**1. Introduction**

Today, using electronics is so much a part of our daily lives that we rarely imagine what life will be like without them. Electronics and mechanical assets are used in a variety of operations ranging from food to music. Because of the high demand for electrons, chemists, physicists, and other scientists and engineers are developing a plethora of novel organic materials that will change how society views technology [1]. Organic printed electronics are being developed for a variety of applications such as organic light-emitting diodes (OLEDs), organic photovoltaic cells (OPVs), electronic journals, portable electronics, and various sensors [2]. It is anticipated that compact, small, and lightweight devices with cost-effective usability can lead creativity into our lives, making research and development (R&D) in this field highly ambitious and universal [3].

OLEDs, as self-emitting devices, have high image efficiency, are ultra-thin, and light in weight [4]. They have become popular with the general public due to their use in mobile phones such as Samsung's Galaxy, iPhone, etc.**.** For the time being, OLEDs are mass-produced using an evaporation technique. While this method is

feasible for mass manufacture of small-scale to medium-sized OLED displays, but it is still thought that certain technological and cost challenges remain in the manufacturing of large TV displays. The main feature and efficiency of the OLED device depend on the types of materials used for fabrication.

The research of nanomaterials has recently gained increased interest due to their optical, mechanical, electrical, and chemical properties. Metals, semiconductors, carbon, and polymers are among the materials used to create nanoparticles, nanowires, nanotubes, and nanocomposites. These materials' uses cover optical and electronic instruments, as well as chemical and biomedical areas. Over the last century and a half, new groups of advanced materials known as polymers have been developed and researched, not only challenging the old classical materials but also enabling the creation of new goods that have led to the expansion of mankind's range of activities. Polymers are the foundation of many significant industrial products. Aside from social influences, their exponential rise in production is driven by the need to substitute conventional products. G. J. Berzelius, a Swedish chemist, invented the expression "polymer." He found benzene (C6H6) to be an ethyne polymer (C2H2). Later, this term underwent a minor change. The concept of polymers is one of the twentieth century's great ideas. It first appeared in the 1920s after much debate, and its acceptance is closely linked with the name of H. Staudinger, who won the Nobel Prize in 1953.

Thus, this chapter intended to describe and discuss the polymers used in OLEDs. Types of conducting polymer used and their synthesis process. Moreover, OLEDs mechanism and their structure. How the emissive layer affects OLEDs and their efficiency are reported. Also, types of OLEDs are used in this era and their benefits in day-to-day life.

### **2. Organic light emitting diode**

OLEDs (organic light-emitting diodes) are innovative developments in the field of optoelectrical systems for modeling next-generation versatile displays and devices that use organic thin film as an electroluminescent diode sensitive to current. There are different types of OLEDs classified below according to their light luminescence properties.

#### **2.1 Types of OLED**

There are several types of OLEDs which are used for a different purpose in day to day life. These are classified as, passive matrix, active matrix, transparent, topemitting, bottom emitting, foldable, white, and phosphorescent OLEDs as shown in **Figure 1** [1].

#### *2.1.1 Passive-matrix OLED (PMOLED)*

PMOLEDs include a cathode, organic layers, and anode. The anode and cathode are arranged in the way they are parallel to each other. Light is emitted by the pixel due to the intersections of the cathode and anode. External applied voltage helpful for the specific anode and cathode strips, for specifying which pixels light up and which stay dark. Once again, the light of each pixel is equal to the amount of current added. PMOLEDs are simple to produce, but they use more power than other forms of OLEDs, owing primarily to the power necessary for the external circuitry. PMOLEDs are ideally suited for small displays and are most useful for text and icons.

**5**

manufacturers.

as larger displays.

*Conducting Polymer-Based Emissive Layer on Efficiency of OLEDs*

*DOI: http://dx.doi.org/10.5772/intechopen.98652*

*2.1.2 Active-matrix OLED (AMOLED)*

*Schematic diagram of different types of OLEDs [5–8].*

**Figure 1.**

perfect applications for AMOLEDs.

