AMOLED Cathode Connection Areas for IR Drop Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Large-sized high-resolution AMOLED displays face IR drop issues due to thin film thickness requirements, leading to non-uniform and unstable screen displays, particularly in mass production for sizes G8.5 and above, where conventional auxiliary electrode designs are costly and complex, and backboard designs with high resolution pixels per inch (PPI) are difficult to implement.
Innovation Solution
The design involves forming auxiliary source traces at the bottom of the pixel definition layer with electrical conductors having protruding portions that are higher than the electroluminescence layer and cathode, with steep sidewalls to allow natural breaking of the electroluminescent material, enabling two-dimensional, enlarged connection areas for cathodes and electrical conductors, thus improving the IR drop issue without occupying extra space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the cathode film thickness is made very thin to achieve high transparency for top emission and high resolution, then the transparency and resolution are improved, but the impedance increases leading to large IR drop
Solution Approach 1:
The invention transitions from point-like contact (0D) to line contact (1D) to area contact (2D) by designing the auxiliary electrode as a columnar structure extending through the PDL layer. This dimensional expansion creates enlarged connection areas between the cathode and auxiliary electrode, reducing impedance and IR drop while maintaining thin film thickness for high resolution and transparency.
Solution Approach 2:
The auxiliary electrode is nested within the pixel structure by forming it as a columnar protrusion that extends from the anode side through the PDL layer to the cathode side. This nested design integrates the auxiliary electrode into the existing pixel architecture without occupying additional lateral space, allowing high transparency and resolution while providing enhanced electrical connection areas to reduce IR drop.
2Reliability
If an auxiliary electrode is fabricated into an inverted trapezoidal spacer column to provide additional assistance to areas of large IP drop, then the display uniformity is improved, but the manufacturing cost and process complexity increase
Solution Approach 1:
The invention merges the auxiliary electrode formation process with the existing PDL layer fabrication process. The auxiliary electrode columns are formed simultaneously with the PDL openings using the same photolithography and etching processes, eliminating the need for separate auxiliary electrode fabrication steps. This integration reduces process complexity and manufacturing cost while maintaining display uniformity.
Solution Approach 2:
The PDL layer serves multiple functions: it defines the pixel pattern, creates openings for organic material deposition, and simultaneously forms the structural framework for the auxiliary electrode columns. This multi-functionality reduces the number of separate processes needed while achieving both high resolution and improved display uniformity through the auxiliary electrode.
3Reliability
If a contact via is added to the backboard of EL/IJP-OLED to implement auxiliary electrode, then the IR drop problem is addressed, but the circuit design and backboard layout become more difficult for high resolution displays
Solution Approach 1:
The invention eliminates the need for complex backboard vias by moving the auxiliary electrode connection to the front side of the display. The auxiliary electrode columns extend vertically through the PDL layer to contact the cathode directly, creating a simple vertical connection path that avoids complex lateral routing and via formation in the backboard, thereby simplifying circuit design for high resolution displays.
Solution Approach 2:
Instead of adding auxiliary electrode connections from the backboard side (traditional approach), the invention implements the auxiliary electrode from the front side, with columns extending upward to meet the cathode. This inverted approach simplifies the backboard design while achieving the same IR drop compensation function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively addresses the IR drop problem in AMOLED panels by enhancing the connection areas between cathodes and electrical conductors, ensuring uniform and stable display performance while increasing the light-emitting area without additional space, thus improving the design for high-resolution displays.
Implementation Method 1
the cathode material can be evaporated at the broken positions to achieve electrical connections to the sidewalls of the electrical conductors
Data Source
AI summary
The present invention provides a display including: a thin film transistor substrate including a plurality of thin film transistors; a planarization layer; a plurality of anodes and a plurality of auxiliary source traces; a pixel definition layer having a plurality of first openings respectively corresponding to and exposing a plurality of auxiliary source traces and a plurality of second openings respectively corresponding to and exposing a plurality of anodes; a plurality of electrical conductors filled in the plurality of first openings and on a portion of the pixel definition layer around the plurality of first openings, wherein the plurality of electrical conductors have a plurality of protruding portions higher than the pixel definition layer; an electroluminescent layer; and a plurality of cathodes electrically connected to sidewalls of the plurality of electrical conductors respectively.