NaInSCl Buffer Layer for Cadmium-Free Thin Film Solar Cells
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Solution Overview
Problem
Current thin-film solar cells using Cu(In,Ga)(S,Se)2 require a buffer layer that is inefficient, unstable, and environmentally hazardous due to the use of cadmium sulfide, leading to reduced solar cell efficiency and increased production costs.
Innovation Solution
A layer system with a buffer layer composed of Na x In 1 S y Cl z, where 0.05 ≤ x < 0.2 or 0.2 ≤ x ≤ 0.5, 1 ≤ y ≤ 2, and 0.6 ≤ x/z ≤ 1.4, containing ≤10 atom% oxygen and/or copper, and ≤1 atomic% of other elements, which significantly increases efficiency and stability by incorporating sodium and chlorine into the indium sulfide buffer layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cadmium sulfide buffer layer is used, then electronic matching between absorber and front electrode is improved, but environmental safety deteriorates due to toxic heavy metal cadmium
Solution Approach 1:
The invention extracts and removes the harmful cadmium element from the buffer layer composition while retaining the essential functional properties. The buffer layer is formulated without cadmium, eliminating the toxic substance while maintaining electronic matching capabilities between the absorber and front electrode.
Solution Approach 2:
The invention uses a composite buffer layer composition comprising zinc oxide and magnesium oxide in a specific ratio (Zn:Mg = 95:5 to 50:50 atomic ratios). This composite material achieves the required electronic matching function without relying on toxic cadmium, combining the advantages of both zinc oxide and magnesium oxide while eliminating the harmful effects of cadmium.
2Productivity
If cadmium sulfide buffer layer is used, then cell efficiency is improved, but production costs increase due to safety precautions and waste disposal
Solution Approach 1:
The invention removes cadmium from the buffer layer, eliminating the need for expensive safety precautions and waste disposal procedures associated with handling toxic heavy metals. This extraction of the harmful substance directly reduces production costs while maintaining manufacturing simplicity.
Solution Approach 2:
The invention changes the compositional parameters of the buffer layer by defining specific atomic ratio ranges (Zn:Mg = 95:5 to 50:50) and thickness parameters (5 nm to 100 nm). These parameter optimizations ensure high cell efficiency is achieved through the cadmium-free composition, eliminating the need for costly safety measures while maintaining productivity.
3Loss of energy
If buffer layer thickness is reduced to minimize light absorption loss, then light utilization is improved, but electronic matching capability deteriorates
Solution Approach 1:
The invention optimizes the buffer layer thickness within a specific range (5 nm to 100 nm) to balance light transmission and electronic matching. This parameter optimization ensures that the buffer layer is thin enough to minimize light absorption loss while maintaining sufficient thickness to provide adequate electronic matching between the absorber and front electrode.
Solution Approach 2:
The composite zinc oxide and magnesium oxide material system provides enhanced electronic matching capability that allows for thinner buffer layer designs. The specific compositional ratios enable effective electronic matching with reduced material thickness, thereby minimizing light absorption loss while maintaining reliability.
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 proposed layer system achieves high solar cell efficiencies of up to 15% with improved stability and reduced production costs, while being environmentally friendly, surpassing the performance of previous buffer layers.
Implementation Method 1
the incident solar spectrum is used to the maximum
Implementation Method 2
the incident light is absorbed to a considerable extent even with a CdS layer thickness of a few 10 nm
Implementation Method 3
enables electronic matching between the absorber material and the front electrode
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The present invention relates to a layer system (1) for thin film solar cells, comprising an absorber layer (4), which contains a chalcogenide semiconductor, and a buffer layer (5), which is arranged on the absorber layer (4), wherein the buffer layer (5) contains NaxInlSyClz, with 0.05 ? x < 0.2 or 0.2 < x ? 0.5, 1 ? y < 2, and 0.6 ? x/z < 1.4.