*2.1.3 Transparent OLED (TOLED)*

*2.1.4 Top-emitting OLED (TEOLED)*

*2.1.5 Bottom-emitting OLED (BEOLED)*

AMOLEDs include complete layers of a cathode, organic molecules, and anode,

but the anode layer is overlaid by a matrix of thin-film transistors (TFTs). The circuitry that decides which pixels are switched on to form an image is the TFT array itself. Since the TFT array consumes less power than other alien electronics. AMOLEDs absorb less power than PMOLEDs, making them ideal for large displays. AMOLEDs also have higher refresh times, making them perfect for the film. Computer displays, large-screen TVs, and electronic signage or billboards are the

Transparent OLEDs contain translucent components (substrate, cathode, and anode) only, and can be up to 85% transparent when switched off from their substrate. The light will continue in both directions when a clear OLED monitor is enabled. Transparent OLED displays may be either active- or passive-matrix

The substrates of such OLEDs may be opaque or translucent. Since they are conveniently combined with a non-transparent transistor backplane, they are favored for active-matrix applications. Top-emitting OLED used in smart cards by

In this type of OLED organic materials are used. BEOLED contains transparent glass, TFT, ITO, an emission layer, and a cathode. Light emits from the bottom of the devices. Manufacture use bottom emitting OLED in smaller as well

displays. This machine can be used for heads-up displays.

*Conducting Polymer-Based Emissive Layer on Efficiency of OLEDs DOI: http://dx.doi.org/10.5772/intechopen.98652*

**Figure 1.**

*Light-Emitting Diodes and Photodetectors - Advances and Future Directions*

depend on the types of materials used for fabrication.

won the Nobel Prize in 1953.

**2. Organic light emitting diode**

*2.1.1 Passive-matrix OLED (PMOLED)*

luminescence properties.

**2.1 Types of OLED**

in **Figure 1** [1].

in day-to-day life.

feasible for mass manufacture of small-scale to medium-sized OLED displays, but it is still thought that certain technological and cost challenges remain in the manufacturing of large TV displays. The main feature and efficiency of the OLED device

The research of nanomaterials has recently gained increased interest due to their optical, mechanical, electrical, and chemical properties. Metals, semiconductors, carbon, and polymers are among the materials used to create nanoparticles, nanowires, nanotubes, and nanocomposites. These materials' uses cover optical and electronic instruments, as well as chemical and biomedical areas. Over the last century and a half, new groups of advanced materials known as polymers have been developed and researched, not only challenging the old classical materials but also enabling the creation of new goods that have led to the expansion of mankind's range of activities. Polymers are the foundation of many significant industrial products. Aside from social influences, their exponential rise in production is driven by the need to substitute conventional products. G. J. Berzelius, a Swedish chemist, invented the expression "polymer." He found benzene (C6H6) to be an ethyne polymer (C2H2). Later, this term underwent a minor change. The concept of polymers is one of the twentieth century's great ideas. It first appeared in the 1920s after much debate, and its acceptance is closely linked with the name of H. Staudinger, who

Thus, this chapter intended to describe and discuss the polymers used in OLEDs. Types of conducting polymer used and their synthesis process. Moreover, OLEDs mechanism and their structure. How the emissive layer affects OLEDs and their efficiency are reported. Also, types of OLEDs are used in this era and their benefits

OLEDs (organic light-emitting diodes) are innovative developments in the field of optoelectrical systems for modeling next-generation versatile displays and devices that use organic thin film as an electroluminescent diode sensitive to current. There are different types of OLEDs classified below according to their light

There are several types of OLEDs which are used for a different purpose in day to day life. These are classified as, passive matrix, active matrix, transparent, topemitting, bottom emitting, foldable, white, and phosphorescent OLEDs as shown

PMOLEDs include a cathode, organic layers, and anode. The anode and cathode are arranged in the way they are parallel to each other. Light is emitted by the pixel due to the intersections of the cathode and anode. External applied voltage helpful for the specific anode and cathode strips, for specifying which pixels light up and which stay dark. Once again, the light of each pixel is equal to the amount of current added. PMOLEDs are simple to produce, but they use more power than other forms of OLEDs, owing primarily to the power necessary for the external circuitry. PMOLEDs are ideally suited for small displays and are most useful for text and icons.

