Photovoltaic Absorber Layers With Diffusion Barrier
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Solution Overview
Problem
Existing photovoltaic absorber materials face efficiency limits due to rapid elemental diffusion during thermal processing, which prevents compositional and elemental grading necessary for effective electron and hole transport and sunlight absorption.
Innovation Solution
The use of multiple absorber layers separated by a diffusion barrier, such as graphene, to prevent elemental intermixing during annealing, allowing for band gap grading by varying the sulfur to selenium ratio or using different light absorbing materials, thereby enhancing light absorption and electron-hole transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If thermal processing is applied to photovoltaic absorbers, then material crystallization and phase formation are achieved, but rapid diffusion of elements occurs driving them to undesired places
Solution Approach 1:
The absorber is divided into multiple discrete layers with different compositions (e.g., Cu-poor layer and Cu-rich layer, or layers with different S/Se ratios). Each layer maintains its distinct compositional characteristics, enabling precise control of the overall compositional profile without elemental diffusion blurring the boundaries between layers.
Solution Approach 2:
A diffusion barrier layer is introduced between adjacent absorber layers to prevent interdiffusion of elements during thermal processing. This intermediary layer acts as a physical barrier that blocks atomic migration while still allowing the structure to undergo necessary annealing for crystallization and phase formation.
2Use of energy by moving object
If compositional grading is implemented to maximize sunlight absorption, then light absorption efficiency is improved, but element diffusion during processing prevents the desired compositional profile from being achieved
Solution Approach 1:
The continuously graded composition is segmented into discrete layers, each with a specific composition optimized for absorbing certain portions of the solar spectrum. This segmentation allows precise control of the compositional profile while preventing diffusion-induced blurring during thermal processing.
Solution Approach 2:
Diffusion barrier layers are positioned between composited graded layers to maintain the integrity of each compositional zone during annealing, ensuring that the desired compositional profile for optimized light absorption is preserved throughout processing.
3Use of energy by moving object
If multi-elemental absorbers are used to increase efficiency, then sunlight absorption is maximized, but rapid diffusion of elements occurs during thermal processing
Solution Approach 1:
Multiple elements are segregated into different spatial zones within the absorber structure. Each zone contains specific elements in controlled proportions, preventing unwanted intermixing during processing while maintaining the multi-elemental complexity needed for high efficiency.
Solution Approach 2:
Diffusion barrier layers are strategically placed between regions containing different elements to prevent interdiffusion during thermal processing. This ensures reliable control of elemental distribution while still allowing the structure to undergo necessary annealing for phase formation and crystallization.
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
This approach effectively prevents elemental diffusion, enabling band gap grading and improving the efficiency of photovoltaic devices by optimizing light absorption and electron-hole transport, as demonstrated by the formation of solar cells with enhanced current-voltage characteristics.
Implementation Method 1
the diffusion barrier prevents diffusion of elements between the first layer of light absorbing material and the second layer of light absorbing material during the annealing
Implementation Method 2
the first layer of light absorbing material has a different band gap from the second layer of light absorbing material
Implementation Method 3
photovoltaic structures having multiple absorber layers separated by a diffusion barrier
Data Source
AI summary
Photovoltaic structures having multiple absorber layers separated by a diffusion barrier are provided. In one aspect, a method of forming an absorber on a substrate includes: depositing a first layer of light absorbing material on the substrate; depositing a diffusion barrier; depositing a second layer of light absorbing material on the diffusion barrier, wherein the first layer of light absorbing material has a different band gap from the second layer of light absorbing material; and annealing the absorber, wherein the diffusion barrier prevents diffusion of elements between the first layer of light absorbing material and the second layer of light absorbing material during the annealing. A solar cell and method for formation thereof are also provided.