Silicone-Induced Microlithography of Small-Molecule Phosphorescent Emitters for High-Resolution Micro-OLEDs

Organic light-emitting diodes (OLEDs) have emerged as a leading display technology, known for their exceptional color purity, rapid response time, slim design, and expanded color gamut. In the group of OLED materials, small-molecule based phosphorescent OLEDs, referred to as host-dopant systems, are favored for their superior luminous efficiency. These materials efficiently capture both singlet and triplet excitons, resulting in enhanced quantum efficiency and prolonged operational lifespans. This heightened efficiency makes phosphorescent OLEDs a preferred choice for a wide range of applications, including microdisplays for augmented reality, virtual reality, and mainstream commercial displays.<br/>Patterning small-molecule-based phosphorescent materials conventionally rely on fine metal masks (FMM) for deposition-based techniques. Recent demonstrations have achieved resolutions up to 3,000 pixels per inch (ppi) for small-molecule OLED microdisplays using FMM. However, FMM-based approaches have inherent limitations, including shadow effects caused by factors such as vapor path, deposition angles, and mask thickness. Alternative methods like template-directed growth and inkjet printing have been explored, but they often exhibit issues related to resolution, pattern fidelity, and fabrication yield which necessitates the exploration of novel approaches to achieve high-resolution patterning.<br/>To address these challenges, there is growing interest in utilizing reactive ion etching (RIE)-based photolithography for high-resolution patterning. RIE-based photolithography shows promise in achieving precise patterning. Nevertheless, the intrinsic limitations of small-molecule phosphorescent materials, characterized by their poor physico-chemical durability, have hindered their compatibility with RIE-based photolithography. This incompatibility leads to pattern degradation and compromises luminous properties, impeding the realization of high-resolution OLED microdisplays.<br/>Herein, we designed a novel paradigm by incorporating silicone into phosphorescent small-molecule networks. This silicone-integrated phosphorescent organic light-emitting network (SI-phOLEN), in which silicone molecules are homogeneously crosslinked with small-molecule light-emitting materials, can effortlessly achieve ultrahigh-resolution patterns via the photolithography process without degradation of their exceptional phosphorescent emission efficiency. On the basis of the unique features of SI-phOLEN, we firstly demonstrate ultra-fine patterns of the SI-phOLEN (down to 1 um) and high-resolution full-color RGB OLEDs corresponding to 3,000 ppi (4 um x 5 um anisotropic pattern). Our SI-phOLEN represents a transformative step in the pursuit of high-resolution OLED microdisplays and promises both fine patterning and improved luminescence properties. It marks a significant advance in the field of display technology, offering the potential to maximize performance and resolution to unprecedented levels.