**4**

*Schematic diagram of different types of OLEDs [5–8].*

#### *2.1.2 Active-matrix OLED (AMOLED)*

AMOLEDs include complete layers of a cathode, organic molecules, and anode, but the anode layer is overlaid by a matrix of thin-film transistors (TFTs). The circuitry that decides which pixels are switched on to form an image is the TFT array itself. Since the TFT array consumes less power than other alien electronics. AMOLEDs absorb less power than PMOLEDs, making them ideal for large displays. AMOLEDs also have higher refresh times, making them perfect for the film. Computer displays, large-screen TVs, and electronic signage or billboards are the perfect applications for AMOLEDs.

#### *2.1.3 Transparent OLED (TOLED)*

Transparent OLEDs contain translucent components (substrate, cathode, and anode) only, and can be up to 85% transparent when switched off from their substrate. The light will continue in both directions when a clear OLED monitor is enabled. Transparent OLED displays may be either active- or passive-matrix displays. This machine can be used for heads-up displays.

### *2.1.4 Top-emitting OLED (TEOLED)*

The substrates of such OLEDs may be opaque or translucent. Since they are conveniently combined with a non-transparent transistor backplane, they are favored for active-matrix applications. Top-emitting OLED used in smart cards by manufacturers.

#### *2.1.5 Bottom-emitting OLED (BEOLED)*

In this type of OLED organic materials are used. BEOLED contains transparent glass, TFT, ITO, an emission layer, and a cathode. Light emits from the bottom of the devices. Manufacture use bottom emitting OLED in smaller as well as larger displays.

#### *2.1.6 Foldable OLED (FOLED)*

The substrates of FOLEDs are made of lightweight plastics or metallic foils. They have the benefits of being flexible, durable, and lightweight. Since the material is strong, corrosion and breakage are reduced, so it is used in GPS cameras, cellular phones, and big curved TVs. FOLEDs have many advantages, including higher image resolution and quicker response time. It has implementations in smartphones, GPS receivers, and OLED displays.

#### *2.1.7 White OLED (WOLED)*

White OLEDs provide the true color of incandescent lamps that produce brighter white light than fluorescent lights and bulbs that are standard and energization effective. They substitute fluorescent lamps which can reduce energy costs for lighting because they are manufactured in large sheets, are cost-effective, and use less electricity. It fits well for car lighting. White OLEDs are small and light, allowing automobiles to be more lightweight and powerful.

#### *2.1.8 Phosphorescent OLED (PHOLED)*

Heat production is minimized by using PHOLEDs. As a result, we will find it in a broad-sized OLED TV or lamps. PHOLEDs can significantly reduce temperature because they are energy-efficient. It also removes the amount of air conditioning needed to remove the heat produced and makes it a key component of a green or environment building strategy. PHOLEDs are used in computer displays, TV screens, and light tables.

#### **2.2 Structure and mechanism of OLEDs**

OLEDs operate similarly to traditional diodes and LEDs, but instead of using layers of n-type and p-type semiconductors to contain electrons and holes, they use organic molecules. Eight separate layers consist of an advanced OLED [8]. There are protective glass or acrylic layers on the top and bottom. The upper layer is the seal and the underlying substratum layer. There are a negative terminal and a positive terminal within these layers (called cathode and anode). Finally, two layers between the anode and cathode, the emissive layer (where light is produced). In between the emissive layer and anode, there are two layers to control and ejection of the hole called the hole injection layer and hole transport layer. Similarly, there also two layers in between the emissive layer and cathode called the electron transport layer and blocking layer [9]. **Figure 2** describes the structure and mechanism of OLEDs.

We simply connect a voltage (potential difference) between the anode and cathode to make an OLED light up. The cathode absorbs electrons from the power supply while the energy flows, while the anode loses them (or it "receives holes," if you prefer to look at it that way). An electron from the cathode moves towards the emissive layer through the electron transport layer. At the same time holes moves towards the emissive layer through-hole transport layer. The blocking layer and hole injection layer are used to control the electron and holes. At an emissive layer both electron and hole combined. As a hole (a lack of electron) collides with an electron, the two cancel each other out and emit a fleeting burst of energy in the form of a photon [9]. This is known as recombination, and since it occurs hundreds of times per second, the OLED emits constant light as long as the current flows. Overall, OLED goes through four fundamental steps [11],

**7**

**Figure 3.**

*Types of organic materials used for OLEDs [13].*

*Conducting Polymer-Based Emissive Layer on Efficiency of OLEDs*

i.Electron and hole injection at the electrodes.

