Bifacial Photovoltaic Cell Doping Sequence for Lifetime Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bifacial photovoltaic cell manufacturing processes face challenges in achieving high efficiency due to boron diffusion-associated degradation and cross-doping issues, leading to increased back surface recombination and reduced minority carrier bulk lifetime.
Innovation Solution
A manufacturing process involving sequential deposition and diffusion of boron and phosphorous layers, followed by texturing and passivating/antireflective coating, to control boron concentration and minimize B-Si compound formation, thereby enhancing cell performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If boron is used as a p-dopant for p+ layer formation, then back surface recombination is reduced, but bulk lifetime is degraded
Solution Approach 1:
A boron-containing layer is deposited on the second surface of the substrate before any other processing steps. This preliminary deposition ensures controlled boron distribution from the outset, preventing excessive boron diffusion into the bulk that would degrade lifetime while still providing sufficient boron at the surface to reduce back surface recombination.
Solution Approach 2:
A cap layer is formed over the boron-containing layer on the second surface, creating a localized boron source that is confined to specific regions. This allows boron to be present where needed (at the surface for reducing recombination) while limiting its diffusion into the bulk, thus resolving the contradiction between reducing back surface recombination and maintaining bulk lifetime.
2Adaptability or versatility
If different dopant sources are used for phosphorus and boron deposition, then doping flexibility is improved, but cross-doping and process complexity increase
Solution Approach 1:
The doping process is segmented into distinct stages: first, a boron-containing layer is deposited on the second surface; then a cap layer is formed;接着, the cap layer is removed from certain regions to expose the boron-containing layer; finally, phosphorus is deposited. This segmentation allows precise control over where each dopant is present, preventing cross-doping while maintaining flexibility.
Solution Approach 2:
The boron-containing layer is deposited and the cap layer is formed in advance, before phosphorus deposition. This preliminary action establishes a protected boron source that will only be exposed in specific regions later, allowing flexible doping patterns without requiring complex simultaneous deposition processes.
3Reliability
If boron diffusion is increased to reduce back surface recombination, then recombination loss is reduced, but bulk lifetime is further degraded
Solution Approach 1:
The cap layer is removed from specific regions of the second surface, creating localized areas where boron can diffuse. This selective removal ensures boron diffusion is concentrated where needed for reducing back surface recombination, rather than occurring uniformly throughout the bulk, thus limiting lifetime degradation.
Solution Approach 2:
The boron-containing layer is deposited and protected by the cap layer before any diffusion-inducing steps. This preliminary setup allows the process to proceed with controlled boron release, ensuring diffusion occurs only when and where intended, balancing recombination reduction with lifetime preservation.
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 process results in improved front and rear illumination efficiency, with reduced back surface recombination and increased short circuit current density, open circuit voltage, and fill factor.
Implementation Method 1
Coating a substrate with a boron containing layer
Implementation Method 2
effecting diffusion of the phosphorous and the boron into the substrate
Implementation Method 3
Texturing creates micro pyramid-like shapes on the surface of the substrate, thus ultimately increasing the light absorption
Implementation Method 4
forming a passivating and antireflective layer on the substrate's second surface
Data Source
AI summary
A process for manufacturing a bifacial photovoltaic cell, comprising the steps: coating a substrate with a boron containing layer; forming a cap layer over the boron containing layer which is on the second surface of the substrate; removing the boron containing layer from the surfaces of the substrate which are not covered with a cap layer; effecting the deposition of a phosphorous containing layer on the surfaces of the substrate which are not covered by the cap layer, and effecting diffusion of the phosphorous and the boron into the substrate; removing the phosphorous containing layer; texturing the substrate where there is no cap layer; effecting the deposition of a phosphorous containing layer on the first surface of the substrate and effecting diffusion of phosphorous into the substrate to form a second n-doped layer; and forming a passivating and/or antireflective coating layer covering the n-doped layer on the substrate's first surface.