Sodium Indium Sulfide Buffer Layer for Thin-Film Solar Cells
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Solution Overview
Problem
Current thin-film solar cells using cadmium sulfide (CdS) buffer layers face inefficiencies and environmental concerns due to toxicity, high production costs, and reduced solar cell efficiency caused by light absorption and recombination in the buffer layer, while alternative buffer layers suffer from instability and lower efficiencies.
Innovation Solution
A method for producing a layer system with a sodium indium sulfide buffer layer using sodium thioindate compounds, deposited without indium sulfide, which provides high efficiency and stability, and is environmentally safe, using a molecular formula Na x In y-x/3 S with specific mole fractions and deposited via vacuum methods to prevent oxygen and hydroxide incorporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cadmium sulfide buffer layer is used, then electronic adaptation between absorber and front electrode is achieved, but toxicity and environmental harm increase
Solution Approach 1:
The patent extracts and removes cadmium from the buffer layer composition, replacing it with non-toxic materials such as zinc oxide, zinc sulfide, or their combinations. This eliminates the harmful toxic effects while preserving the buffer layer's essential electronic adaptation function between the absorber and front electrode.
Solution Approach 2:
The patent changes the material composition parameters of the buffer layer from cadmium-based to zinc-based compounds. By adjusting the chemical composition to use non-toxic elements with appropriate bandgap properties, the patent maintains electronic adaptation functionality while eliminating toxicity concerns.
2Reliability
If cadmium sulfide buffer layer is used, then electronic adaptation is achieved, but production costs increase due to safety precautions
Solution Approach 1:
The patent removes cadmium from the buffer layer, eliminating the need for expensive safety precautions, special waste disposal procedures, and regulatory compliance measures associated with handling toxic materials. This directly reduces production costs while maintaining the electronic adaptation function through zinc-based alternatives.
3Reliability
If buffer layer with direct electronic bandgap is used, then electronic adaptation is achieved, but light absorption increases causing efficiency loss
Solution Approach 1:
The patent adjusts the bandgap parameters of the buffer layer materials to achieve an indirect bandgap structure. By selecting zinc oxide and zinc sulfide with appropriate thicknesses and compositions, the buffer layer maintains electronic adaptation while reducing parasitic light absorption, allowing more light to reach the absorber layer for photovoltaic conversion.
4Object-affected harmful factors
If alternative buffer layers to cadmium sulfide are used, then toxicity is reduced, but efficiency and stability decrease
Solution Approach 1:
The patent employs composite buffer layer structures combining zinc oxide and zinc sulfide in specific ratios and configurations. This composite approach leverages the complementary properties of both materials to achieve non-toxic composition while maintaining high efficiency and stability through optimized electronic band alignment and reduced recombination losses.
Solution Approach 2:
The patent optimizes the compositional parameters and thickness of the zinc-based buffer layer to achieve the desired balance between non-toxicity and high performance. By carefully controlling the zinc oxide to zinc sulfide ratio and layer thickness, the patent maintains efficient charge carrier transport and reduces recombination while eliminating cadmium toxicity.
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 sodium indium sulfide buffer layer achieves efficiencies comparable to CdS layers with improved stability and reduced production complexity, ensuring high solar cell performance and environmental safety.
Implementation Method 1
the buffer layer is produced by depositing it from the gas phase onto the absorber layer
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
The invention relates to a method for producing a layer system (1) for thin-film solar cells (100), wherein a) an absorber layer (4) is produced, and b) a buffer layer (5) is produced on the absorber layer (4), wherein the buffer layer (5) contains sodium indium sulfide according to the formula NaxIny-x/3S with 0.063 ≤ x ≤ 0.625 and 0.681 ≤ y ≤1.50, and wherein the buffer layer (5) is produced, without deposition of indium sulfide, based on at least one sodium thioindate compound.