since: March 2024
• Authors: Md. Shamim Ahsan*, Md. Arif Istiaq Arafat, Tasmima Akter, Ik Bu Sohn, Hun Kook Choi
• Keywords: External Quantum Efficiency, Finite Difference Time Domain (FDTD), Light Extraction Efficiency, Micro/Nano-Patterning, Organic Light Emitting Diode

References

[1] H.J. Round, A note on carborundum, Electr. World 19 (1907) 309.

[2] J.I. Hwang, R. Hashimoto, S, Saito, S. Nunoue, Development of InGaN-based red LED grown on (0001) polar surface, Appl. Phys. Express 7 (2014) 071003.

DOI: 10.7567/apex.7.071003

[3] D.R. Opel, E. Hagstrom, A.K. Pace, K. Sisto, S.A.H. Ali, S. Desai, J. Swan, Light-emitting diodes: a brief review and clinical experience, J. Clin Aesthet Dermatol. 8 (2015) 36-44.

[4] P. Vashishtha, M. Ng, S.B. Shivarudraiah, J.E. Halpert, High efficiency blue and green light-emitting diodes using ruddlesden-popper inorganic mixed halide perovskites with butylammonium interlayers, Chem Mater. 31 (2019) 83-89.

DOI: 10.1021/acs.chemmater.8b02999

[5] M. Pope, H.P. Kallmann, P. Magnantem, Electroluminescence in organic materials, J. Chem. Phys. 38 (1963) 2042.

[6] C.W. Tang, S.A. Vanslyke, Organic electroluminescent diodes, Appl. Phys. Lett. 51 (1987) 913.

[7] G. Hong, X. Gan, C. Leonhardt, Z. Zhang, J. Seibert, J.M. Busch, S. Bräse, A brief history of OLEDs: emitter development and industry milestones, Adv. Matter. 33 (2021) 2005630.

DOI: 10.1002/adma.202005630

[8] O. Vyavahare, Fabrication and characterization of organic light emitting diodes for display applications, Thesis, Rochester Institute of Technology (2009).

[9] J.H. Kwon, R. Pode, High efficiency red phosphorescent organic light-emitting diodes with simple structure, S.H. Ko (Eds.), Organic Light Emitting Diode–Material, Process and Devices, IntechOpen, 2011.

DOI: 10.5772/18521

[10] J.H. Lee, C.H. Chen, P.H. Lee, H.Y. Lin, M.K. Leung, T.L. Chiu, C.F. Lin, Blue organic light-emitting diodes: current status, challenges, and future outlook, J. Mater. Chem. C 7 (2019) 5874-5888.

DOI: 10.1039/c9tc00204a

[11] B.W. D'Andrade, S.R. Forrest, White organic light-emitting devices for solid-state lighting, Adv. Mater. 16 (2004) 1585-1595.

DOI: 10.1002/adma.200400684

[12] A. Misra, P. Kumar, M.N. Kamalasanan, S. Chandra, White organic LEDs and their recent advancements, Semicond. Sci. Technol. (2006) R35-R47.

DOI: 10.1088/0268-1242/21/7/r01

[13] S.-H Cho, J.R. Oh, H.K. Park, H.K. Kim, Y.-H. Lee, J.-G. Lee, Y.R. Do, Highly efficient phosphor-converted white organic light-emitting diodes with moderate microcavity and light-recycling filters, Opt. Express 18 (2010) 1099-1104.

DOI: 10.1364/oe.18.001099

[14] Y.-L. Chang, Z.-H. Lu, White organic light-emitting diodes for solid-state lighting, J. Disp. Technol. 9 (2013) 459-468.

DOI: 10.1109/jdt.2013.2248698

[15] R. Pode, Organic light emitting diode devices: An energy efficient solid state lighting for applications, Renewable Sustainable Energy Rev. 133 (2020) 110043.

DOI: 10.1016/j.rser.2020.110043

[16] Q. Yue, W. Li, F. Kong, K. Li, Enhancing the out-coupling efficiency of organic light-emitting diodes using two-dimensional periodic nanostructures, Adv. Mater. Sci. Eng. 2012 (2012).

DOI: 10.1155/2012/985762

[17] J. Wang, W. Li, C. Wang, Improving light outcoupling efficiency for OLEDs with microlens array fabricated on transparent substrate, J. Nanomater. 2014 (2014).

DOI: 10.1155/2014/289752

[18] M.S. Ahsan, M.R. Hossain, S. Mehbuba, K.M. Sarif Islam, M.Z. Amin, I.-B. Sohn, Efficiency improvement of organic light emitting diodes (OLEDs) using micro/nano-structures, Proc. ICEEICT 2016, Dhaka Bangladesh (2016).

DOI: 10.1109/ceeict.2016.7873069

[19] A. Adhikary, M.S. Ahsan, M.M. Hossain, M.B. Hossain, S.H.S. Newaz, F. Ahmed, I.-B. Sohn, Improvement of light intensity and efficiency of n-ZnO/NiO/p-GaN heterojunction-based white light emitting diodes using micro-/nanolens array, Opt. Eng. 59 (2020) 117108.

DOI: 10.1117/1.oe.59.11.117108

[20] Y. Wang, M. Liu, J. Wang, Y. Zhang, Y. Qin, Y. Lu, Y. Chen, X. Zhang, W. Huang, Enhancing the light out-coupling efficiency of organic light-emitting devices with random corrugated structures, Thin Solid Films 732 (2021) 138791.

DOI: 10.1016/j.tsf.2021.138791

[21] T. Akter, A.I. Arafat, M.S. Ahsan, Efficiency enhancement of organic light emitting diodes (OLEDs) by micro/nano-structuring the substrate layer, Proc. ICECIT 2021 (2021).

DOI: 10.1109/icecit54077.2021.9641370

[22] D.-H Cho, J.-W Shin, C.W. Joo, J. Lee, S.K. Park, J. Moon, N.S. Cho, H. Y. Chu, J.-I. Lee, Light diffusing effects of nano and micro-structures on OLED with microcavity. Opt. Express 22 (2014) A1507.

DOI: 10.1364/oe.22.0a1507

[23] E.-J Bae, S.-W. Kang, G.-S. Choi, E.-B. Jang, D.-H Baek, B.-K Ju, Y.-W. Park, Enhanced light extraction from organic light-emitting diodes with micro-nano hybrid structure, Nanomater. 12 (2022) 1266.

DOI: 10.3390/nano12081266

[24] T. Akter, A.I. Arafat, Efficiency enhancement of organic light-emitting diodes (OLEDs) by micro/nano-structuring the substrate layer, Undergraduate Thesis, Khulna University, Bangladesh (2022).

DOI: 10.1109/icecit54077.2021.9641370