Organic Photoelectric Conversion Layer With Hole Blocking Layer
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Solution Overview
Problem
Existing imaging apparatuses using organic semiconductor materials face challenges in achieving spectral sensitivity in the near-infrared light region while minimizing dark current, as the band gap of these materials needs to be narrowed for longer absorption wavelengths, leading to increased dark current due to charge injection and generation within the photoelectric conversion layer.
Innovation Solution
The imaging apparatus incorporates a photoelectric conversion layer with a donor organic semiconductor material and an acceptor organic semiconductor material, along with a first blocking layer having an electron affinity lower than the acceptor organic semiconductor material, to control ionization potential and electron affinity, thereby enhancing spectral sensitivity in the near-infrared region and reducing dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the band gap of organic semiconductor materials is narrowed to achieve longer absorption wavelengths for near-infrared sensitivity, then spectral sensitivity in the near-infrared region is improved, but dark current increases due to charge injection and generation within the photoelectric conversion layer
Solution Approach 1:
A hole blocking layer is introduced as an intermediary between the photoelectric conversion layer and the electrode. This layer has an ionization potential higher than the donor organic semiconductor material, creating an energy barrier that selectively blocks hole injection from the electrode while allowing electron transport. This mediator structure enables near-infrared sensitivity with reduced dark current by preventing harmful charge injection without compromising photoelectric conversion efficiency.
Solution Approach 2:
The ionization potential of the hole blocking layer is specifically designed to be higher than the donor organic semiconductor material in the photoelectric conversion layer. This parameter change creates an energy barrier that selectively blocks holes while maintaining electron transport. By adjusting the ionization potential parameter of the blocking layer material, the device achieves both near-infrared spectral sensitivity and suppressed dark current through controlled charge injection barriers.
2Device complexity
If existing organic semiconductor materials are used in photoelectric conversion layers, then device structure can be simplified, but spectral sensitivity in near-infrared region cannot be achieved with sufficient efficiency
Solution Approach 1:
The photoelectric conversion layer is constructed as a composite material system combining donor organic semiconductor materials and acceptor organic semiconductor materials. This composite structure enables tuning of the absorption spectrum to cover the near-infrared region while maintaining organic material processing advantages. The composite organic-organic system achieves near-infrared sensitivity without requiring complex inorganic semiconductor structures, preserving device simplicity while extending spectral response.
3Productivity
If the photoelectric conversion layer is designed for high near-infrared absorption, then external quantum efficiency increases, but charge generation within the layer increases dark current
Solution Approach 1:
The hole blocking layer is positioned specifically at the interface between the photoelectric conversion layer and the electrode, creating a localized quality change at this critical interface. This localized structure has different properties (higher ionization potential) than the bulk photoelectric conversion layer, forming a selective barrier only where charge injection occurs. This local modification suppresses dark current from charge generation at the interface while preserving the high absorption and quantum efficiency of the bulk photoelectric conversion layer.
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 allows for higher spectral sensitivity in the near-infrared light region with reduced dark current, achieving external quantum efficiency greater than or equal to 1% and improved photoelectric conversion efficiency by suppressing electron excitation at the interface between the photoelectric conversion layer and the blocking layer.
Implementation Method 1
a photoelectric conversion layer disposed between the first electrode and the second electrode, and including a donor organic semiconductor material and an acceptor organic semiconductor material... The imaging apparatus has spectral sensitivity in a near-infrared light region having wavelengths of greater than or equal to 650 nm and less than or equal to 3000 nm
Data Source
AI summary
An imaging apparatus includes a semiconductor substrate; a first electrode; a second electrode; a photoelectric conversion layer disposed between the first electrode and the second electrode, and including a donor organic semiconductor material and an acceptor organic semiconductor material; a charge accumulation node positioned within the semiconductor substrate and electrically connected to the second electrode; and a first blocking layer disposed between the first electrode and the photoelectric conversion layer. The photoelectric conversion layer has an ionization potential of lower than or equal to 5.3 eV. The first blocking layer has an electron affinity lower than an electron affinity of the acceptor organic semiconductor material included in the photoelectric conversion layer. The imaging apparatus has spectral sensitivity in a near-infrared light region having wavelengths of greater than or equal to 650 nm and less than or equal to 3000 nm.