Photoelectric Conversion Element Dark Current Stabilization
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Solution Overview
Problem
Photoelectric conversion elements used as photodetectors experience variations in dark current due to applied voltage, affecting detection precision, and this variation is device-dependent, making it undesirable.
Innovation Solution
A photoelectric conversion element with a bulk heterojunction active layer containing a p-type semiconductor material with a band gap of 0.5 eV to 1.58 eV and an n-type semiconductor material, specifically C60 fullerene derivative, where the junction length between phases is adjusted to 120 μm to 170 μm per square micrometer, stabilizing the dark current across voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photoelectric conversion element is used as a photodetector with voltage applied, then light detection function is achieved, but dark current varies with applied voltage reducing detection precision
Solution Approach 1:
The invention changes the physical parameters of the active layer by controlling the band gap of the p-type semiconductor material (0.5 eV to 1.58 eV) and the junction length between phases (120 μm to 170 μm per square micrometer). These parameter changes optimize the dark current characteristics to reduce voltage-dependent variation while maintaining photodetection functionality.
Solution Approach 2:
The invention uses a composite bulk heterojunction active layer combining p-type semiconductor material and n-type semiconductor material (C60 fullerene derivative). This composite structure creates a phase separation morphology that stabilizes dark current across different applied voltages, resolving the contradiction between detection function and dark current stability.
2Measurement precision
If the dark current is reduced to improve detection precision, then measurement accuracy improves, but the photoelectric conversion efficiency may be affected
Solution Approach 1:
The invention optimizes the band gap parameter of the p-type semiconductor material within a specific range (0.5 eV to 1.58 eV) to achieve a balance between dark current suppression and photoelectric conversion efficiency. This parameter optimization allows the system to maintain both low dark current and high detection efficiency.
Solution Approach 2:
The invention creates local phase separation in the active layer with controlled junction length (120 μm to 170 μm per square micrometer). This local structural optimization ensures that charge generation and transport occur efficiently at the phase interfaces while maintaining low dark current in the bulk regions.
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 significantly reduces dark current variation with voltage, enhancing the precision and stability of light detection regardless of the applied voltage, making the photoelectric conversion element suitable for various applications.
Implementation Method 1
By the energy (hν) of light that enters the organic active layer, charges (holes and electrons) are generated in the organic active layer, the generated holes move toward the anode, and the electrons move toward the cathode.
Implementation Method 2
An active layer having a phase separation structure that is made by mixing an n-type semiconductor material (electron acceptor compound) and a p-type semiconductor material (electron donor compound) and comprises a phase containing the n-type semiconductor material and a phase containing the p-type semiconductor material
Data Source
AI summary
A photoelectric conversion element capable of reducing a specific dark current. In a photoelectric conversion element (10) including an anode (12), a cathode (16), and an active layer (14) provided between the anode and the cathode, the active layer contains a p-type semiconductor material having a band gap of 0.5 eV to 1.58 eV, and an n-type semiconductor material, the n-type semiconductor material is a C60 fullerene derivative, and on an image obtained by binarizing an image of the active layer observed by a transmission electron microscope, the junction length between a phase of the n-type semiconductor material and a phase of the p-type semiconductor material is 120 μm to 170 μm per square micrometer of the area of the binarized image.