Toward Organic Light Emitting Diode Satisfying Simultaneously Highly Enhanced Light Extraction and Lowly Ambient Light Reflection

Abstract

to their fast response time, high color quality, wide viewing angle, high brightness, low power consumption, and high luminous efficiency. [1][2][3][4][5][6][7][8][9][10][11][12][13] Currently, OLEDs are expanding their market to the world and becoming a mainstream in the display market as a leading display technology for smartphones, large size televisions, tablets, and many other display devices. Despite their many advantages, there are still calls for improved light efficiency. Above all, OLEDs have the disadvantage in that the image quality is deteriorated by external light in a bright surrounding environment because external light reflected from the metal electrode in OLEDs acts as a visual noise. Therefore, OLEDs have issues related to inevitable light efficiency, resulting from a polarizer and a quarterwave plate used to prevent deterioration of image quality from internal and external light interference. Under these conditions, the intensity of randomly polarized light emitted from an OLED device is intrinsically decreased by more than 50% by the polarizer, which eventually reduces the optical efficiency of the OLED device. Thus, many methods have been proposed to solve this problem [14][15][16][17][18][19][20][21] and have focused on stacked antireflection coatings, [14][15][16] low-reflectance materials, [17,18] absorption layers, [19][20][21] surface plasmonic, and microlens arrays. [22][23][24][25][26][27][28][29][30] However, most of these approaches fail to simultaneously satisfy a highly enhanced light extraction of the emitting light and lowly ambient light reflection. Above all, such methods are limited for use in a very narrow emission spectrum band, either red, green, or blue. Indeed, it is challenging to meet the demand for emissions in all directions, including oblique emissions, in previous OLED platforms. Furthermore, recently, studies on polarization light emitting have raised expectations for improved light efficiency, especially circularly polarized light emitting, which is theoretically the most appropriate method to improve light efficiency. [31][32][33] However, the study of circularly polarized light emission has been limited to the development of light emitting materials, and thus, there are many limitations on practicality. It is also a challenging project that requires a lot of time.Herein, we suggest a film for enhancing optical efficiency (FEOE) that drastically improves the optical efficiency of OLED It is verified that an organic light-emitting display (OLED) device combined with an advanced optical film characterized by the optical combination of a pyramid-shaped structure coupled with light absorber simultaneously satisfies highly enhanced light extraction and lowly ambient light reflection as one of the long-awaited needs of OLED. Thus, it does not require a polarizer that reduces optical efficiency in the OLED device. The results of the optical calculation for the OLED device combined with the proposed film indicate that its optical efficiency has been remarkably improved ...