MoSe2 Back Contact for CIGS Solar Cells
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Solution Overview
Problem
CIGS solar cells face reduced efficiency due to incomplete light absorption, particularly in the near infrared region, resulting from increased bandgap and lower absorption of incident light radiation, which is not effectively utilized for charge generation.
Innovation Solution
A molybdenum-containing back electrode configuration with a controlled thickness of the MoSe2 layer, optimized between 5-15 nm, 35-45 nm, 60-70 nm, or 90-100 nm, is introduced to enhance optical coupling and absorption of reflected light, independent of the CIGS absorber's thickness and extinction coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional Mo back contact is used in CIGS solar cells, then the device structure is simple and manufacturing is easy, but light absorption is incomplete particularly in the near infrared region resulting in reduced efficiency
Solution Approach 1:
The back contact structure is segmented into multiple functional layers: a MoSe2 layer (5-15 nm, 35-45 nm, 60-70 nm, or 90-100 nm thick) positioned between the Mo back contact and the CIGS absorber. This segmentation allows each layer to perform specific functions - the MoSe2 layer optimizes optical coupling and light absorption while the Mo layer provides electrical conductivity, thereby resolving the contradiction between simple structure and high efficiency.
Solution Approach 2:
The invention employs a composite back contact system combining Mo and MoSe2 materials with specific thickness ratios. The MoSe2 layer (with thickness optimized in specific ranges) forms an optical coupling layer that enhances near-infrared light absorption, while the Mo layer provides structural support and electrical conductivity. This composite approach enables simultaneous achievement of structural simplicity and enhanced light absorption efficiency.
2Productivity
If the MoSe2 layer thickness is optimized to specific ranges (5-15 nm, 35-45 nm, 60-70 nm, or 90-100 nm), then light absorption efficiency increases by at least 5%, but the manufacturing precision requirements increase
Solution Approach 1:
The invention identifies specific critical thickness ranges for the MoSe2 layer (5-15 nm, 35-45 nm, 60-70 nm, or 90-100 nm) that optimize optical coupling and light absorption. By defining these discrete parameter ranges rather than requiring continuous optimization, the patent makes the manufacturing process more controllable and reproducible, thereby reducing the actual precision burden while maintaining high light absorption efficiency.
Solution Approach 2:
The MoSe2 layer is formed as a thin, controlled-thickness intermediate layer that can be precisely deposited and then serves its optical coupling function. The specific thickness ranges are chosen to provide optimal performance without requiring excessive material, and the layer's primary function is optical coupling rather than structural support, allowing for precise but cost-effective manufacturing.
3Productivity
If the MoSe2 layer thickness is increased to improve optical coupling, then absorption of reflected light improves, but the layer becomes too thick and may interfere with charge generation
Solution Approach 1:
The patent identifies specific optimal thickness ranges (5-15 nm, 35-45 nm, 60-70 nm, or 90-100 nm) for the MoSe2 layer that maximize optical coupling efficiency while preventing interference with charge generation. These parameter thresholds were determined through optimization to ensure the layer is thick enough for effective optical coupling but thin enough to allow proper charge carrier dynamics in the CIGS absorber.
Solution Approach 2:
The MoSe2 layer serves as an intermediary between the Mo back contact and the CIGS absorber, performing optical coupling functions without interfering with charge generation. The specific thickness ranges are chosen to provide this mediating function - the layer is thick enough to optimize optical coupling and light absorption but thin enough to allow efficient charge carrier extraction, thereby resolving the contradiction between optical performance and electrical 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
This configuration increases solar light absorption by at least 5%, more preferably by 10%, by effectively recycling previously unused light energy, thereby improving the overall efficiency of the photovoltaic device.
Implementation Method 1
A molybdenum-containing back electrode configuration with a controlled thickness of the MoSe2 layer, optimized between 5-15 nm, 35-45 nm, 60-70 nm, or 90-100 nm, is introduced to enhance optical coupling and absorption of reflected light
Data Source
AI summary
A back contact configuration for a CIGS-type photovoltaic device is provided. According to certain examples, the back contact configuration includes an optical matching layer and/or portion of or including MoSe2 having a thickness substantially corresponding to maxima of absorption of reflected light in CIGS-type absorbers used in certain photovoltaic devices. Certain example methods for making the back contact configuration wherein a thickness of the MoSe2 layer and/or portion can be controlled to be within thickness ranges that correspond to maxima of CIGS light absorption for reflected solar light are also provided.