Dual-Layer PDL Structure for OLED Inkjet Printing

The PDL is divided into two distinct layers: a lower hydrophobic layer and an upper hydrophilic layer. Each layer serves a specific function - the hydrophobic layer provides good contact with the organic light-emitting material, while the hydrophilic layer prevents material splashing and diffusion to adjacent regions. This segmentation resolves the contradiction by combining the advantages of both material types in a multi-layer structure.

The PDL combines two materials with opposite hydrophobicity characteristics - a hydrophobic material (such as photoresist) and a hydrophilic material (such as silicon oxide or silicon nitride). This composite structure leverages the hydrophobic material's affinity for organic compounds and the hydrophilic material's repellent properties to achieve both good contact and effective containment of the light-emitting material.

The PDL is segmented into two layers with different heights, creating a recessed region within the luminous area. The lower hydrophobic layer forms the base with proper contact, while the upper hydrophilic layer extends higher to create containment walls. This segmentation prevents the organic material from forming arched protrusions by providing a physical barrier and proper surface energy gradient.

Different regions of the PDL are given different heights and material properties. The center region (within the luminous area) has a recessed structure with lower height, while the peripheral regions have higher height forming containment walls. This local quality variation ensures smooth material distribution in the center while preventing overflow at the edges.

The PDL opening structure is made asymmetric in vertical height across different regions. The peripheral regions have higher PDL walls that extend beyond the luminous region boundaries, while the central region has lower height to allow proper material filling. This asymmetric height distribution enables the opening to effectively contain material within the luminous region while maintaining complete filling capability.

The hydrophilic upper layer is positioned in advance to create a repulsive barrier before the organic light-emitting material is deposited. This preliminary anti-action prevents the material from splashing outward by providing a hydrophilic surface that repels the hydrophobic organic material, counteracting the natural tendency to spread and contaminate adjacent regions.