ZnS Buffer Layer MOCVD Process for CIGS Solar Cells
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Solution Overview
Problem
Existing CIGS solar cells face challenges in environmental pollution due to hazardous heavy metals like Cd in their buffer layers and have limitations in productivity and photoelectric conversion efficiency.
Innovation Solution
A method involving the formation of a ZnS buffer layer using MOCVD, which replaces CdS, improving productivity and photoelectric conversion efficiency by applying H2O to the ZnS surface, and integrating it with an in-line process for the window layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a CdS buffer layer is used in the solar cell, then the photoelectric conversion efficiency can be maintained, but environmental pollution occurs due to hazardous heavy metal Cd
Solution Approach 1:
The patent changes the material composition parameter by replacing CdS with ZnS in the buffer layer, eliminating hazardous Cd while maintaining the desired photoelectric properties through careful control of ZnS layer characteristics
Solution Approach 2:
The patent converts the potential harm of reduced efficiency from using non-Cd materials into a benefit by demonstrating that ZnS can achieve superior quantum efficiency in UV and IR bands, turning the material substitution challenge into a performance improvement opportunity
2Productivity
If the buffer layer and window layer are formed in separate processes, then each layer can be optimized independently, but productivity decreases due to increased process time
Solution Approach 1:
The patent merges the formation of the buffer layer and window layer into a single MOCVD process step, where both layers are deposited simultaneously in an in-line manner, eliminating process interruptions and improving productivity while maintaining precise control over each layer's properties
Solution Approach 2:
The MOCVD process is designed to perform multiple functions simultaneously - forming both the buffer layer and window layer in one operation, making the process equipment and methodology multi-functional and highly efficient
3Reliability
If the ZnS buffer layer surface is not treated, then the process is simpler, but photoelectric conversion efficiency is reduced
Solution Approach 1:
The patent applies a preliminary surface treatment to the ZnS buffer layer before forming the window layer, preparing the surface in advance to ensure optimal interface properties and maximum photoelectric conversion efficiency, with the treatment being integrated into the overall process flow
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 ZnS buffer layer formed through MOCVD reduces environmental pollution, enhances productivity, and improves photoelectric conversion efficiency, offering superior quantum efficiency in UV and IR bands compared to CdS-based solar cells.
Implementation Method 1
forming a buffer layer including ZnS on the light absorbing layer through an MOCVD scheme by injecting a Zn precursor and an S precursor onto the light absorbing layer
Data Source
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AI summary
A solar cell according to the embodiment includes a substrate; a back electrode layer on the substrate; a light absorbing layer on the back electrode layer; a buffer layer including ZnS on the light absorbing layer; and a window layer on the buffer layer.