Passivated Contact Solar Cell With Backside PN Junction
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Solution Overview
Problem
Passivated contact solar cells face a bottleneck in photoelectric conversion efficiency due to recombination losses and current transmission losses at the light-receiving surface, along with product reliability issues such as high lateral series resistance and poor ultraviolet stability.
Innovation Solution
A solar cell design featuring a double-sided passivating contact structure with a PN junction on the back surface, a local passivating contact on the light-receiving surface, and an N-type diffusion layer, utilizing dielectric layers of varying thicknesses and doping concentrations to enhance carrier transport and surface passivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If passivated contact solar cells are manufactured using industrialized production methods, then manufacturing efficiency is improved, but photoelectric conversion efficiency hits a bottleneck at approximately 25.1%
Solution Approach 1:
The patent applies local quality by implementing a patterned first passivating contact structure on the light-receiving surface rather than uniform coverage. This localized approach reduces recombination losses in critical areas while maintaining manufacturing feasibility. The selective positioning of passivating contacts optimizes photoelectric conversion without requiring complete surface modification.
Solution Approach 2:
The patent moves the PN junction from the light-receiving surface to the back surface of the solar cell. This dimensional relocation eliminates front surface recombination losses while maintaining electrical functionality. The back surface passivating contact structure with through-holes provides both mechanical support and electrical contact without interfering with light absorption at the front surface.
2Loss of energy
If the light-receiving surface is passivated to reduce recombination losses, then photoelectric conversion efficiency is improved, but lateral series resistance increases
Solution Approach 1:
The patent segments the passivating contact structure into multiple components: a patterned first passivating contact structure on the light-receiving surface and a second passivating contact structure on the back surface with through-holes. This segmentation allows current to be collected through multiple pathways, reducing lateral series resistance while maintaining effective surface passivation.
Solution Approach 2:
The N-type diffusion layer acts as an intermediary between the light-receiving surface and the underlying substrate. It provides a low-resistance current collection pathway that reduces lateral series resistance while the overlying passivating contact structure minimizes recombination losses. The diffusion layer mediates between the conflicting requirements of surface passivation and electrical conductivity.
3Loss of energy
If a thin dielectric layer is used in the first passivating contact structure, then carrier transport is improved, but surface passivation quality decreases
Solution Approach 1:
The patent changes the thickness parameter of the dielectric layer in the first passivating contact structure to be thinner than in conventional designs. This parameter change enhances carrier transport by reducing the tunneling barrier thickness. The compensating factor is the optimized doping concentration in the underlying N-type diffusion layer, which maintains surface passivation quality despite the thinner dielectric layer.
4Loss of energy
If a PN junction is formed on the back surface, then photoelectric conversion efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the PN junction formation with the back surface passivating contact structure. The P-type heavily doped polysilicon layer serves dual functions: forming the PN junction with the N-type substrate for improved photoelectric conversion and providing the back surface contact structure with through-holes for mechanical support and electrical connectivity. This merging reduces the number of separate manufacturing steps.
Solution Approach 2:
The second dielectric layer with through-holes serves multiple functions simultaneously: it provides mechanical support for the back surface contact, enables electrical connection between the P-type polysilicon layer and the substrate, and maintains surface passivation. This multi-functionality reduces the need for additional specialized components and simplifies the overall device structure.
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 improves photoelectric conversion efficiency to 25.8% or above by reducing recombination and current transmission losses while enhancing product reliability through improved surface passivation and ultraviolet stability.
Implementation Method 1
an N-type diffusion layer disposed on a light-receiving surface of the N-type substrate
Implementation Method 2
a PN junction being formed between the P-type heavily doped polysilicon layer and the N-type substrate
Implementation Method 3
a first dielectric layer disposed adjacent to the N-type diffusion layer and an N-type doped polysilicon layer disposed away from the N-type diffusion layer
Data Source
Figure 1~2
Figure 3
AI summary
Provided in the present application are a solar cell, a manufacturing method therefor and a photovoltaic module. The solar cell comprises: an N-type substrate (1); an N-type diffusion layer (2) on a light-receiving surface of the N-type substrate (1); a patterned first passivated contact structure (3) on the N-type diffusion layer (2), the patterned first passivated contact structure (3) comprising a first dielectric layer (31) having a thickness of less than or equal to 2 nm and an N-type doped polycrystalline silicon layer (32); and a second passivated contact structure (4) on a backside surface of the N-type substrate (1), the second passivated contact structure (4) comprising a second dielectric layer (41) having a thickness of greater than 2 nm and a P-type heavily doped polycrystalline silicon layer (42), a PN junction being formed on the backside surface, the second dielectric layer (41) having a through hole (411), and the doping concentration of the P-type heavily doped polycrystalline silicon layer (42) being 5×1018 to 3×1020 atoms/cm3. A first functional layer (5) and a first electrode (7) are sequentially provided on the N-type diffusion layer (2) and the first passivated contact structure (3), and a second functional layer (6) and a second electrode (8) are sequentially provided on the P-type heavily doped polycrystalline silicon layer (42).