Semiconductor Electrode with Oxynitride Protection Layer
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Solution Overview
Problem
Semiconductor materials used in water splitting reactions under sunlight suffer from low hydrogen generation efficiency due to limited absorption of visible light, and existing protection layers, such as aluminum oxide, create a high potential barrier that impairs water splitting performance.
Innovation Solution
A semiconductor electrode with a conductive substrate, a visible light-absorbing semiconductor layer, and a thinner oxynitride protection layer that allows visible light to pass through, reducing the potential barrier and preventing chemical oxidation, while maintaining water splitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection layer such as aluminum oxide is applied to prevent chemical oxidation, then the semiconductor layer is protected from water contact, but a high potential barrier is created that impairs water splitting performance
Solution Approach 1:
The patent changes the material parameter of the protection layer from conventional oxides (aluminum oxide) to oxynitrides. This material substitution fundamentally alters the electronic structure and potential barrier characteristics, enabling the protection layer to simultaneously provide oxidation protection and maintain efficient charge carrier transport for water splitting reactions.
Solution Approach 2:
The patent employs oxynitride compounds as protection layers, which represent a composite material approach combining characteristics of both oxides and nitrides. This composite material structure allows tuning of the potential barrier height and width to optimize both protective function and photocatalytic activity, resolving the contradiction between protection and reactivity.
2Reliability
If conventional semiconductor materials like TiO2 are used, then the material is stable and well-established, but the ratio of utilizable light to total sunlight is very low (about 4.7%)
Solution Approach 1:
The patent modifies the band gap parameter of the semiconductor material by transitioning from wide-bandgap materials like TiO2 to visible light-absorbing materials. This parameter change enables the material to utilize a broader spectrum of sunlight (increasing utilization from 4.7% to 28%), while the applied oxynitride protection layer maintains the stability needed for practical applications.
3Reliability
If the protection layer is made thicker to improve protection, then chemical oxidation resistance increases, but visible light absorption is reduced and charge separation efficiency is impaired
Solution Approach 1:
The patent optimizes the thickness parameter of the protection layer to a specific range that balances protective function and optical transparency. Additionally, the material composition parameter is changed to oxynitride, which inherently provides better protection per unit thickness compared to conventional oxides, allowing thinner layers to achieve the same protective effect while maintaining light transmission.
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 semiconductor electrode effectively absorbs visible light, reduces charge separation efficiency loss, and maintains high photocurrent values over time, enhancing hydrogen generation efficiency without impairing water splitting characteristics.
Implementation Method 1
a semiconductor layer which is provided on the conductive substrate, and absorbs visible light
Implementation Method 2
electron-hole pairs are generated in the semiconductor. Semiconductors can be applied to uses such as light emitting diodes (LEDs) and lasers which extract light generated in recombination of the electron-hole pairs; solar cells which spatially separate the pairs to extract photovoltaic power as electric energy
Implementation Method 3
the protection layer has a lower potential barrier than aluminum oxide, and thus, the semiconductor electrode can inhibit deterioration of a water splitting performance with elapse of use time
Data Source
AI summary
A semiconductor electrode according to the present disclosure includes a conductive substrate; a semiconductor layer which is provided on the conductive substrate, and absorbs visible light; and a protection layer with which the semiconductor layer is coated, in which the protection layer is formed of an oxynitride, the visible light travels through the protection layer, and the protection layer has a thinner thickness than the semiconductor layer.