CIGS Glass Substrate Alkali Diffusion Control
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Solution Overview
Problem
Existing glass substrates for Cu—In—Ga—Se solar cells face challenges in achieving high cell efficiency while maintaining a high glass transition temperature, as increasing alkali content to improve efficiency leads to a decrease in glass transition temperature.
Innovation Solution
A glass substrate with specific compositional ratios of Ca, Sr, Ba, and Na, and oxide content, optimized for thermal expansion and diffusion properties, ensuring a glass transition temperature of at least 580°C and efficient Na diffusion into the CIGS layer during heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If alkali content is increased to improve cell efficiency, then cell efficiency is improved, but glass transition temperature decreases
Solution Approach 1:
The invention changes the chemical composition parameters of the glass substrate by strictly controlling the alkali content (Na2O: 2-11 mass%, K2O: 2-21 mass%) and the ratio Na2O/(CaO+SrO+BaO) ≤ 1.2, while adjusting the total alkali metal oxide content to 4-22 mass%. This parameter optimization resolves the contradiction by finding the optimal balance point where cell efficiency is maximized while glass transition temperature remains above 580°C.
Solution Approach 2:
The invention creates a composite glass system combining multiple oxide components (SiO2, Al2O3, MgO, CaO, SrO, BaO, Na2O, K2O, ZrO2) with specific compositional ratios. This composite material approach allows the glass substrate to simultaneously achieve high cell efficiency through optimized alkali content and high glass transition temperature through the synergistic effect of multiple oxides, particularly the alkaline earth metals (CaO+SrO+BaO: 2-23 mass%) that provide thermal stability.
2Temperature
If glass transition temperature is increased to maintain structural stability, then glass transition temperature is improved, but cell efficiency decreases
Solution Approach 1:
The invention optimizes the glass composition parameters by setting specific ranges for each oxide component and their ratios. The glass transition temperature is maintained above 580°C through controlled composition (particularly CaO+SrO+BaO: 2-23 mass% and SiO2: 53-72 mass%), while the cell efficiency is improved by optimizing the total alkali metal oxide content (4-22 mass%) and the ratio Na2O/(CaO+SrO+BaO) ≤ 1.2, thus resolving the contradiction between thermal stability and photoelectric performance.
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 optimized glass substrate achieves high cell efficiency and a high glass transition temperature, enabling the production of solar cells with improved performance and cost-effectiveness.
Implementation Method 1
the ratio of the average Na amount (atom %) within from 10 to 40 nm in depth from the surface of the glass substrate after a heat treatment at 600° C. under a N2 atmosphere for 1 hour to such average Na amount before the heat treatment is at least 1.5
Implementation Method 2
after a heat treatment at 600° C. under a N2 atmosphere for 1 hour
Data Source
AI summary
A glass substrate for a CIGS solar cell, having high cell efficiency and high glass transition temperature is provided. The glass substrate for a vapor-deposited CIGS film solar cell has a glass transition temperature of at least 580° C. and an average thermal expansion coefficient of from 70×10−7 to 100×10−7/° C., wherein the ratio of the average total amount of Ca, Sr and Ba within from 10 to 40 nm in depth from the surface of the glass substrate to the total amount of Ca, Sr and Ba at 5,000 nm in depth from the surface of the glass substrate is at most 0.35, and the ratio of the average Na amount within from 10 to 40 nm in depth from the surface of the glass substrate after heat treatment to such average Na amount before the heat treatment is at least 1.5.