Electroplated Back Side Surface Field for Solar Cells
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Solution Overview
Problem
Current photovoltaic solar cell manufacturing methods, such as screen printing and vacuum metallization, face challenges like high contact resistance, high paste cost, shadowing, and low throughput, which hinder the production of cost-effective and high-efficiency solar cells.
Innovation Solution
The method involves electroplating a high concentration of p-type dopant atoms onto the back side surface of a semiconductor substrate, followed by annealing to form a P++ back side surface field layer, and optionally depositing a metallic film to create a back side electrical contact, using electrodeposition techniques to overcome the limitations of existing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If screen printing is used to form electrical contacts, then processing simplicity and high throughput are achieved, but high contact resistance, high paste cost, shadowing from wide conductive lines, and mechanical yield loss occur
Solution Approach 1:
The patent replaces the mechanical screen printing process with an electrochemical electrodeposition process. Instead of mechanically forcing paste through screens, the invention uses electrochemical reactions to deposit metal particles and dopants directly onto the semiconductor substrate, eliminating mechanical yield loss and achieving lower contact resistance while maintaining high throughput capability
Solution Approach 2:
The invention creates a composite structure at the contact interface by simultaneously depositing metal particles and dopant atoms during electrodeposition. This composite layer provides both excellent electrical conductivity (low contact resistance) and strong adhesion to the semiconductor substrate, overcoming the limitations of conventional paste materials
2Reliability
If vacuum based metallization processes are used, then contact resistance is reduced and efficiency is improved, but cost increases and throughput decreases
Solution Approach 1:
The patent replaces vacuum-based physical vapor deposition with an electrochemical electrodeposition process conducted in aqueous or non-aqueous solutions at atmospheric pressure. This substitution maintains the ability to form low contact resistance while enabling parallel processing of multiple substrates, thereby achieving both low contact resistance and high throughput
Solution Approach 2:
The invention changes the fundamental processing parameters from vacuum conditions to atmospheric pressure electrochemical conditions. By controlling electrochemical parameters such as current density, deposition time, and solution composition, the process achieves comparable or superior electrical contact properties while dramatically improving throughput and reducing cost
3Ease of manufacture
If screen printing paste is used, then processing is simple, but paste cost is high and shadowing from wide conductive lines reduces efficiency
Solution Approach 1:
The patent replaces expensive screen printing paste with electrochemically deposited metal particles from aqueous or non-aqueous solutions. This substitution eliminates the need for costly organic paste materials while maintaining processing simplicity, as the electrodeposition process is easily controlled through electrical parameters
Solution Approach 2:
The invention changes from using pre-formulated expensive paste materials to using simple metal salt solutions as precursors. The metal particles are generated in-situ during electrodeposition, eliminating the need for costly paste formulations and reducing material costs significantly
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 approach reduces contact resistance, lowers production costs, and enhances the efficiency of solar cells by forming a dense, high-dopant P++ layer that can be fully incorporated into the substrate, potentially increasing substrate thickness and improving electrical performance.
Implementation Method 1
a p-type dopant layer is formed directly on the back side surface by electroplating at least one p-type dopant atom from an electroplating bath
Implementation Method 2
A thermal anneal step follows the formation of the p-type dopant layer which converts a portion of the p-type semiconductor portion of the semiconductor substrate (which is located at the interface with the p-type dopant layer) and the p-type dopant layer into a P++ doped back side surface field layer
Data Source
AI summary
The present disclosure provides a method of forming a back side surface field of a solar cell without utilizing screen printing. The method includes first forming a p-type dopant layer directly on the back side surface of the semiconductor substrate that includes a p/n junction utilizing an electrodeposition method. The p/n junction is defined as the interface that is formed between an n-type semiconductor portion of the substrate and an underlying p-type semiconductor portion of the substrate. The plated structure is then annealed to from a P++ back side surface field layer directly on the back side surface of the semiconductor substrate. Optionally, a metallic film can be electrodeposited on an exposed surface of the P++ back side surface layer.