*Schematic diagram of OLEDs and basic process of electroluminescence [10].*

iv.Radiative exciton decay and light emission.

**3. OLED materials**

**Figure 2.**

ii.Charge carriers are transported across the organic layers.

OLEDs are constantly developing and emphasizing the existence of customized functions of organic materials that can be added to well-preserved thin films. As a result, the materials' specifications are diverse, ranging from processability and

iii.The shape of electron–hole bound pairs (excitons).

*DOI: http://dx.doi.org/10.5772/intechopen.98652*

*Conducting Polymer-Based Emissive Layer on Efficiency of OLEDs DOI: http://dx.doi.org/10.5772/intechopen.98652*

#### **Figure 2.**

*Light-Emitting Diodes and Photodetectors - Advances and Future Directions*

allowing automobiles to be more lightweight and powerful.

The substrates of FOLEDs are made of lightweight plastics or metallic foils. They have the benefits of being flexible, durable, and lightweight. Since the material is strong, corrosion and breakage are reduced, so it is used in GPS cameras, cellular phones, and big curved TVs. FOLEDs have many advantages, including higher image resolution and quicker response time. It has implementations in smartphones,

White OLEDs provide the true color of incandescent lamps that produce brighter white light than fluorescent lights and bulbs that are standard and energization effective. They substitute fluorescent lamps which can reduce energy costs for lighting because they are manufactured in large sheets, are cost-effective, and use less electricity. It fits well for car lighting. White OLEDs are small and light,

Heat production is minimized by using PHOLEDs. As a result, we will find it in a broad-sized OLED TV or lamps. PHOLEDs can significantly reduce temperature because they are energy-efficient. It also removes the amount of air conditioning needed to remove the heat produced and makes it a key component of a green or environment building strategy. PHOLEDs are used in computer displays, TV

OLEDs operate similarly to traditional diodes and LEDs, but instead of using layers of n-type and p-type semiconductors to contain electrons and holes, they use organic molecules. Eight separate layers consist of an advanced OLED [8]. There are protective glass or acrylic layers on the top and bottom. The upper layer is the seal and the underlying substratum layer. There are a negative terminal and a positive terminal within these layers (called cathode and anode). Finally, two layers between the anode and cathode, the emissive layer (where light is produced). In between the emissive layer and anode, there are two layers to control and ejection of the hole called the hole injection layer and hole transport layer. Similarly, there also two layers in between the emissive layer and cathode called the electron transport layer and blocking layer [9]. **Figure 2** describes the

We simply connect a voltage (potential difference) between the anode and cathode to make an OLED light up. The cathode absorbs electrons from the power supply while the energy flows, while the anode loses them (or it "receives holes," if you prefer to look at it that way). An electron from the cathode moves towards the emissive layer through the electron transport layer. At the same time holes moves towards the emissive layer through-hole transport layer. The blocking layer and hole injection layer are used to control the electron and holes. At an emissive layer both electron and hole combined. As a hole (a lack of electron) collides with an electron, the two cancel each other out and emit a fleeting burst of energy in the form of a photon [9]. This is known as recombination, and since it occurs hundreds of times per second, the OLED emits constant light as long as the current flows. Overall,

*2.1.6 Foldable OLED (FOLED)*

GPS receivers, and OLED displays.

*2.1.8 Phosphorescent OLED (PHOLED)*

**2.2 Structure and mechanism of OLEDs**

structure and mechanism of OLEDs.

OLED goes through four fundamental steps [11],

screens, and light tables.

*2.1.7 White OLED (WOLED)*

**6**

*Schematic diagram of OLEDs and basic process of electroluminescence [10].*


iv.Radiative exciton decay and light emission.
