Organic Photoelectric Conversion Layer for High Mobility Image Sensors
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Solution Overview
Problem
Organic photodiodes have low photoelectric conversion efficiency and carrier mobility compared to inorganic photodiodes, primarily due to short exciton diffusion distances and high resistance, mobility, and low carrier density, limiting their sensitivity and performance in solid-state image pickup devices.
Innovation Solution
A laminated image pickup element structure using organic photoelectric conversion layers with specific organic semiconductor materials, such as benzothienobenzothiophene systems and fullerene derivatives, to enhance hole mobility and photoelectric conversion efficiency, allowing for higher absorption coefficients and improved carrier transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If organic photodiode structures (p-n junction, p-i-n junction, bulk-hetero structure, buffer layer structure) are used, then photoelectric conversion efficiency is enhanced, but carrier mobility and sensitivity remain low compared to inorganic photodiodes
Solution Approach 1:
The patent changes the molecular parameters of the organic semiconductor material by introducing specific structural features (benzothienobenzothiophene core with bipolar character) to simultaneously improve hole mobility and photoelectric conversion efficiency, overcoming the limitations of conventional organic photodiode structures
Solution Approach 2:
The patent employs composite material strategy by combining the bipolar organic semiconductor ( exhibiting both electron- and hole-transporting properties) with fullerene derivatives to create a bulk-hetero structure that achieves high photoelectric conversion efficiency and carrier mobility simultaneously
2Device complexity
If conventional organic semiconductor materials are used, then device structure can be simplified, but exciton diffusion distance is limited to 20 nm or less, reducing photoelectric conversion efficiency
Solution Approach 1:
The patent changes the material parameters by using organic semiconductors with high absorption coefficients and appropriate energy level alignments, enabling efficient exciton generation and charge separation without requiring complex multi-layer structures, thus achieving high photoelectric conversion efficiency with simplified device architecture
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 proposed solution significantly enhances photoelectric conversion efficiency and carrier mobility, leading to higher sensitivity and performance in solid-state image pickup devices by optimizing the organic photoelectric conversion layer composition and structure.
Implementation Method 1
An image pickup element using an organic material (organic photodiode) can photoelectrically convert only a specific color (wavelength band)
Implementation Method 2
the organic material having a high absorption coefficient as compared with the photodiode using the silicon system semiconductor material exists
Data Source
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AI summary
An image pickup element is constituted by laminating at least a first electrode, an organic photoelectric conversion layer, and a second electrode in order, and the organic photoelectric conversion layer includes a first organic semiconductor material having the following structural formula (1).