Transparent P-Type Materials for Organic Photodiode Absorption Layers
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Solution Overview
Problem
Current organic image sensors face challenges with low photoelectric conversion efficiencies and high dark currents due to the materials used in their light-sensing units, which also reduce spatial resolution and light collection efficiency.
Innovation Solution
A transparent P material is introduced, capable of forming high-quality homogenous films and efficiently dissociating excitons in colored materials through HOMO dissociation, with specific absorption coefficients in the visible wavelength range, allowing for improved photoelectric conversion in organic image sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If organic materials are used in photoelectric conversion layers, then the device can be manufactured with organic materials, but photoelectric conversion efficiency is low and dark current is high
Solution Approach 1:
The patent uses composite materials by combining a transparent P-type organic material with colored N-type materials to form a bulk heterojunction. The transparent P-material (such as BDT-TT or BDT-TF derivatives) has low absorption coefficient in the visible range and high hole mobility, while the colored N-materials provide strong light absorption. This composite structure resolves the contradiction by maintaining ease of organic material manufacturing while achieving high photoelectric conversion efficiency through the synergistic combination of materials with complementary properties.
2Adaptability or versatility
If color filters are used to separate light by color, then different wavelengths can be detected, but spatial resolution and light collection efficiency are reduced
Solution Approach 1:
The patent applies local quality by creating a bulk heterojunction where different materials are distributed at the nanoscale throughout the photoelectric conversion layer. Instead of using macroscopic color filters that block light, the transparent P-material and colored N-material are mixed at the molecular level, allowing each material to perform its function locally: N-materials absorb specific wavelengths while P-materials transport holes. This eliminates the need for separate color filter layers, thereby maintaining spatial resolution while achieving wavelength-selective detection.
3Reliability
If a transparent P-material is used to decouple absorption from charge transport, then photoelectric conversion efficiency improves, but material design and synthesis become more complex
Solution Approach 1:
The patent segments the functional requirements of the photoelectric conversion layer by using distinct materials for different functions: the transparent P-material is specifically designed for charge transport (hole mobility > 10^-6 cm²/Vs) with minimal light absorption, while colored N-materials are optimized for light absorption. This functional segmentation allows each material to be optimized independently for its specific role, achieving high photoelectric conversion efficiency while managing design complexity through clear functional division rather than attempting to create a single material that performs all functions.
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 transparent P material enhances photoelectric conversion efficiency, reduces dark currents, and maintains high spatial resolution by decoupling absorption properties from electron/hole transfer and transport properties, leading to improved performance in organic image sensors.
Implementation Method 1
to dissociate efficiently the excitons created in colored N, or in a mixture of colored N materials (N1:N2), or in another colored P or in a mixture of colored P and N materials (P2:N) via a process of HOMO dissociation
Implementation Method 2
an absorption coefficient (in single material film) of less than 70,000 cm−1 for wavelengths longer than 450 nm, or an absorption coeffiecient (in single material film) of less than 40,000 cm−1 for wavelengths longer than 500 nm
Data Source
AI summary
The present disclosure relates to transparent P materials and their use in absorption layer(s), photoelectric conversion layer(s) and/or an organic image sensor and methods for their synthesis.