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Biodiversity Online J

Organic Light Emitting Diode (OLED) Technology and its Applications: Literature Review

Himadri Sekhar Das* and Prasanta Kumar Nandi

Department of Chemistry, Indian Institute of Engineering Science and Technology, Shibpur, Howrah, West Bengal, India

*Corresponding author: Himadri Sekhar Das, Department of Chemistry, Indian Institute of Engineering Science and Technology, Shibpur, Howrah, West Bengal, India

Submission: November 16, 2021; Published: December 07, 2021

ISSN 2637-7082
Volume2 Issue1

Abstract

An Organic Light Emitting Diode (OLED) was one of the growing leading semiconductor device technologies. This technology has several advantages over other technology such as eco-friendly lighting sources with superior color quality, wide viewing angle, mercury-free manufacture, fascinating flexibility etc. In an OLED a conducting an emissive layer was sandwiched between two electrodes to emits light in response to an electrical current. A various device structure, materials as well as deposition techniques have been investigated to achieve the better and improved performance of OLED. In this review we summarized the device architectures, materials and advantage and disadvantages of Organic Light Emitting Diode (OLED) has been discussed.

Keywords: Organic light emitting diode; Display; Liquid crystal display and organic LED; Hole transport layer; Hole block layer; Electron transport layer

Introduction

Organic Light-Emitting Diodes (OLEDs) have found applications in flat panel displays technologies suitable for information-display applications in the next generation of displays and solid-state lighting applications [1,2]. In Tang et al. [3] shows the performance of OLED as full-color display panels and eco-friendly lighting sources [3]. For a high-performance OLED device required a high opto-electrical property of Transparent Conducting Oxide (TCO) layer as an anode [4]. Development has been made through last few decades on luminance efficiency, color gamut, device stability, and fabrication techniques to achieve better performance of OLED [5-7]. Recent past OLEDs are used as indoor lighting and also in various display devices such as TV screens, pc monitor and transparent display in mobile phones, handheld game console, digital cameras, and ultra-high-definition televisions [8,9]. Still need some improvement the performance of OLED for competitive lighting sources and displays with desirable standards.

Design and working of device structures

Organic Light Emitting Diodes (OLEDs) are thin-film multi-layer device structure as shown in Figure 1a&b. Basically the structure consists of few layers like anode, Hole Injection Layer (HIL), Hole Transport Layer (HTL), Light-Emitting Layer (LEL), Electron Transport Layer (ETL), Electron Injection Layer (EIL) and cathode. Light was comes out when electrons and holes are injected into the light emitting layer from the two electrodes and recombined. The colour of the emitted light was depends on the emitter molecules. To obtain the high efficiency of the OLED design and optimization was one of the key factors.

Figure 1a: Working mechanism of OLEDs.


Figure 1b: Multilayer structure of Organic Light Emitting Diodes (OLEDs).


Fabrication Methods for OLEDS

In general, dry and wet process both are used to fabricate OLEDs. The commonly used dry process is vacuum evaporation. Also, OLEDs can be fabricated by the other process also like vacuum deposition or vacuum thermal evaporation, organic vapor phase deposition, inkjet printing, transfer-printing, lamination, spray coating and spin coating [10-15].
Based on the structure of OLEDs, they are classified into different types:
A. Passive OLED: In passive OLED the organic layer run perpendicularly between the strips of the anode and the cathode.
B. Active-matrix OLED: In case of active-matrix OLED an active component such as thin film transistor place on the top of the anode layer.
C. Transparent OLED: A transparent layer used as a substrate in this configuration with anode and cathode.
D. Top emitting OLED: The substrate layer in this OLED may be reflective/ non- reflective and the cathode layer is transparent.
E. White OLED: These types of OLEDs emit only white light and are used in the making of larger and efficient lighting systems.
F. Foldable OLED: Basically, such types of OLED made up of flexible metallic foil or plastic substrate.
G. Phosphorescent OLED: This OLED works on the principle of electroluminescence used to convert 100 % of the electrical energy into light (Table 1).

Table 1: Materials used for different layers in OLEDs [16,17].


Advantages

a) Low cost and manufacturing process of OLEDs leads itself several advantages over than TFT, LCD and plasma display.
b) OLED can fabricate on light weight and flexible plastic substrate.
c) Power efficiency of OLED better than other display technology.
d) OLEDs shows better response time rather than LCD.

