Photovoltaic Cell Passivating Contact with Uniform Lateral Doping
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Solution Overview
Problem
Existing photovoltaic cell structures face inefficiencies due to limited lateral conductivity and series resistance, particularly on the front side where polysilicon passivating contacts result in optical losses, and there is a need for improved designs that balance passivation and optical transparency.
Innovation Solution
A semiconductor substrate with a passivating layer of polysilicon or similar material, combined with a thin dielectric layer, is used to provide an electrical contact of a specific conductivity type near the surface, aligned with doping in the active region, enhancing lateral conductivity and series resistance, suitable for both single and bi-facial photovoltaic cells, including interdigitated back contact designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polysilicon passivating contacts are used on the front side, then passivation is improved, but optical transparency deteriorates due to optical losses
Solution Approach 1:
The passivating contact structure is segmented into multiple functional layers: a polysilicon layer for passivation, a dielectric layer for optical transparency, and a doped semiconductor layer for electrical contact. This segmentation allows each layer to optimize its specific function without compromising the others.
Solution Approach 2:
The invention uses a composite structure combining polysilicon (for passivation), dielectric material (for optical transparency), and doped semiconductor (for electrical conductivity). This composite approach allows simultaneous achievement of passivation, optical transparency, and electrical contact functionality.
2Reliability
If passivating layers are made thicker to improve passivation, then passivation quality is improved, but lateral conductivity deteriorates
Solution Approach 1:
The invention implements local quality by creating a doped semiconductor layer with uniform lateral dopant distribution specifically in the regions where electrical contact is needed. This localized doping ensures high lateral conductivity only where required, while maintaining good passivation in other areas.
Solution Approach 2:
The invention changes the dopant concentration parameter in the semiconductor layer to achieve uniform lateral conductivity. By optimizing the dopant concentration and distribution, the structure achieves both adequate passivation and sufficient lateral conductivity for electron/hole transport.
3Manufacturing precision
If doping concentration is increased to improve lateral conductivity, then series resistance is reduced, but passivation quality deteriorates
Solution Approach 1:
The structure is segmented into distinct layers with different doping levels: a heavily doped region for lateral conductivity and a lightly doped or intrinsic region for passivation. This segmentation allows optimization of conductivity and passivation independently in different spatial zones.
Solution Approach 2:
Different regions of the structure have different doping characteristics: the semiconductor layer near the surface has uniform lateral doping for conductivity, while the bulk region maintains lower doping for passivation. This local quality variation resolves the contradiction between conductivity and passivation.
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 configuration improves the efficiency of photovoltaic cells by enhancing electron/hole transport and reducing series resistance while maintaining optical transparency, allowing for wider passivating layers without compromising open circuit voltage, and is applicable to various photovoltaic cell types.
Implementation Method 1
wherein a dielectric layer is provided between the first type of passivating layer and an active region of the semiconductor substrate
Implementation Method 2
wherein doping of the first conductivity type is provided in a layer of the active region of the semiconductor substrate near the first surface
Implementation Method 3
The layer of the active region with such a doping underneath the electrode related area will improve lateral conductivity for electron/hole transport locally
Implementation Method 4
a first type of passivating layer for providing an electrical contact of a first conductivity type on a part of the first surface of the semiconductor substrate
Data Source
AI summary
A semiconductor substrate (1) having an active region (2) and a first surface and a second surface facing each other. A first type of passivating layer (5) is present for providing an electrical contact of a first conductivity type on a part of the first surface of the semiconductor substrate (1). A dielectric layer (4) is provided between the first type of passivating layer (5) and an active region (2) of the semiconductor substrate (1). Doping of the first conductivity type is provided in a layer (3) of the active region (2) of the semiconductor substrate (1) near the first surface. The lateral dopant level in the layer (3) of the active region (2) near the first surface is substantially uniform.