Photovoltaic Cell Emitter Doping for Low Contact Resistivity
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Solution Overview
Problem
Existing photovoltaic cell manufacturing techniques result in a rapid decrease in doping concentration along the thickness direction of the first doped layer, leading to reduced electrical properties and higher contact resistivity between the emitter and metal electrode, which affects the conversion efficiency and stability of the photovoltaic cell.
Innovation Solution
A photovoltaic cell design with a substrate having a selective emitter structure, where the doping concentration change between different planes is controlled within specific limits (ΔC1≤15%, ΔC2≤30%, and ΔC3≤25%), and a method involving dual-laser doping with different wavelengths and energy densities to maintain consistent doping concentration, enhancing the emitter's electrical properties and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single wavelength laser or post-oxidation process is used for doping, then the doping process is simple, but the doping concentration decreases rapidly along the thickness direction
Solution Approach 1:
The doping process is segmented into multiple steps using different laser wavelengths. The first laser (first wavelength) performs initial doping to form a first doped layer, while the second laser (second wavelength) performs subsequent doping to form a second doped layer. This segmentation allows each laser to target specific depth ranges, preventing rapid concentration decay and improving overall doping uniformity.
Solution Approach 2:
The patent changes the laser wavelength parameter from a single wavelength to dual wavelengths. The first laser uses a wavelength optimized for shallow doping, while the second laser uses a different wavelength for deeper doping. This parameter change enables precise control over doping concentration distribution, maintaining consistent concentration along the thickness direction.
2Productivity
If doping concentration decreases rapidly along thickness direction, then the doping process is faster, but contact resistivity between emitter and metal electrode increases
Solution Approach 1:
The emitter is segmented into a first doped layer and a second doped layer at different depths. The first doped layer provides high doping concentration for low contact resistivity, while the second doped layer extends the doping region deeper into the substrate. This segmentation maintains both fast processing and reliable electrical contact.
Solution Approach 2:
The patent extends the doping solution from a one-dimensional shallow doping approach to a two-dimensional approach by adding depth control through dual-wavelength lasers. This allows simultaneous optimization of surface contact properties and bulk electrical properties, resolving the contradiction between processing speed and contact reliability.
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 controlled doping concentration improves the consistency of the first doped layer, reduces contact resistivity, and enhances the conversion efficiency and stability of the photovoltaic cell by ensuring a stable ohmic contact between the emitter and metal electrode.
Implementation Method 1
directing a first laser through the doping reagent into the second plane to diffuse the target element to the first doped layer and the second doped layer
Implementation Method 2
driving the target element to diffuse to the second doped layer by the high temperature generated by the first lase
Implementation Method 3
directing a second laser through the doping reagent into the third plane to diffuse the target element of the second doped layer to the first doped layer
Implementation Method 4
driving the target element to diffuse to the first doped layer by the high temperature generated by the second laser
Data Source
AI summary
The present disclosure relates to a photovoltaic cell and a method for manufacturing a photovoltaic cell. The photovoltaic cell includes a substrate including an emitter and a passivation layer stacked in sequence on one side of the substrate. The emitter includes a first plane and a second plane laminated along a thickness direction of the emitter, and part of the emitter between the second plane and the first plane is a first doped layer. Within a unit volume, a rate of change ΔC1 between doping concentration of the second plane and doping concentration of the first plane satisfies: ΔC1≤15%.