Photoelectric Conversion Device Charge Blocking Layer

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional photoelectric conversion devices suffer from increased dark current and reduced signal-to-noise ratio due to high external voltage applied across the photoelectric conversion layer, leading to inefficiencies in light utilization and color separation in solid-state imaging devices.

Innovation Solution

Incorporating a pair of charge blocking layers with higher relative dielectric constants than the photoelectric conversion layer, specifically a hole blocking layer and an electron blocking layer, to reduce charge injection and maintain high external quantum efficiency without excessive voltage, along with a semiconductor substrate configuration for improved color separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a large external voltage is applied to the photoelectric conversion layer to increase external quantum efficiency, then the external quantum efficiency is improved, but the dark current increases and the signal-to-noise ratio deteriorates

Engineering Contradiction:

Improveexternal quantum efficiencyVSAvoiddark current

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

A charge blocking layer is introduced as an intermediary between the electrode and the photoelectric conversion layer. This layer mediates the interaction by blocking charge injection from the electrode while still allowing the electric field to enhance charge separation in the photoelectric conversion layer, thus improving external quantum efficiency without increasing dark current

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The relative dielectric constant of the charge blocking layer is specifically designed to be larger than that of the photoelectric conversion layer. This parameter change creates a favorable electric field distribution that enhances charge separation efficiency while suppressing dark current generation

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a color filter is used to transmit only specific wavelengths for color separation, then color separation is achieved, but light use efficiency is reduced due to loss of non-transmitted light

Engineering Contradiction:

Improvecolor separationVSAvoidlight use efficiency

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The mechanical/optical color filter system is replaced with an electronic color separation system using stacked photodiodes with different band gaps. This substitution eliminates optical losses from filtering while achieving color separation through selective photoelectric conversion in each layer

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Color separation is achieved by transitioning from a two-dimensional planar color filter arrangement to a three-dimensional stacked photodiode structure. Each photodiode layer is positioned at different depths to detect different wavelengths, enabling color separation without optical filtering losses

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Productivity

If the size of photodiode is reduced to achieve high integration, then pixel density is improved, but light guidance into photodiode becomes difficult

Engineering Contradiction:

Improvepixel densityVSAvoidlight guidance efficiency

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The photoelectric conversion structure uses composite materials with different band gaps (GaAs, AlGaAs, InGaAs) in stacked layers. This composite structure enables each layer to efficiently absorb specific wavelength ranges, improving light capture efficiency even in miniaturized pixels

Inventive Principle:

Principle #40Composite materials

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 solution effectively reduces dark current and enhances external quantum efficiency while maintaining sensitivity and spectral sensitivity sharpness, improving color separation and overall performance of the photoelectric conversion device.

Implementation Method 1

a photoelectric conversion layer disposed between the pair of electrodes... a layer capable of absorbing incident light having a specified wavelength and generating charges (electrons and holes) corresponding to the quantity of absorbed light

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Implementation Method 2

the first charge blocking layer has a relative dielectric constant larger than a relative dielectric constant of the photoelectric conversion layer... for reducing the injection of a charge into the photoelectric conversion layer

Methodology Applied

Scientific EffectDielectric barrier effect: Dielectric

Data Source

PatentUS7566943B2Photoelectric conversion device and solid-state imaging device

Publication Date: 2009.07.28 FUJIFILM CORP

AI summary

A photoelectric conversion device including a photoelectric conversion part including a pair of electrodes and a photoelectric conversion layer provided between the pair of electrodes, wherein the photoelectric conversion part further includes a first charge blocking layer for reducing an injection of a charge into the photoelectric conversion layer from one of the pair of electrodes when a voltage is applied between the pair of electrodes, the first charge blocking layer being provided between the one of the pair of electrodes and the photoelectric conversion layer; and the first charge blocking layer has a relative dielectric constant larger than a relative dielectric constant of the photoelectric conversion layer.