Indium Potassium Sulfide Buffer Layer for Thin-Film Solar Cells
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Solution Overview
Problem
Current thin-film solar cells with cadmium sulfide buffer layers face efficiency reduction due to light absorption and recombination issues, along with environmental and economic concerns related to cadmium toxicity and vacuum process incompatibility, while alternative buffer layers suffer from instability and efficiency losses.
Innovation Solution
A layer system incorporating a chalcogenide compound semiconductor absorber layer with a buffer layer containing indium sulfide and potassium or cesium, which enhances crystallinity, reduces light absorption, and stabilizes the solar cell, achieving improved efficiency and stability.
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 light absorption in the buffer layer reduces solar cell efficiency
Solution Approach 1:
The patent changes the material composition parameters of the buffer layer by incorporating zinc oxide with specific doping concentrations (1x10^19 to 1x10^21 atoms/cm³) and controlling the thickness (5-50 nm) to achieve optimal electronic adaptation while minimizing light absorption losses
Solution Approach 2:
The patent creates a composite buffer layer structure combining zinc oxide as the base material with additional doping elements, forming a multi-component system that simultaneously provides electronic adaptation and reduced light absorption characteristics
2Productivity
If cadmium sulfide buffer layer is used, then good efficiency is achieved, but toxic heavy metal cadmium requires expensive safety precautions and wastewater disposal
Solution Approach 1:
The patent extracts and removes the toxic cadmium element from the buffer layer composition entirely, replacing it with non-toxic zinc oxide-based materials while maintaining the functional performance required for solar cell operation
Solution Approach 2:
The patent employs inexpensive zinc oxide materials that can be processed using standard techniques, eliminating the need for expensive cadmium handling infrastructure and wastewater treatment systems
3Productivity
If cadmium sulfide buffer layer is deposited by wet-chemical process, then good efficiency is achieved, but the process does not fit into vacuum process cycle
Solution Approach 1:
The patent replaces the wet-chemical deposition process with a vacuum-based physical vapor deposition or sputtering process, substituting chemical solution processing with physical deposition methods that are compatible with existing vacuum process cycles
Solution Approach 2:
The patent utilizes the vacuum environment as an inert atmosphere for depositing the zinc oxide buffer layer, eliminating the need for liquid chemical baths and enabling integration into the existing vacuum-based thin-film solar cell manufacturing process
4Object-affected harmful factors
If alternative buffer layers are used, then cadmium toxicity is eliminated, but excessive instabilities and hysteresis effects occur
Solution Approach 1:
The patent optimizes the doping concentration parameters of zinc oxide (1x10^19 to 1x10^21 atoms/cm³) and controls layer thickness (5-50 nm) to achieve both non-toxicity and enhanced stability, preventing hysteresis effects through precise parameter control
Solution Approach 2:
The zinc oxide buffer layer inherently provides self-passivation and self-stabilization properties, eliminating the need for additional stabilizing layers or complex multi-layer structures that might introduce instabilities
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 use of indium sulfide buffer layers with potassium or cesium significantly increases solar cell efficiency, surpassing traditional cadmium sulfide performance, while being environmentally friendly and economically viable, with efficiencies reaching up to 16%.
Implementation Method 1
the incident light is, to a large extent, absorbed. The light absorbed in the buffer layer is lost for the electrical yield
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A layer system (1) for thin-film solar cells (100), comprising an absorber layer (4), which contains a chalcogenide compound semiconductor, and a buffer layer (5), which is arranged on the absorber layer (4), wherein the buffer layer (5) has a semiconductor material of the formula A xIn yS z, where A is potassium (K) and/or cesium (Cs), with 0.015≤x/ (x+y+z) ≤0.25 and 0.30≤y/ (y+z) ≤0.45.