Metal-Wrap-Through Solar Cell Feedthrough Emitter Design
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Solution Overview
Problem
The production of metal-wrap-through (MWT) solar cells is complex and costly due to the need for additional structures like recesses and metallic feed-throughs, which can lead to efficiency losses and short-circuit risks, especially with imprecise processing.
Innovation Solution
A method that forms a feedthrough emitter region on the walls of recesses in the semiconductor substrate and uses an insulating layer on the rear side to electrically isolate the rear-side contact structure from the semiconductor substrate, allowing for cost-effective production by simplifying the process and reducing the risk of short-circuit currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If metallic feed-through structures are produced through recesses to enable back-contacting, then both electrical contacts can be arranged on the back for easier module connection, but the production complexity and costs increase significantly
Solution Approach 1:
The patent segments the contact structure by separating the emitter contact path from the base contact path. The emitter contact is achieved through feed-through structures that extend through the substrate, while the base contact is made through separate rear-side contacts. This segmentation allows independent optimization of each contact type and simplifies the overall manufacturing process by avoiding the need for complex through-substrate vias for both contacts.
Solution Approach 2:
The patent transitions from a planar contact arrangement to a three-dimensional structure by creating recesses in the substrate and forming feed-through structures that extend vertically through the substrate thickness. This dimensional change enables the emitter contact to be made at the rear side while maintaining electrical connection to the front-side emitter region, facilitating back-contacting architecture.
2Ease of operation
If metallic feed-through structures are produced through recesses, then back-contacting is enabled, but ohmic losses and efficiency reductions occur due to charge carrier transport through the substrate
Solution Approach 1:
The patent extracts the emitter contact function from the substrate bulk by creating feed-through structures that provide a direct metallic conduction path through the substrate. This removes the need for charge carriers to travel through the semiconductor substrate to reach the emitter contact, eliminating the associated ohmic losses while maintaining the back-contacting advantage.
Solution Approach 2:
The patent introduces metallic feed-through structures as intermediary elements that provide a low-resistance conduction path between the front-side emitter region and the rear-side emitter contact. These intermediary structures bypass the high-resistance semiconductor substrate path, significantly reducing ohmic losses while enabling the back-contacting architecture.
3Ease of manufacture
If rear-side contact structures are applied directly to the semiconductor substrate, then simple processing is achieved, but short-circuit risks increase due to imprecise processing on the substrate walls
Solution Approach 1:
The patent introduces an insulating layer as an intermediary between the rear-side contact structures and the semiconductor substrate. This insulating layer acts as a protective barrier that prevents direct contact between the metallic contacts and the substrate, eliminating short-circuit risks while allowing simple processing. The insulating layer can be applied as a continuous film that is subsequently patterned or left intact depending on the specific design 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
This approach significantly reduces the complexity and cost of producing MWT solar cells while minimizing efficiency losses, enabling higher charge carrier generation rates and improved solar cell efficiency by avoiding direct contact between the rear-side contact structure and the semiconductor substrate.
Implementation Method 1
uses an insulating layer on the rear side to electrically isolate the rear-side contact structure from the semiconductor substrate
Implementation Method 2
forms a feedthrough emitter region on the walls of recesses in the semiconductor substrate
Data Source
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AI summary
The invention relates to a method for producing a photovoltaic solar cell having a front side designed for coupling in light, comprising the following method steps: A Producing a plurality of cutouts in a semiconductor substrate of a base doping type, B Producing one or more emitter regions of an emitter doping type at least at the front side of the semiconductor substrate, wherein the emitter doping type is opposite to the base doping type, C Applying an electrically insulating insulation layer and D Producing metallic feed through structures in the cutouts, at least one metallic base contact structure at the rear side of the solar cell, which is formed in an electrically conductive manner with the semiconductor substrate in a base doping region, at least one metallic front-side contact structure at the front side of the solar cell, which is formed in an electrically conductive manner with the emitter region at the front side of the semiconductor substrate, and at least one rear-side contact structure at the rear side of the solar cell, which is formed in a manner electrically conductively connected to the feed through contact structure. The invention is characterized in that in method step B and/or a further method step in addition a feed through emitter region of the emitter doping type extending from the front side to the rear side is formed in each case in the semiconductor substrate on the walls of the cutouts, in that in method step C the insulation layer is applied in a manner covering the rear side of the semiconductor substrate, if appropriate further intervening intermediate layers, in that in method step D the rear-side contact structure is applied to the insulation layer, if appropriate to further intermediate layers, in such a way that the rear-side contact structure extends to regions of the semiconductor substrate having base doping and, in these regions, on account of the intervening insulation layer, an electrical insulation is formed between rear-side contact structure and semiconductor substrate, and the base contact structure is applied to the insulation layer, if appropriate to further intermediate layers, in such a way that the base contact structure penetrates through the insulation layer at least in regions, such that an electrically conductive connection is produced between base contact structure and semiconductor substrate. The invention furthermore relates to a photovoltaic solar cell.