Backside Contact Solar Cell Electrodes for Lower Wiring Resistance
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Solution Overview
Problem
Backside contact solar cells face issues with high wiring resistance due to additives with low electric conductivity, leading to increased resistance loss and decreased photoelectric conversion efficiency.
Innovation Solution
A backside contact solar cell design featuring a laminated conductor structure for electrodes, where the positive electrode includes a group III element with a higher content ratio and the negative electrode has a lower content ratio, reducing contact and wiring resistance, and incorporating a passivation film to suppress recombination of photo-excited carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a backside contact solar cell structure is used to eliminate optical loss, then photoelectric conversion efficiency improves, but wiring resistance becomes particularly conspicuous due to high photocurrent density
Solution Approach 1:
The electrode structure is segmented into two functional layers that simultaneously address optical loss elimination and wiring resistance reduction. The laminated conductor structure maintains the backside contact advantage while internally optimizing electrical properties to handle high photocurrent density without excessive resistance loss.
Solution Approach 2:
The electrode employs a composite structure combining materials with different properties in two layers. The first layer uses group III element-containing paste for contact optimization, while the second layer uses group III element-reduced paste for conductivity optimization, creating a composite electrode that handles both optical and electrical requirements.
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 solution results in a solar cell with reduced resistance loss and enhanced photoelectric conversion efficiency, manufactured at a lower cost with improved productivity using a simple method.
Implementation Method 1
The p-type region and the n-type region are covered with a passivation film formed mainly of a single layer film or a laminated film of silicon oxide, silicon nitride, aluminum oxide, or silicon carbide, etc. for reducing loss due to recombination of photo-excited carriers.
Implementation Method 2
an opposite surface (light receiving surface) is covered with an antireflection film formed of a single layer film or a laminated film of silicon nitride, titanium oxide, tin oxide, zinc oxide, silicon oxide, or aluminum oxide, etc.
Implementation Method 3
these electrodes are generally formed by applying a conductive paste which has fine metal particles of silver, etc. mixed in an organic binder to predetermined areas by screen plate printing or dispensing, and subsequently performing a heat treatment at approximately several hundred to 850° C.
Data Source
AI summary
A backside contact solar cell has, on a first main surface of a crystal silicon substrate, a p-type region having a p-conductive type and an n-type region having an n-conductive type, and a positive electrode formed on the p-type region and a negative electrode formed on the n-type region, wherein the positive electrode includes a laminated conductor of a first electric conductor which is formed on the p-type region and which includes a group III element and a second electric conductor which is laminated on the first electric conductor and which has a lower content ratio of the group III element than the first electric conductor, and the negative electrode includes the second electric conductor formed on the n-type region. In this way, a low-cost backside contact solar cell has a high photoelectric conversion efficiency.