Floating Junction Solar Cell Particle Masking Layer
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Solution Overview
Problem
Traditional solar cells with full area Al-BSF suffer from warping, reduced yield, and suboptimal reflection and passivation, leading to charge carrier recombination and reduced efficiency, while floating junctions face shunting issues that decrease passivation effectiveness.
Innovation Solution
A method of forming a floating junction on a solar cell using a particle masking layer, where silicon-containing particles are deposited on the rear surface to create a patterned layer that attenuates phosphorous diffusion, reducing dopant concentration and preventing shunting, allowing for effective rear passivation and metal contact formation without compromising passivation quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If full area Al-BSF is used, then metal contact is achieved, but warping and reduced yield occur
Solution Approach 1:
The patent divides the continuous Al-BSF layer into discrete patterned regions separated by dielectric material. This segmentation prevents the warping issues associated with full area Al-BSF while maintaining necessary metal contact points for charge extraction.
2Reliability
If full area Al-BSF is used, then metal contact is achieved, but suboptimal reflection and passivation occur
Solution Approach 1:
The patent applies different materials and structures to different regions: dielectric material provides passivation in non-contact areas, while patterned Al-BSF regions provide metal contact where needed. This local differentiation optimizes both passivation quality and prevents charge carrier recombination.
3Reliability
If floating junction is formed without particle masking, then rear passivation is achieved, but shunting occurs
Solution Approach 1:
The patent introduces a particle masking layer as an intermediary during the phosphorous diffusion process. This layer prevents excessive dopant accumulation that would cause shunting, while allowing the floating junction to maintain its passivation effectiveness.
4Reliability
If dopant concentration is increased, then conductivity is improved, but recombination increases
Solution Approach 1:
The patent creates local variations in dopant concentration through patterned phosphorous diffusion. High dopant concentration is applied only where metal contact is needed for conductivity, while low dopant concentration is maintained in passivation regions to minimize recombination.
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 approach enhances rear surface passivation, reduces charge carrier recombination, and increases long wavelength light absorption, leading to improved solar cell efficiency by preventing shunting and optimizing dopant distribution.
Implementation Method 1
a second dopant diffusion is performed through the rear surface of the substrate
Implementation Method 2
silicon-containing particles are deposited on the rear surface to create a patterned layer that attenuates phosphorous diffusion
Implementation Method 3
The particle masking layer is then removed to expose the substrate
Implementation Method 4
metal contacts are formed through the dielectric layer
Data Source
AI summary
A method of forming a floating junction on a substrate is disclosed. The method includes providing the substrate doped with boron atoms, the substrate comprising a front surface and a rear surface. The method also includes depositing a set of masking particles on the rear surface in a set of patterns; and heating the substrate in a baking ambient to a first temperature and for a first time period in order to create a particle masking layer. The method further includes exposing the substrate to a phosphorous deposition ambient at a second temperature and for a second time period, wherein a front surface PSG layer, a front surface phosphorous diffusion, a rear surface PSG layer, and a rear surface phosphorous diffusion are formed, and wherein a first phosphorous dopant surface concentration in the substrate proximate to the set of patterns is less than a second dopant surface concentration in the substrate not proximate to the set of patterns. The method also includes exposing the substrate to a set of etchants for a third time period, wherein the front surface PSG layer and the rear surface PSG layer are substantially removed; depositing a front surface SiNx layer and a rear surface SiNx layer; and forming a rear metal contact on the rear surface through the rear surface SiNx layer proximate to the set of patterns.