Buried Junctions in CdTe Solar Cells
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Solution Overview
Problem
Current solar cell technologies, particularly CdTe thin film solar cells, face challenges in achieving low manufacturing costs due to slow piece-by-piece production processes and are not suitable for residential rooftop applications due to their weight and rigidity, necessitating the development of flexible substrate-based solar cells that can be manufactured using a continuous roll-to-roll process.
Innovation Solution
A photovoltaic device with a substrate configuration comprising a transparent or opaque substrate, a metal electrode layer, a TCO layer, an absorber layer made of a Group II-VI semiconductor compound, a window layer, and an interface layer between the absorber and window layers, where the absorber layer and/or interface layer include nanoparticles and varying grain sizes, allowing for a buried junction and surface treatments to enhance efficiency and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If piece-by-piece manufacturing process is used for CdTe solar cells, then manufacturing quality can be maintained, but manufacturing cost cannot be reduced below $1/watt due to slow production speed
Solution Approach 1:
The patent implements a continuous roll-to-roll manufacturing process where the substrate continuously moves through deposition chambers, enabling uninterrupted film formation. This eliminates the stop-start nature of piece-by-piece manufacturing, dramatically increasing production throughput while maintaining film quality through controlled continuous deposition conditions.
Solution Approach 2:
The patent changes the manufacturing process parameters from batch-mode to continuous-mode operation. By adjusting deposition rates, substrate temperatures, and chamber pressures to accommodate continuous substrate movement, the process achieves both high speed and high quality, resolving the contradiction between productivity and manufacturing ease.
2Stability of the object's composition
If glass substrates are used for CdTe solar cells, then structural stability is achieved, but weight and rigidity make them unsuitable for residential rooftop applications
Solution Approach 1:
The patent replaces rigid glass substrates with flexible thin-film substrates such as metal foils (stainless steel, aluminum, copper) or polymer films. These flexible substrates dramatically reduce cell weight and enable bending, making the solar cells suitable for residential rooftop applications while maintaining sufficient structural stability through proper substrate selection and device design.
Solution Approach 2:
The patent employs thin, lightweight, and potentially sacrificial substrate materials that can be easily replaced or disposed of after use. This approach prioritizes low weight and flexibility over long-term structural permanence, aligning with the requirements for residential rooftop applications where ease of installation and removal is valuable.
3Manufacturing precision
If vacuum-based CVD process is used for amorphous silicon solar cells, then film quality can be maintained, but manufacturing cost exceeds $2.5/watt due to slow deposition speed
Solution Approach 1:
The patent replaces the mechanical vacuum-based CVD deposition system with a solution-based dip-coating or spray deposition process. This substitution eliminates the need for expensive vacuum chambers and complex mechanical systems, dramatically reducing equipment costs and enabling faster, more economical manufacturing while maintaining acceptable film quality through solution chemistry control.
4Reliability
If evaporation techniques are used for CIGS solar cells, then high conversion efficiency of 10-12% can be achieved, but capital intensive equipment and low process yield make manufacturing cost untenable
Solution Approach 1:
The patent implements continuous roll-to-roll deposition for CIGS thin films, replacing batch-mode evaporation techniques. This continuous process maintains high conversion efficiency through controlled deposition conditions while dramatically improving process yield by eliminating repeated vacuum chamber loading/unloading cycles and enabling uninterrupted production.
Solution Approach 2:
The patent changes the deposition parameters from vacuum evaporation to atmospheric or low-vacuum solution-based deposition. By adjusting solvent composition, deposition temperature, and drying conditions, the process achieves comparable film quality and efficiency with much higher throughput and lower capital equipment requirements.
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 proposed solution enables the production of efficient and cost-effective solar cells suitable for residential rooftop applications by reducing manufacturing costs and improving efficiency through the use of flexible substrates and advanced layer configurations, such as CdTe/CdS devices with graded interface layers and controlled grain sizes, enhancing diffusion and junction formation.
Implementation Method 1
harvest solar energy
Implementation Method 2
enhancing diffusion and junction formation
Data Source
AI summary
The present invention discloses thin film photovoltaic devices comprising Group II-VI semiconductor layers with a substrate configuration having an interface layer between the absorber layer and the window layer to create improved junctions.The present invention also discloses methods for making and surface treatments for thin film photovoltaic devices comprising Group II-VI semiconductor layers with a substrate configuration to create devices with improved junctions.