In the field of organic light - emitting diode (OLED) display technology, apart from the highly - regarded AMOLED (Active - Matrix Organic Light - Emitting Diode), PMOLED (Passive - Matrix Organic Light - Emitting Diode) also holds a significant position. Despite facing challenges from emerging display technologies like AMOLED in the wave of technological development, its unique technical characteristics and application advantages enable it to play an irreplaceable role in specific areas. Next, let's delve into the mysteries of PMOLED display technology.

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I. Working Principle of PMOLED​

PMOLED adopts a passive - matrix driving method, and its core principle involves controlling the luminescence of pixels through the intersection of row and column electrodes. In a PMOLED screen, organic light - emitting materials are coated on a glass substrate to form an organic light - emitting layer. The electrodes of the screen are divided into horizontal row electrodes and vertical column electrodes. When a certain pixel needs to emit light, voltages are applied to the corresponding row and column electrodes, and the electric current passes through the organic materials, prompting the organic light - emitting layer of that pixel to emit light. However, since PMOLED lights up pixels row by row, only one row of pixels can be lit at the same time, and the entire screen needs to be scanned rapidly in a cycle to maintain image display. This contrasts sharply with the independent control of each pixel in AMOLED.

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II. Structural Composition of PMOLED​

Substrate: Similar to AMOLED, PMOLED typically uses a glass substrate as the basic support structure. The glass substrate can provide a stable and flat surface for subsequent material deposition and electrode fabrication, ensuring the stability of display performance.​

Electrode Layer: The electrode layer of PMOLED consists of row electrodes and column electrodes, usually made of transparent conductive materials such as indium tin oxide (ITO). The row and column electrodes are perpendicular to each other, and the intersection points correspond to the pixel positions on the screen. These electrodes are responsible for transmitting electric current and controlling the luminescence state of the pixels.​

Organic Light - Emitting Layer: The organic light - emitting layer is the key part for PMOLED to achieve luminescence. It includes multiple functional layers such as the hole - injection layer, hole - transport layer, light - emitting layer, electron - transport layer, and electron - injection layer. Different functional layers work together to ensure the effective recombination of electrons and holes in the light - emitting layer, generating light radiation.​

Encapsulation Layer: Since organic materials are sensitive to oxygen and moisture and are prone to oxidation and degradation, which can affect the service life, PMOLED needs to be protected by an encapsulation layer. Common encapsulation methods include glass cover encapsulation and thin - film encapsulation to isolate the organic materials from the external environment.

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III. Advantages and Limitations of PMOLED​

(I) Technical Advantages​

Lower Cost: The manufacturing process of PMOLED is relatively simple. Without the need for a complex TFT array manufacturing process, it reduces production steps and equipment investment, giving it a significant cost advantage in the production of small - to - medium - sized, low - resolution display products.​

Fast Response Speed: The inherent luminescence properties of organic materials endow PMOLED with fast response capabilities. It can quickly switch the bright and dark states of pixels, presenting clear and smooth effects even when displaying dynamic images.​

Simple Structure: Its passive - matrix driving structure makes the circuit design of PMOLED relatively straightforward, facilitating product development and production. It is an ideal choice for application scenarios with relatively low technical requirements and a focus on cost control.​

(II) Application Limitations​

Limited Resolution and Size: Constrained by the passive - matrix scanning method, PMOLED has bottlenecks in high - resolution and large - size displays. As the screen size increases and the resolution improves, the number of scanned rows increases, resulting in a shortened pixel lighting time and reduced luminous efficiency, which affects the display brightness and image quality.​

Higher Power Consumption: Since PMOLED needs to continuously scan each row of pixels during the display process, there is continuous power consumption even when displaying static images. Compared with AMOLED, it consumes more power when displaying the same content, which is not conducive to battery life.

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IV. Application Scenarios of PMOLED​

Consumer Electronics: In small wearable devices such as smart bracelets and smartwatches, PMOLED is often used to display simple information such as time, step count, and heart rate. Its fast response and low - cost characteristics can meet the basic display function requirements of these devices while controlling product costs. In addition, some small electronic dictionaries, calculators, and other devices also use PMOLED displays to provide clear character and graphic displays.​

Industrial Display: In the field of industrial control, PMOLED is suitable for displaying simple status indicators, parameter information, etc., such as the displays of instruments and meters, and the operation panels of industrial equipment. Its stable display performance and anti - interference ability enable it to work reliably in complex industrial environments.​

Medical Equipment: Some medical monitoring devices, such as small oximeters and blood pressure monitors, use PMOLED displays to show measurement data. The clear display effect and low cost make it an economical and practical display solution in medical equipment.

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V. Development Prospects of PMOLED​

Despite the competition from technologies like AMOLED, PMOLED is constantly seeking innovation and breakthroughs. On the one hand, by optimizing materials and manufacturing processes, it aims to improve luminous efficiency, reduce power consumption, and enhance performance in high - resolution and large - size displays. On the other hand, it explores integration with emerging technologies to expand application areas. For example, in some Internet of Things devices and smart home control panels where display performance requirements are not high but cost - sensitivity is a concern, PMOLED is expected to gain wider applications with its cost and structural advantages. In the future, PMOLED will continue to play an important role in specific niche markets, complementing other display technologies and jointly promoting the development of the display industry.​

As a mature and distinctive display technology, PMOLED occupies a place in the display field with its unique advantages. With the continuous development of technology, it will demonstrate more value in a wider range of fields, bringing diverse display experiences to users.