Organic Imaging Element Layer Structure for Full Depletion and Low kTC Noise
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Solution Overview
Problem
In imaging elements, the direct accumulation of electric charges in organic photoelectric converters leads to incomplete depletion, resulting in increased kTC noise and deteriorated image quality due to the difficulty in fully depleting the organic photoelectric converter.
Innovation Solution
Incorporating a second semiconductor layer with a carbon-containing compound or inorganic compound having a higher electron affinity or work function than the first electrode between the photoelectric conversion layer and the second electrode, facilitating rapid transfer of electric charges to the first semiconductor layer, which includes an n-type semiconductor material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If electric charges are directly accumulated in a floating diffusion layer from an organic photoelectric converter, then the structure is simple, but the organic photoelectric converter cannot be fully depleted, resulting in increased kTC noise and deteriorated image quality
Solution Approach 1:
An intermediate layer (second semiconductor layer) is introduced between the organic photoelectric converter and the floating diffusion layer. This intermediate layer acts as a mediator that enables full depletion of the organic photoelectric converter while facilitating efficient charge transfer, thereby resolving the contradiction between structural simplicity and image quality.
Solution Approach 2:
The charge accumulation path is segmented into multiple stages: the organic photoelectric converter generates charges, the intermediate layer collects and transfers them, and the floating diffusion layer accumulates them. This segmentation allows each layer to be optimized for its specific function, enabling full depletion of the converter while maintaining manageable structural complexity.
2Device complexity
If no intermediate layer is provided between the organic photoelectric converter and the second electrode, then the device structure is simpler, but electric charges are not rapidly transferred, resulting in increased kTC noise
Solution Approach 1:
The second semiconductor layer serves as an intermediary that accelerates charge transfer from the organic photoelectric converter to the floating diffusion layer. This intermediate layer provides a favorable energy level alignment and charge transport pathway, enabling rapid charge extraction and reducing kTC noise without significantly increasing device complexity.
3Adaptability or versatility
If the work function of the second electrode is not matched with the photoelectric conversion layer, then the electrode material selection is flexible, but electric charges are not rapidly transferred to the first semiconductor layer
Solution Approach 1:
The energy level parameters (work function/electron affinity) of the intermediate layer are specifically adjusted to create an optimal energy gradient. This parameter optimization ensures that the intermediate layer has higher electron affinity than the first electrode, creating a driving force for rapid charge transfer while maintaining flexibility in material selection.
Solution Approach 2:
The intermediate layer is designed with specific local properties (high electron affinity or work function) that are tailored for charge transfer functionality. This localized optimization of material properties at the critical interface enables efficient charge transfer without constraining the overall material selection flexibility of the device.
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 configuration improves image quality by reducing kTC noise and enhancing the transfer efficiency of electric charges, allowing for better image acquisition in imaging apparatuses.
Implementation Method 1
electric charges generated in the photoelectric conversion layer are rapidly transferred to the first semiconductor layer
Implementation Method 2
light in a green wavelength band is photoelectrically converted by an organic photoelectric conversion film
Data Source
AI summary
An imaging element according to an embodiment of the present disclosure includes: a first electrode including a plurality of electrodes; a second electrode opposed to the first electrode; a photoelectric conversion layer including an organic material provided between the first electrode and the second electrode; a first semiconductor layer provided between the first electrode and the photoelectric conversion layer, and including an n-type semiconductor material; and a second semiconductor layer provided between the second electrode and the photoelectric conversion layer, and including at least one of a carbon-containing compound having an electron affinity larger than a work function of the first electrode or an inorganic compound having a work function larger than the work function of the first electrode.