Functionalized Polymer Side Chains for PLED Lifetime and Voltage

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Solution Overview

Problem

Conventional single-layer polymer light-emitting diodes (PLEDs) face challenges with poor lifetime and high driving voltage, particularly for blue PLEDs, due to the use of long flexible side-chains that enhance solubility but do not contribute to opto-electronic performance and reduce the volume of active materials.

Innovation Solution

Incorporating opto-electronic functional side-chains bound to the polymer backbone through a spacer, which improves the performance of PLEDs by enhancing lifetime, reducing driving voltage, and maintaining excellent solubility, while also applying these compounds in OLEDs to achieve better processability and performance in both PLEDs and small molecules/oligomers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If long flexible side-chains are used to enhance solubility, then solubility is improved, but lifetime and driving voltage performance deteriorate

Engineering Contradiction:

ImprovesolubilityVSAvoidlifetime

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The side-chain is segmented into two functional parts: a spacer portion attached to the backbone that provides structural separation, and a functional group portion that contributes opto-electronic properties. This segmentation allows the side-chain to serve multiple functions simultaneously - maintaining solubility through the spacer while improving device performance through the functional group.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The side-chain is designed with multi-functionality, where the spacer provides solubility and structural separation, while the functional group contributes to charge transport, hole injection, electron injection, or emission properties. This multi-functional design eliminates the trade-off between solubility and device performance by making the side-chain contribute to both processing and opto-electronic functions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Ease of manufacture

If long flexible side-chains are used to enhance solubility, then solubility is improved, but driving voltage increases

Engineering Contradiction:

ImprovesolubilityVSAvoiddriving voltage

Core Design Contradiction:

Ease of manufactureVSUse of energy by stationary object

Solution Approach 1:

The side-chain is divided into a spacer that maintains solubility and a functional group that optimizes charge transport properties. The functional group is specifically designed to facilitate charge injection and transport, reducing the energy barrier and thus lowering driving voltage while maintaining the solubility benefits of the spacer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The functional group in the side-chain is selected to have specific electronic properties (HOMO/LUMO levels) that optimize charge transport efficiency. By changing the electronic parameters of the side-chain through functional group selection, the energy barrier for charge injection is reduced, leading to lower driving voltage while the spacer maintains solubility.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If functional groups are directly bonded to the backbone, then opto-electronic performance is improved, but solubility deteriorates

Engineering Contradiction:

Improveopto-electronic performanceVSAvoidsolubility

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The spacer acts as an intermediary between the backbone and the functional group. It provides a physical and electronic buffer that allows the functional group to contribute to opto-electronic performance while the spacer itself maintains the solubility of the polymer. The spacer mediates between the conflicting requirements of direct bonding for performance and long chains for solubility.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Ease of manufacture

If long flexible side-chains are used, then solubility is improved, but the volume of active materials is reduced

Engineering Contradiction:

ImprovesolubilityVSAvoidvolume of active materials

Core Design Contradiction:

Ease of manufactureVSVolume of stationary object

Solution Approach 1:

The side-chain is segmented so that the spacer provides the bulk volume for solubility while the functional group provides the active opto-electronic functionality. This segmentation ensures that the majority of the side-chain volume (the spacer) contributes to solubility without wasting material, while the functional group delivers the required performance in a compact form.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The functional group is selected to have high opto-electronic activity per unit volume, maximizing the contribution to device performance while minimizing the volume occupied. This allows the active material volume to be optimized for performance while the spacer provides solubility without significant volume penalty.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9246103B2Polymers and oligomers with functionalized side groups

Publication Date: 2016.01.26 MERCK PATENT GMBH

AI summary

The present invention relates inter alia to oligomers and/or polymers with functionalized side groups which are bound to the backbone of the polymer via spacer.