Solar Cell Electrode Design with Passivation Film
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Solution Overview
Problem
The formation of narrow contact or point contact structure electrodes in solar cells is costly due to multiple steps and requires additional materials, and methods like laser-based metal film formation are expensive and complex, failing to fully leverage passivation effects and increasing charge losses at the electrode/silicon interface.
Innovation Solution
A solar cell design where the passivation film is left partially or completely between the collector electrode and silicon, with a second electrode having a lower glass frit content than the first electrode, allowing for reduced charge losses and improved solar cell characteristics while maintaining low manufacturing costs using existing screen-printing technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If narrow contact or point contact structure electrodes are formed to minimize silicon/electrode contact area, then charge losses at the interface are reduced, but manufacturing complexity and cost increase due to multiple additional steps and materials
Solution Approach 1:
The invention extracts the harmful metal-passivation film contact interface by positioning the collector electrode to overlap the first electrode, thereby eliminating direct contact between the collector electrode and the passivation film. This extraction removes the source of charge losses without requiring complex narrow contact or point contact structures, resolving the contradiction between reducing energy loss and maintaining manufacturing simplicity.
2Loss of energy
If laser-based metal film formation is used to create point contact structures, then electrode contact area is minimized, but manufacturing cost increases due to expensive apparatus and additional evaporation steps
Solution Approach 1:
The invention merges the functions of multiple electrodes by having the collector electrode overlap the first electrode, combining their roles into a single structural arrangement. This merging achieves the goal of minimizing harmful contacts while using standard screen-printing technology, avoiding the need for expensive laser apparatus and evaporation steps, thus resolving the contradiction between reducing energy loss and maintaining ease of manufacture.
3Ease of manufacture
If conventional screen-printing with high glass frit content is used for electrode formation, then manufacturing cost is low, but charge losses at the electrode/silicon interface increase
Solution Approach 1:
The invention applies local quality by using a first electrode paste with high glass frit content for the extraction electrode (where good contact is needed) and a second electrode paste with low glass frit content for the collector electrode (where minimal contact with silicon is desired). This localized differentiation allows each electrode to perform its specific function optimally, resolving the contradiction between manufacturing cost and charge losses.
Solution Approach 2:
The invention uses composite electrode structures where the collector electrode is formed by screen-printing a paste containing metal particles and glass frit, creating a composite material that combines the conductive properties of metal with the protective and adhesive properties of glass frit. The controlled low glass frit content in the second paste creates a composite that minimizes unwanted contact while maintaining electrical functionality, resolving the contradiction between cost and performance.
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 design reduces charge losses, enhances short-circuit current and open-circuit voltage, and improves solar cell characteristics while keeping production costs low by utilizing existing screen-printing technology.
Implementation Method 1
heat treating at a temperature of several hundred degree centigrade for bonding to the substrate
Implementation Method 2
screen printing, and firing at a temperature of about 700 to 850°C
Implementation Method 3
A silicon nitride film which is formed by chemical vapor deposition (CVD) or the like is commonly used as the antireflective film
Data Source
Figure 1~3
Figure 4A~5
Figure 6~7
AI summary
A solar cell wherein a passivation film is formed on a crystalline silicon substrate that has at least a p-n junction, and an electrode is formed by printing and heat-treating a conductive paste. Said solar cell has: a first electrode comprising an extraction electrode, which extracts photogenerated carriers from the silicon substrate, formed so as to contact the silicon substrate; and a second electrode comprising a collector electrode, which collects the carriers collected at the extraction electrode, formed so as to contact the first electrode. Other than the point of contact between the first electrode and the second electrode, at least, the second electrode contacts the silicon substrate only partially or not at all. By leaving the passivation film between the collector electrode and the silicon, either completely or partially, the present invention reduces charge losses at electrode/silicon interfaces, improves the short-circuit current and open voltage, and yields a solar cell with improved characteristics. Furthermore, the process can be implemented using existing screen-printing technology or the like, which is extremely effective in reducing costs.