Translucent Support for Semiconductive Thin Film Structure
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Solution Overview
Problem
Existing light-trapping structures for laser-crystallized thin-film solar cells lack temperature stability and material quality, leading to suboptimal optical and electronic properties, and are not suitable for high-temperature liquid-phase crystallization processes.
Innovation Solution
A light-trapping structure with a homogeneous silicon oxide layer featuring a periodic nanostructure and a nanocrystalline titanium or tin oxide antireflection layer, which reduces the nanostructure height by at least 30% and includes a passivation layer, providing a smooth yet three-dimensionally textured surface for improved light scattering and anti-reflection properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If rough nanostructures are used for anti-reflection coating, then optical properties are significantly improved, but electronic properties of the solar cell deteriorate
Solution Approach 1:
The light-trapping structure is segmented into two distinct layers: a lower three-dimensional structure layer (height 50-200 nm) that provides optical scattering, and an upper flat antireflection layer (thickness 5-20 nm) that provides electronic passivation. This segmentation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
Different regions of the structure have different properties: the lower layer has three-dimensional nanostructures for light scattering, while the upper layer has a flat surface for electronic passivation. This local differentiation of properties resolves the contradiction between optical and electronic requirements.
2Reliability
If flat anti-reflection layers are used, then electronic properties are maintained, but optical properties deteriorate with poor anti-reflection performance
Solution Approach 1:
The structure separates optical and electronic functions into different layers: the lower three-dimensional layer handles light scattering while the upper flat layer provides electronic passivation, allowing both functions to coexist without compromise.
Solution Approach 2:
The solution transitions from a two-dimensional flat surface to a three-dimensional structured lower layer with a flat upper layer, adding vertical dimensionality to simultaneously achieve both optical scattering and electronic passivation.
3Ease of manufacture
If conventional materials are used in light-trapping structures, then manufacturing is easier, but temperature stability deteriorates for laser crystallization
Solution Approach 1:
The light-trapping structure uses a composite of silicon oxide (lower layer) and antireflection material (upper layer), both selected for their high temperature stability. This composite material approach maintains ease of manufacture through standard deposition techniques while achieving the required temperature stability for laser crystallization processes.
4Illumination intensity
If three-dimensional nanostructures are used, then light scattering increases, but material quality deteriorates due to interface structuring
Solution Approach 1:
The structure separates the scattering function (lower three-dimensional layer) from the material quality requirement (upper flat layer), allowing light scattering to occur at the lower interface while maintaining high material quality at the upper semiconductor interface.
Solution Approach 2:
Different regions have different structural qualities: the lower layer has three-dimensional structures for scattering, while the upper layer has a flat, high-quality surface. This local differentiation resolves the contradiction between scattering efficiency and material quality.
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
This structure enhances the material quality and optical properties of thin-film solar cells, increasing short-circuit current density and efficiency while maintaining temperature stability for liquid-phase crystallization processes.
Implementation Method 1
which cause scattering and increase the optical path length of the light in the absorber layer
Implementation Method 2
The introduction of additional layers at the glass-silicon interface makes it possible to reduce these reflection losses
Implementation Method 3
the silicon is heated locally and for a very limited period of time to above the melting point (approx. 1,400 °C), so that a phase transformation results in a rearrangement of large crystallites
Implementation Method 4
so that a phase transformation results in a rearrangement of large crystallites
Implementation Method 5
An approach to flatten random pyramids with a typical period of 2 μm and a typical height of 800 nm from glass-like hydrogen silsesquioxane (acronym HSQ) in superstrate a-Si solar cells is described in publication II
Data Source
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AI summary
Special light-trapping structures for increasing absorption are required for light-absorbing semiconductor thin films. Flat light-trapping structures only have good electric properties, and rough light-trapping structures only have good optical properties. The support (01) according to the invention has a light-trapping structure (02) which is smooth ("SMART" (SMooth Anti-Reflective Three-dimensional) texture). Additionally, the structured three-dimensional layer (09) is designed with a homogenous and periodic nanostructure (07) and is filled and covered at least with a first anti-reflective layer (10). In this manner, the height of the nanostructure (07) of the structured layer (09) is reduced by at least 30%. The surface angles of the light-trapping structure (02) relative to the superstrate (03) are not greater than 60°. The light-trapping structure (02) of the support (01) according to the invention has both very good optical properties as well as very good electric properties. On the basis of the selected materials, a temperature stability of the support (01) is provided for a liquid-phase crystallization. In a simple and large-scale production method, a nanostructure (07) produced using a nanoimprint process is first smoothed with the anti-reflective layer (10) by means of a spin coating method. In a preferred use, the subsequent thin film structure (14) can be processed by means of a liquid-phase crystallization process.