Quantum Dot Light-Emitting Element Stack for Hole Injection Alignment
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Solution Overview
Problem
The inconsistency in ionization potential between the anode and the light-emitting layer in existing configurations inhibits efficient hole injection into the light-emitting layer.
Innovation Solution
A light-emitting element with a hole transport layer comprising an n+-type semiconductor layer and a p+-type semiconductor layer adjacent to the n+-type semiconductor layer, and a p-type semiconductor layer adjacent to the p+-type semiconductor layer, which are stacked in a specific order to improve hole injection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional hole transport layer is used, then the structure is simple, but hole injection efficiency is poor due to ionization potential inconsistency
Solution Approach 1:
The hole transport layer is segmented into multiple sub-layers with different conductivity types (n-type, p-type, and intrinsic layers). Each layer has a specific function: the n-type layer facilitates hole injection from the anode, the p-type layer transports holes to the light-emitting layer, and the intrinsic layer provides energy level alignment. This segmentation resolves the ionization potential inconsistency problem by creating intermediate steps for hole transport, thereby improving hole injection efficiency without requiring a single complex material.
Solution Approach 2:
Different regions of the hole transport layer are assigned different material properties and conductivity types tailored to local requirements. The n-type region near the anode has high electron concentration for efficient hole injection, the p-type region near the light-emitting layer has high hole concentration for efficient hole transport, and the intrinsic region provides energy level matching. This local optimization of material properties resolves the ionization potential mismatch while maintaining overall structural simplicity.
2Reliability
If a single-layer hole transport layer is used, then the manufacturing process is simple, but the ionization potential cannot be consistently matched between anode and light-emitting layer
Solution Approach 1:
The hole transport layer is divided into multiple functional sub-layers (n-type, p-type, and intrinsic layers) that can be fabricated using standard sequential deposition techniques. Each layer is deposited independently with controlled thickness and composition, allowing precise tuning of ionization potentials at each interface. This segmentation enables reliable ionization potential matching while maintaining compatibility with existing manufacturing processes.
Solution Approach 2:
The invention changes multiple parameters of the hole transport layer including conductivity type (n-type, p-type, intrinsic), layer thickness, and material composition. By adjusting these parameters independently for each sub-layer, the ionization potential can be precisely controlled at each interface to ensure consistent energy level alignment from the anode through to the light-emitting layer, thereby improving reliability without significantly complicating manufacturing.
Data Source
AI summary
A light-emitting element according to the present disclosure includes an anode, a hole transport layer, and a light-emitting layer containing a quantum dot, and a cathode in this order, and the hole transport layer includes an n+-type semiconductor layer, and a p+-type semiconductor layer adjacent to the n+-type semiconductor layer and disposed closer to the light-emitting layer than the n+-type semiconductor layer.