Light-absorbing Material with Segmented Radical Site for Charge Recombination
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Solution Overview
Problem
Dye-sensitized photoelectric conversion elements face disappointing performance due to charge recombination, where photoexcited electrons react with the photosensitizing dye or holes, preventing efficient charge separation and output.
Innovation Solution
A light-absorbing material with a structure represented by X-Y, where X is a light-absorbing site and Y is a radical site that becomes oxidized or reduced, acting as an electron acceptor or donor, promoting high-speed oxidation-reduction reactions and charge separation by binding with an electron or hole transport layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional ruthenium complex dye is used as the photosensitizing dye, then the dye can absorb visible light and inject electrons into the semiconductor electrode, but charge recombination occurs where photoexcited electrons react with the dye or holes, reducing photoelectric conversion efficiency
Solution Approach 1:
The invention divides the photosensitizing dye into two separate functional components: a light-absorbing unit (X) and an electron-donating unit (Y). This segmentation allows the light-absorbing unit to capture photons and generate excitons, while the electron-donating unit rapidly transfers electrons to the semiconductor electrode, minimizing charge recombination between electrons and the dye molecule.
Solution Approach 2:
The electron-donating unit (Y) acts as an intermediary between the light-absorbing unit (X) and the semiconductor electrode. It receives electrons from the excited light-absorbing unit and rapidly transfers them to the semiconductor electrode, facilitating efficient charge separation and reducing the likelihood of recombination between electrons and the dye.
2Area of stationary object
If a single-layer sensitizing dye is used on the semiconductor electrode, then the structure is simple, but the interface area between the dye and electrode is limited, restricting electron injection efficiency
Solution Approach 1:
The invention employs a porous titanium oxide electrode structure that provides an extremely large actual surface area (roughness factor of about 720 for an 8 μm thick electrode). This porous architecture allows the sensitizer to cover a vastly increased interface area, enabling more dye molecules to participate in light absorption and electron injection simultaneously.
Solution Approach 2:
The sensitizer is designed as a composite molecule combining a light-absorbing unit (X) and an electron-donating unit (Y) with specific functional groups (carboxyl, phosphonic acid, or sulfur-containing groups) that bind to the titanium oxide surface. This composite structure optimizes both light absorption and electron transfer to the porous electrode.
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 light-absorbing material enhances photoelectric conversion efficiency by reducing charge recombination and improving output characteristics, achieving superior performance compared to conventional ruthenium complexes.
Implementation Method 1
Absorption of visible light by this sensitizing dye is by means of charge transfer transition from a metal to a ligand
Implementation Method 2
Absorption of visible light by this sensitizing dye is by means of charge transfer transition from a metal to a ligand
Implementation Method 3
injection of electrons from the photosensitizing dye into the conduction band of titanium oxide occurs at extremely rapid speeds
Implementation Method 4
the resulting photoexcited electrons are injected into the semiconductor electrode, improving the photoelectric conversion efficiency
Implementation Method 5
The carboxyl groups of ligands in the photosensitizing dye coordinate directly to Ti ions on the surface of the titanium oxide electrode
Implementation Method 6
The carboxyl groups of ligands in the photosensitizing dye coordinate directly to Ti ions on the surface of the titanium oxide electrode
Implementation Method 7
This titanium oxide electrode has a porosity of about 50%, and a porous structure with an extremely large actual surface area
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
The present invention provides a light-absorbing material capable of providing high photoelectric conversion efficiency when applied to a photoelectric conversion element. The light-absorbing material of the present invention has a structure represented by Formula (1) below: X-Y (1) (wherein X represents a light-absorbing site, and Y represents a radical site that becomes a radical when in an oxidized state and/or when in a reduced state, and is capable of repeated oxidation-reduction).