Current Status and Future Directions of Light Emitting Diode

Finally, it is necessary to address the most obvious problem that LEDs are facing at present. Of course, it is the cost, this is the very much common obstacle that stops one product going for the market. LEDs are an energy efficient way of generating light. This is true, but it is expensive to produce them. The cost of LED mainly includes two parts, which are the material itself and manufacturing. For example, modern LED bulbs often contain 4 to 6 chips. Hence, the cost is 4 to 6 times more than the traditional lights.

Therefore, to reduce cost, manufacturing LEDs with only one chip is essential for such companies. This means the integration of the system should be improved, especially for the OLEDs in the display screen area.

Besides, finding a new LED component to replace the expensive one is also an effective way as well. Luckily, the progress in LED driver design, manufacturing process and building of industrial standard increased the quality of all LEDs up to a high grade, and reducing production costs at the same time.

The LEDs production efficiency has improved a lot, and this trend will continue. We can expect that the LEDs be used in our daily life one day, with the cost keeps going down.

The world is entering the era of internet of tings (IoTs). The emerging of smart city will bring revolution to the way of illumination. The integration of LEDs with building materials, decoration materials and household products will be a new trend, changing the traditional lighting methods.

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The property of LEDs makes it more easy to connect to the electronics. This makes the innovation of lighting products full of imagination. For example, the interaction between light and architecture, light and art, light and space, light and people becomes more imaginative, and transcending the concepts and categories of traditional lighting.

One typical solution is the LEDs illumination network through Power over Ethernet (PoE). Through PoE operation, the LED lighting system becomes an information network. The user can control the lighting and temperature in the vicinity. The system has access to other building services (such as via a mobile phone) and enables managers to better measure, monitor and control other building systems, such as real-time heating and ventilation. Then, the managers are able to use this data for historical trend analysis to identify opportunities to improve energy efficiency and operational efficiency. Therefore, the market for applications driven by the trend of electronic lighting may create greater opportunities.

Organic light emitting diodes attracted more attention with the development of flexible electronics. The structure of one typical OLED is shown in Figure 2(a). Basically, organic molecules and polymers are used in the emissive layer and conductive layer [20]. This is the reason that allows LEDs to be built on flexible substrates. The design of lighting and digital display are totally revolutionized by this new technology. In the near future, people will see that a screen can be folded like a piece of paper, and material could be pasted on the wall and works as an OLED display. This technology is new, there are still some challenges that we need to overcome, like the emitters, the light extraction or the solution based materials.

For the emitters, there are many questions regarding the thermodynamics of OLED, the degradation of the emitter needs to be minimized as well. When the emitter released a photon, it could be trapped by the encapsulating materials or organic layers. So the goal is to improve the efficiency of light extraction of OLED. This means most of that light should go to the viewing angle. Solution based materials have some advantages in manufacturing. So, they are the ideal material in the production of OLEDs, these materials are often dissolved in all kinds of solvents, then they can be used for the manufacturing by spin coating, ink-jet printing, or some sort of other printing methods. However, solution-based materials we are using in OLED today are not absolutely soluble. So finding a solvent to put them in is very difficult.

By the effort the material scientists, there are some companies have already started using OLEDs in their products (see Figure 2(b)), and a few foldable phones which utilize OLED technology are already shown on the market in 2019, like Samsung and Huawei, etc. We can expect that we will see more applications in the near future, even though the costs of these OLEDs products are still high. Light Fidelity (Li-Fi) technology uses various visible light as signal emission sources to control the communication between the light and the terminal receiver through the controller.

The Li-Fi uses visible light between 400 THz (780nm) to 800 THz (375nm) as the carrier for data transmission and for illumination. And a micro-LED light bulb can transmit at more than 10 Gbps [22]. Figure 3 shows the whole work process of this technology. Li-Fi system can use indoor lighting equipment instead of the wireless LAN local area network base station to transmit signals, and its communication speed can reach tens of megabits to hundreds of megabits per second. The future transmission speed may exceed the optical fiber communication. The system is also very safe, and the information will not leak to the outside once covering the light with curtains, and using multiple computers will not affect the communication speed as well. Since radio wave communication is not used, hospitals and other departments sensitive to electromagnetic signals are quite suitable to use the system.

As semiconductors, LEDs can turn on and off up to a million times per second, enabling the diodes to send data quickly. Li-Fi requires the LEDs to have a large bandwidth [23]. A type of LED suitable for Li-Fi application is needed in the future. Besides, there are still some issues need to consider. For example, sending signal from the LED bulb to the photodiode on the mobile phone only solves half of the problem. How to send a signal back from the mobile phone to ensure the communication is still challenging. Another problem is the environmental interference because the ambient light sources sometimes work in the same spectral band. At this time, if the ambient light source is strong, it is very likely that Li-Fi will not operate properly.