Disadvantages

A. Power consumption was high compared to LCD.

B. Outdoor performance of OLEDs less reflective than LCD. C. In case of OLED display image can persistent cause a discrepancy due to lifespan of the organic dyes.
D. UV light exposure can be damaged OLEDs.
E. Water environment can easily damage OLEDs.

Conclusion

High contrast ratio and fast response time makes OLED most promising technology than LCDs. Development of OLEDs makes it advanced technology application like dashboards and in flexible displays. Few years ago, OLEDs are suffering due to limited lifetime for display applications still need OLEDs to overcome such challenges like heavy production costs and sensitivity to water vapor also its emissive nature suffers due to direct sunlight.

References

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  2. Lee MT, Lin JS, Chu MT, Tseng MR (2008) Improvement in carrier transport and recombination of white phosphorescent organic light-emitting devices using a composite blue emitter. Appl Phys Lett 93(13): 133306.
  3. Tang CW, Van Slyke SA (1987) Organic electroluminescent diodes. Appl Phys Lett 51(12): 913.
  4. Das HS, Das R, Nandi PK, Biring S, Maity SK (2021) Infuence of Ga-doped transparent conducting ZnO thin film for efficiency enhancement in organic light-emitting diode applications. Appl Phys A 127: 225.
  5. Schwartz G, Reineke S, Rosenow TC, Walzer K, Leo K (2009) Triplet harvesting in hybrid white organic light-emitting diodes. Adv Funct Mater 19(9): 1319-1333.
  6. Lee J, Chen HF, Batagoda T, Coburn C, Djurovich PI, et al. (2016) Deep blue phosphorescent organic light-emitting diodes with very high brightness and efficiency. Nature Mater 15(1): 92-98.
  7. Kuei CY, Tsai WL, Tong B, Jiao M, Lee WK, et al. (2016) Sky-blue organic light emitting diode with 37% external quantum efficiency using thermally activated delayed fluorescence from spiro-acridine-triazine hybrid. Advanced Materials 28(32): 6976-6983.
  8. Hung LS, Chen CH (2002) Recent progress of molecular organic electroluminescent materials and devices. Materials Science and Engineering R Reports 39(5-6):143-222.
  9. Lee C, Kim JJ (2013) Enhanced light out-coupling of OLEDs with low haze by inserting randomly dispersed nanopillar arrays formed by lateral phase separation of polymer blends. Small 9(22): 3858-3863.
  10. Dong SC, Xu L, Tang CW (2017) Chemical degradation mechanism of TAPC as hole transport layer in blue phosphorescent OLED. Organic Electronics 42: 379-386.
  11. Yang X, Wang R, Fan C, Li G, Xiong Z, et al. (2014) Ethoxylated polyethylenimine as an efficient electron injection layer for conventional and inverted polymer light emitting diodes. Organic Electronics 15(10): 2387-2394.
  12. Karzazi Y (2014) Organic Light Emitting Diodes: Devices and applications. Environ Sci 5(1): 1-12.
  13. Kim HH, Park S, Yi Y, Ick Son D, Park C, et al. (2015) Inverted quantum dot light emitting diodes using polyethylenimine ethoxylated modified ZnO. Sci Rep 5(1): 8968.
  14. Choi S, Zhou Y, Haske W, Shim JW, Fuentes Hernandez C et al. (2015) ITO-free large-area flexible organic solar cells with an embedded metal grid. Org Electron Physics Mater Appl 17: 349-354.
  15. Falco A, Zaidi AM, Lugli P, Abdellah A (2015) Spray deposition of Polyethylenimine thin films for the fabrication of fully sprayed organic photodiodes. Org Electron Physics Mater Appl 23: 186-192.
  16. Das HS, Biring S, Nandi PK, Das R (2021) Study the effect of Zno/Cu/Zno multilayer structure by rf magnetron sputtering for flexible display applications. Applied Physics A 127: 225.
  17. Das HS, Biring S, Nandi PK, Das R (2018) Comparative studies on the properties of magnetron sputtered transparent conductive oxide thin films for the application in solar cell. Applied Phys A p. 124.

© 2021 Himadri Sekhar Das. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and build upon your work non-commercially.

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