P-Type IBC Solar Cell Rear Passivation With Tunnel Oxide Contacts
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Solution Overview
Problem
Conventional p-type IBC solar cells face challenges in selecting a dielectric layer that can effectively passivate both the p-type base and n-type emitter regions without causing surface recombination, as existing dielectric layers with positive or negative surface charges lead to either increased recombination or shunting issues.
Innovation Solution
A back-contacted p-type solar cell design featuring a patterned layer stack of tunnel oxide and n-type polysilicon emitter regions, with alternating areas of n-type and intrinsic polysilicon, utilizing a dielectric layer that provides hydrogen for passivation and is stable under firing conditions, allowing for optimal passivation and reduced recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional solar cell designs with front and rear contacts are used, then current collection is achieved, but surface area for light absorption is reduced and recombination losses increase
Solution Approach 1:
The solar cell structure is segmented into distinct functional zones: n-type semiconductor regions for electron collection and p-type semiconductor regions for hole collection, with each type having separate contact fingers. This segmentation allows current collection without requiring traditional front and rear contacts that would block light, thereby increasing the surface area available for light absorption while maintaining effective current collection pathways.
Solution Approach 2:
The invention transitions from planar front-rear contact geometry to a vertical interdigitated architecture where n-type and p-type regions are stacked in alternating layers with contacts extending vertically. This dimensional reorganization eliminates the need for surface-mounted contacts that block light, maximizing the active light-absorbing surface area while maintaining efficient current collection through the vertical contact structure.
2Reliability
If more contacts are added to improve current collection, then electrical conductivity improves, but manufacturing complexity and device cost increase
Solution Approach 1:
Multiple contact fingers of the same polarity (n-type or p-type) are merged into continuous conductive regions that extend across the solar cell surface. This merging reduces the total number of separate contact elements while maintaining effective current collection area, thereby simplifying manufacturing processes and reducing device complexity without compromising current collection efficiency.
Solution Approach 2:
The interdigitated contact structure serves multiple functions simultaneously: it collects current from respective polarity regions, provides electrical isolation between n-type and p-type contacts, and maintains mechanical stability of the semiconductor layers. This multi-functionality reduces the need for additional specialized components, simplifying the overall device structure and manufacturing.
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 design achieves reduced surface recombination and improved open-circuit voltage by using a dielectric layer that migrates hydrogen during firing, providing effective passivation across the rear surface, thereby enhancing the solar cell's performance.
Implementation Method 1
A solar cell comprises a first n-type semiconductor region and a first p-type semiconductor region arranged in an interdigitated pattern, with each region having associated contact fingers for current collection
Data Source
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AI summary
A back-contacted solar cell based on a silicon substrate of p-type conductivity has a front surface for receiving radiation and a rear surface. The rear surface is provided with a tunnel oxide layer and a doped polysilicon layer of n-type conductivity. The tunnel oxide layer and the patterned doped polysilicon layer of n-type conductivity form a patterned layer stack provided with gaps in the patterned layer stack. An Al-Si alloyed contact is arranged within each of the gaps, in electrical contact with a base layer of the substrate, and one or more Ag contacts are arranged on the patterned doped polysilicon layer and in electrical contact with the patterned doped polysilicon layer.