Semiconductor Photoelectrode Moth-Eye Light Trapping
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Solution Overview
Problem
The existing semiconductor photoelectrodes face inefficiencies in light energy conversion due to scattered transmitted light being absorbed in the bulk before reaching the semiconductor thin film, reducing the utilization of reflected light.
Innovation Solution
A semiconductor photoelectrode with a moth-eye structure on the substrate surface, a semiconductor thin film, a catalyst layer, and a reflection layer on the opposite surface is used, controlling light diffusivity in one direction and enhancing light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a reflection layer is provided on the back surface of the semiconductor thin film to reflect transmitted light, then light absorption is improved, but the transmitted light is scattered within the bulk and most light is absorbed in the bulk before reaching the semiconductor thin film again
Solution Approach 1:
The invention introduces a moth-eye structure on the front surface of the substrate, creating a gradient refractive index layer that controls light propagation in the vertical dimension. This prevents lateral scattering of transmitted light within the bulk, ensuring that reflected light from the back surface travels directly back through the semiconductor thin film rather than being lost to lateral absorption in the bulk material.
Solution Approach 2:
The moth-eye structure acts as an intermediary between the incident light and the semiconductor thin film, and also between the reflected light and the semiconductor thin film. This gradient refractive index structure mediates the light paths, preventing direct absorption in the bulk while maintaining efficient coupling with the semiconductor thin film for photoexcitation.
2Use of energy by moving object
If the semiconductor thin film thickness is increased to absorb more light, then light absorption efficiency is improved, but the cost and manufacturing complexity increase
Solution Approach 1:
The invention changes the optical parameters of the system by introducing the moth-eye structure with its gradient refractive index. This allows thin semiconductor films (50-200 nm) to achieve the same light absorption efficiency as much thicker films would provide without the moth-eye structure, by trapping and redirecting light multiple times through the thin film.
Solution Approach 2:
The invention creates a composite structure combining the substrate with the moth-eye gradient refractive index layer and the semiconductor thin film. This composite approach enables enhanced light absorption in the thin semiconductor film by utilizing the optical properties of the moth-eye structure to increase the effective optical path length without increasing the physical thickness of the semiconductor layer.
Data Source
AI summary
A semiconductor photoelectrode includes a conductive or insulating substrate having a moth-eye structure on a surface; a semiconductor thin film disposed on a surface having the moth-eye structure of the substrate; a catalyst layer disposed on the semiconductor thin film; and a reflection layer disposed on a surface opposite to the surface having the moth-eye structure of the substrate.