Passivated Back Contact Structure for IBC Solar Cell Isolation
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Solution Overview
Problem
Conventional interdigitated back contact (IBC) solar cells face issues such as poor isolation effect, increased recombination, and reduced conversion efficiency due to direct contact between n and p regions, as well as challenges in controlling the thickness of the tunneling layer for passivated contact structures.
Innovation Solution
The proposed solution involves a passivated contact structure for solar cells, which includes a first passivated contact region with a doped layer, passivation layer, and another doped layer, and a second passivated contact region with a passivation layer and a doped layer. The second passivated contact region has an opening for connecting a conductive layer, reducing the overall contact area and enhancing isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tunneling layer is used to isolate doped polysilicon from the silicon substrate, then passivation effect is improved, but the thickness control becomes difficult and production scalability is reduced
Solution Approach 1:
The patent introduces an intrinsic semiconductor layer as an intermediary between the doped polysilicon layer and the silicon substrate. This intrinsic layer serves as a mediator that provides both electrical isolation (improving passivation) and a well-defined structural interface that is easier to control during manufacturing, thereby resolving the contradiction between achieving good passivation and maintaining manufacturing precision.
2Loss of energy
If the tunneling layer thickness is reduced to achieve desirable resistivity, then electrical performance is improved, but passivation effect deteriorates
Solution Approach 1:
The patent segments the isolation structure into two distinct functional layers: a thin tunneling layer for electrical connection and charge transport (low resistance), and a thicker intrinsic semiconductor layer for electrical isolation and passivation. This segmentation allows each layer to be optimized independently - the tunneling layer can be kept thin for low resistance while the intrinsic layer provides sufficient thickness for effective passivation, resolving the contradiction between minimizing tunneling resistance and maintaining passivation quality.
3Device complexity
If n region and p region are placed in direct contact to simplify structure, then device complexity is reduced, but recombination increases and conversion efficiency decreases
Solution Approach 1:
The patent places an intrinsic semiconductor layer as an intermediary between the n-type and p-type doped polysilicon regions. This intrinsic layer acts as a mediator that prevents direct contact between oppositely doped regions, thereby eliminating recombination losses at the interface while maintaining structural simplicity. The intrinsic layer is electrically neutral and does not add significant structural complexity, thus resolving the contradiction between simplifying device structure and minimizing recombination losses.
4Ease of manufacture
If electrode is directly printed on doped region to simplify process, then manufacturing steps are reduced, but burn-through occurs during sintering causing electrode contact with silicon substrate
Solution Approach 1:
The patent performs a preliminary action by forming the intrinsic semiconductor layer between the doped polysilicon layer and the silicon substrate before the electrode printing and sintering processes. This preliminary structural preparation creates a protective barrier that prevents burn-through during subsequent high-temperature sintering, ensuring that the electrode remains isolated from the silicon substrate even under thermal stress, thus resolving the contradiction between manufacturing simplicity and contact stability.
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 effectively reduces recombination, enhances the isolation effect, and improves the conversion efficiency of solar cells by minimizing direct contact with the silicon substrate and providing accurate alignment for conductive layer preparation.
Implementation Method 1
the doped polysilicon layer and the silicon substrate are isolated from each other by using the tunneling layer and the passivation layer
Implementation Method 2
the thickness of the tunneling layer has a very large impact on the tunneling resistance
Data Source
AI summary
The disclosure provides a solar cell and a back contact structure thereof, a photovoltaic module, and a photovoltaic system. The back contact structure includes a first doped region having an opposite polarity to a silicon substrate and a second doped region having a same polarity as the silicon substrate. An isolation region is arranged between the first doped region and the second doped region. The protective region arranged on the first doped region includes an insulation layer and a third doped layer having a same polarity as the second doped region. An opening is provided in the protective region to connect the first conductive layer to the first doped region. In the present invention, scratches caused by belt transmission in an existing cell fabrication process is resolved.