Principal Engineer Samsung Display Giheung, Republic of Korea
The organic light-emitting diode (OLED) panels showed a significant color change in the solar radiation evaluation. After exposure to solar radiation, the luminance of some OLEDs was significantly decreased. In these OLEDs, the purity of electron transport layer (ETL) material was noticeably decreased after light exposure. It was determined that some gasses came out from the pixel-define layer (PDL) by measuring the thermal desorption spectroscopy (TDS). By these gasses, the degradation was accelerated in organic layers and cathode. When the solar radiation evaluation was done with putting the 420 nm cut-off filter on the panel, the color variation was absolutely disappeared. We paid attention to this result that the problem was solved by blocking a near-UV light. A new capping layer (CPL) material increasing the absorption of near-UV light was used. While the solar radiation evaluation was passed, they had very small process margin on evaporation of red and green interlayer. Moreover, color difference of white light was increased. When a near-UV light absorbing dye was inserted to the polarizer film, color change in the solar radiation evaluation absolutely disappeared. Finally, we could pass the solar radiation evaluation through this attempt and the OLED panels with this polarizer film applied to mass production.