Transparent Conducting Electrode Interface Layer for Surface Smoothing

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Solution Overview

Problem

Transparent conducting electrodes with rough surfaces and pinholes in devices like OLEDs and electrochromic devices lead to localized short circuits and reduced performance, causing aesthetic issues and performance degradation.

Innovation Solution

Incorporating a thin interface layer, such as TiO2, SiO2, or ZnO, between the TCO and the active region of the device, which is deposited using techniques like CVD or sputtering, to smooth the surface and enhance the receptivity to subsequent layer deposition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a TCO layer is used as the uppermost layer of the transparent conducting electrode, then electrical properties and mechanical stability are improved, but surface roughness increases causing localized short circuits and performance degradation

Engineering Contradiction:

Improveelectrical stabilityVSAvoidsurface roughness

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

An interface layer comprising TiO2, SiO2, SnO2, ZnO or mixtures thereof is introduced between the TCO layer and the active region of the device. This intermediary layer smooths the inherently rough TCO surface, preventing localized short circuits while maintaining the electrical stability provided by the TCO layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The transparent conducting electrode is structured as a composite stack comprising a substrate, underlayers, a TCO layer, and an interface layer. This composite structure combines the electrical conductivity of TCO with the surface-smoothing properties of the interface layer materials, resolving the contradiction between electrical performance and surface quality.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If the TCO surface is inherently rough, then deposition of further layers is facilitated, but localized short circuits occur drawing current from areas up to a few millimeters from the short circuit point

Engineering Contradiction:

Improvelayer depositionVSAvoidlocalized short circuits

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The interface layer serves as a mediator between the rough TCO surface and the active region. It provides a smooth deposition surface for subsequent layers while preventing the harmful effect of localized short circuits that would otherwise occur on the rough TCO surface.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The interface layer converts the harmful surface roughness of the TCO into a beneficial feature by providing a controlled, smooth surface for layer deposition while eliminating the harmful localized short circuits. The roughness that would cause defects is transformed into a structured interface that enhances device performance.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Productivity

If pinholes are present in devices deposited on the TCO, then manufacturing is simplified, but similar problems of localized short circuits and performance reduction occur

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoiddevice performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The interface layer is deposited beforehand to cushion against the formation of pinholes and localized short circuits. By providing a continuous, smooth barrier layer prior to depositing the active region, it prevents defects from propagating through the device structure.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The interface layer acts as an intermediary barrier that prevents pinhole formation in the TCO layer from affecting the active region. This mediator layer maintains device reliability without compromising manufacturing efficiency, as it can be deposited using the same CVD process.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The interface layer significantly reduces roughness-related issues, improving device performance by maintaining electrical stability and facilitating smooth deposition of subsequent layers, resulting in enhanced light transmission and operational efficiency.

Implementation Method 1

Incorporating a thin interface layer between the top of the electrode stack (TCO) and the active region of the device overcomes problems associated with roughness of the TCO

Methodology Applied

Scientific EffectSurface smoothing:

Implementation Method 2

The good device performance obtained when such interface layers are included is surprising because these materials have high electrical resistance

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Implementation Method 3

Materials such as TiO2 and ZnO are is rendered more hydrophilic upon exposure to ultraviolet (UV) radiation. Such treatment of interface layers according to the invention renders the electrode more receptive to deposition of subsequent layers

Methodology Applied

Scientific EffectHydrophilicity enhancement:

Data Source

PatentUS9716243B2Interface layer for electronic devices

Publication Date: 2017.07.25 PILKINGTON GRP LTD

AI summary

Transparent conducting electrodes incorporate an interface layer located on the transparent conducting oxide (TCO) layer of the electrode. The interface layer offers a suitable surface for deposition of further layers in order to fabricate electronic devices such as electrochromic devices or organic light emitting diodes. Problems such as pinholes and short circuiting, associated with the inherent roughness of the TCO layer, are reduced.