Back Contact Solar Cell With Dot-Shaped Base Diffusion Regions
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Solution Overview
Problem
Conventional solar cells face efficiency limitations due to increased minority charge carrier recombination and series resistance losses associated with lateral transport of charge carriers, particularly when the pitch of diffusion regions is larger than the wafer thickness.
Innovation Solution
The implementation of a back side contact solar cell structure with reduced area base diffusion regions of a dot shape, surrounded by a continuous emitter diffusion region, which minimizes minority charge carrier recombination losses while maintaining low series resistance losses by promoting vertical transport of charge carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the pitch of diffusion regions is increased, then the manufacturing cost is reduced, but minority charge carrier recombination losses increase
Solution Approach 1:
The solar cell structure segments the diffusion regions into functionally distinct base diffusion regions and emitter diffusion regions. Base diffusion regions have larger area optimized for collecting minority charge carriers, while emitter diffusion regions have smaller area optimized for extracting majority charge carriers. This segmentation allows each region to be optimized for its specific function, reducing overall recombination losses while maintaining manufacturable pitch dimensions.
Solution Approach 2:
Different regions of the solar cell are given different properties: base diffusion regions are designed with larger area and positioned to maximize minority carrier collection, while emitter diffusion regions are designed with smaller area and positioned for efficient majority carrier extraction. This local differentiation of properties allows simultaneous optimization of carrier collection and resistance reduction without requiring uniformly small pitch across the entire cell.
2Productivity
If the base diffusion region area is increased, then minority charge carrier collection is improved, but series resistance losses due to lateral flow of majority charge carriers increase
Solution Approach 1:
The diffusion structure is segmented into base diffusion regions for minority carrier collection and separate emitter diffusion regions for majority carrier extraction. By providing dedicated emitter regions positioned near the base regions, majority carriers have short lateral transport paths to reach extraction points, reducing series resistance losses even when base regions are large enough to effectively collect minority carriers.
Solution Approach 2:
Emitter diffusion regions act as intermediary structures between the large-area base diffusion regions and the metal contacts. These intermediary regions provide localized collection points for majority carriers generated in the base regions, reducing the lateral transport distance and associated resistance losses while allowing the base regions to maintain large area for effective minority carrier collection.
3Ease of manufacture
If conventional diffusion region structures are used, then manufacturing is simplified, but efficiency is limited due to recombination and resistance losses
Solution Approach 1:
The solar cell employs segmented diffusion regions with distinct functions - base diffusion regions optimized for minority carrier collection and emitter diffusion regions optimized for majority carrier extraction. This segmentation can be implemented using standard photolithography and diffusion processes, maintaining manufacturing simplicity while significantly improving efficiency by reducing both recombination losses and series resistance losses through optimized regional functionality.
Solution Approach 2:
Different local regions are optimized for different functions: base diffusion regions with properties optimized for minority carrier collection and emitter diffusion regions with properties optimized for majority carrier extraction. This local quality differentiation allows the cell to overcome the efficiency limitations of conventional uniform structures while still using standard manufacturing processes to create the differentiated regions.
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 design enhances solar cell efficiency by reducing minority charge carrier recombination and series resistance losses, allowing for higher power generation capabilities, even with lower quality silicon substrates, and offers a cost-effective fabrication process.
Implementation Method 1
Solar cells are well known devices for converting solar radiation to electrical energy
Implementation Method 2
a solar cell may be fabricated by forming P-type and N-type diffusion regions in a silicon substrate
Data Source
AI summary
In one embodiment, a solar cell has base and emitter diffusion regions formed on the back side. The emitter diffusion region is configured to collect minority charge carriers in the solar cell, while the base diffusion region is configured to collect majority charge carriers. The emitter diffusion region may be a continuous region separating the base diffusion regions. Each of the base diffusion regions may have a reduced area to decrease minority charge carrier recombination losses without substantially increasing series resistance losses due to lateral flow of majority charge carriers. Each of the base diffusion regions may have a dot shape, for example.