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Company News >> Development of OLED Panels for LGD Vehicles to Advance into Double Stacking Structure 26th,Apr,2018

South Korean panel makers are accelerating the development of automotive OLED display structures and organic materials. Compared with smartphones and TVs, automotive panels require more stringent temperature and humidity environments and are sensitive to external vibrations. Therefore, the direction to improve the display of general characteristics focuses on the development of extended life and enhanced reliability. According to the Korean media Kinews 5/24 report, LG Display (LGD) and Samsung Display (SDC) have publicly determined the OLED display structure for vehicles.

OLEDs for automobiles have higher reliability requirements than smart phones and OLEDs for televisions. The vehicle's display screen must withstand high pressures and maintain stable performance at extreme cold temperatures of either minus 40 degrees Celsius or extreme high temperatures of 95 degrees Celsius. Reliability test conditions: Normal temperature for more than 2000 hours under conditions of 40 degrees and 95% of standard humidity. Brightness requirement: Because it needs to be clearly visible under strong sunlight, the general brightness requirement is 450-500 cd/m2, and the brightness under special conditions is 600-1000 cd/m2 or more.

At present, the two companies are continuing their research on OLED organic materials, and at the same time they have announced the definitive OLED organic material color layer structure for vehicles.

LGD is based on the WOLED structure as a tandem structure in the red, green and blue (RGB) structure used in existing small and medium sized OLEDs. That is, in the RGB structure, the light emitting layer (EML) is stacked in a two-layer structure. Red+Red, Green+Green, Blue+Blue, EML is stacked in two layers to double the lifetime and efficiency of the luminescent materials.

However, charge generation layers (CGLs) need to be added separately between the 1- and 2-layer EMLs. CGL distributes the voltage to the upper and lower layers to make the device emit light. Lithium-containing electron transport layer (ETL) N-type CGL and P dopant-containing charge transport layer P-type CGL. The role of these two layers is to allow electrons in the ETL to easily enter the holes in the HTL. The N-type CGL employs faster ETL than the existing electronic transmission.

In the double-layered structure, the elements emit light separately, and the CGL layer increases the photon emission of electrons and holes. This will double the lifetime and current efficiency of OLED organic components. In addition, since the two layers emit light together, it is possible to compensate for lack of quality such as brightness. LGD applied for a patent on the double layer stacking and CGL structure.

Cadillac luxury sedan concept car with OLED screen ESCALA (Source: Cadillac)

In contrast, the Samsung display uses the same single-layer RGB structure as the small and medium size OLED display used in existing smartphones to make automotive OLED displays. In order to improve the reliability of the components, it is planned to use organic materials that are more adaptable to environmental changes, such as temperature resistance and humidity resistance.

According to sources in the industry, LGD behind Samsung's display in the competition of small and medium sized OLEDs is more active in product development. At present, LGD is increasing its investment in various applications of OLEDs.