Back Contact Sliver Cells for Silicon Efficiency
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Solution Overview
Problem
Conventional solar cell manufacturing processes, particularly for sliver cells, face challenges in efficient silicon usage and selective diffusion formation due to the need for masking during trench formation, which limits their competitiveness as a renewable energy source.
Innovation Solution
The process involves forming offset trenches on a silicon wafer, allowing line-of-sight deposition of dopant sources and subsequent formation of doped regions, followed by texturing and anti-reflective coating, with all metal contacts on the back side to enhance efficiency and aesthetics, utilizing a bifacial design that collects solar radiation from both sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional sliver cell manufacturing uses micro machining narrow grooves through silicon wafer thickness, then silicon usage is reduced, but masking is required during trench formation which complicates the manufacturing process
Solution Approach 1:
The patent applies preliminary action by forming offset trenches that do not require masking during the diffusion process. The trenches are pre-formed with offsets that naturally define the diffusion regions, eliminating the need for subsequent masking steps while maintaining precise dopant placement.
Solution Approach 2:
The patent segments the trench structure into offset portions, where first and second trenches are formed at different positions and depths. This segmentation allows different dopant sources to be deposited in separate regions without requiring masks, as each trench offset naturally confines the dopant to its intended diffusion zone.
2Reliability
If metal contacts are formed on the front side of the sliver, then electrical connection is achieved, but shading is created that reduces solar radiation collection efficiency
Solution Approach 1:
The patent inverts the conventional contact arrangement by placing all metal contacts on the back side of the sliver instead of the front side. This inversion eliminates front-side shading while maintaining electrical connection through the interdigitated back contact structure that connects to emitter and base regions formed within the sliver.
Solution Approach 2:
The patent transitions the contact configuration from a two-dimensional front-side layout to a three-dimensional back-side interdigitated structure. The metal contacts are positioned on the back surface and extend into trenches that reach the emitter and base regions, utilizing the vertical dimension to achieve electrical connection without front-side shading.
3Ease of manufacture
If conventional solar cell designs are used, then manufacturing is straightforward, but silicon usage efficiency is low compared to sliver cell designs
Solution Approach 1:
The patent applies preliminary action by pre-forming offset trenches and depositing dopant sources in a sequence that eliminates the need for complex masking operations. This preliminary structuring of the silicon wafer with offset trenches maintains manufacturing simplicity while dramatically improving silicon usage efficiency compared to conventional full-wafer solar cells.
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 enables more efficient use of silicon, simplifies manufacturing, increases the surface area for solar radiation collection, and enhances the competitiveness of sliver cells as a renewable energy source by improving efficiency and reducing shading issues.
Implementation Method 1
The solar cell may include an anti-reflective coating formed on the front side of the sliver
Implementation Method 2
The anti-reflective coating may be over a textured surface on the front side of the sliver
Implementation Method 3
Solar cells are well known devices for converting solar radiation to electrical energy
Data Source
AI summary
A solar cell uses a sliver of a silicon wafer as a substrate. The sliver has a front side that faces the sun during normal operation. The front side of the sliver includes a surface from along a thickness of the wafer, allowing for more efficient use of silicon. Metal contacts are formed on the back side of the sliver. The metal contacts electrically connect to the emitter and base of the solar cell, which may be formed within the sliver or be made of polysilicon. The emitter of the solar cell may be a P-type doped region and the base of the solar cell may be an N-type doped region, for example. The solar cell may include an anti-reflective coating formed on the front side of the sliver. The anti-reflective coating may be over a textured surface on the front side of the sliver.