Back Contact Cell Electrode Structure for Reliability

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Solution Overview

Problem

Existing back contact solar cells face challenges with high costs, low reliability, and poor photoelectric conversion performance due to issues with electrode structure design, including high-temperature paste reliability, stress concentration during assembly, and recombination loss from long-distance electron-hole pair diffusion.

Innovation Solution

The electrode structure for back contact cells features a design with first and second fingers, busbars, and pad points, where the pad points are positioned away from the edge, allowing for efficient current collection without the need for extensive insulation paste, enabling the use of high-temperature paste and reducing the distance electrons and holes need to travel, thus enhancing reliability and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If insulation paste is used to insulate electrodes of opposite polarities, then insulation is achieved, but the paste cannot withstand high temperature and requires post-printing pad points and bus bars, increasing costs and reducing reliability

Engineering Contradiction:

Improvepaste reliabilityVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Instead of insulating electrodes of opposite polarities, the patent inverts the approach by making pad points and bus bars of the same polarity adjacent to each other at the edge. This eliminates the need for insulation paste between opposite polarity electrodes, allowing high-temperature paste to be used throughout the manufacturing process, thereby improving reliability and simplifying the manufacturing process.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent extracts the insulation requirement from the electrode design by repositioning same-polarity electrodes to the edge. This removes the need for insulation paste between opposite polarity electrodes, eliminating the associated manufacturing complexities and reliability issues with low-temperature paste.

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of manufacture

If pad points and bus bar are located at the farthest edge of silicon wafer, then assembly is simplified, but stress concentration during welding causes microcracks and reduces yield

Engineering Contradiction:

Improvemodule assembly easeVSAvoidmodule yield

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality by positioning pad points and bus bars at specific locations - same polarity electrodes are placed at the edge while opposite polarity electrodes remain in the center. This localized differentiation allows edge placement for assembly simplicity while avoiding stress concentration issues by not placing all electrodes at the extreme edge.

Inventive Principle:

Principle #3Local quality

3Reliability

If outer pad points and bus bar are disposed at a distance from the edge, then stress concentration is reduced, but photo-generated electron-hole pairs must diffuse long distances, causing recombination loss and poor photoelectric conversion

Engineering Contradiction:

Improvecrack resistanceVSAvoidrecombination loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent inverts the conventional approach by placing same-polarity pad points and bus bars at the edge rather than distancing them from the edge. This edge placement minimizes the diffusion distance for electron-hole pairs, reducing recombination losses and improving photoelectric conversion efficiency, while same-polarity placement avoids stress concentration issues.

Inventive Principle:

Principle #13The other way round (Inversion)

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 costs, improves product yield, and ensures high photoelectric conversion efficiency by eliminating the need for extensive insulation paste and minimizing recombination losses, leading to improved module reliability and performance.

Implementation Method 1

A solar cell is a semiconductor device capable of converting light energy to electric energy

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Data Source

PatentUS11688816B1Electrode structure of back contact cell, back contact cell, back contact cell module, and back contact cell system

Publication Date: 2023.06.27 SOLARLAB AIKO EUROPE GMBH

AI summary

The disclosure provides an electrode structure of a back contact cell, a back contact cell, a back contact cell module, and a back contact cell system. The electrode structure includes: first fingers, configured to collect a first polarity region; second fingers, configured to collect a second polarity region; a first busbar, disposed on a side of the back contact cell close to a first edge and connected to the first fingers; first pad points; and first connection electrodes, respectively connected to the first busbar and the first pad points. A distance between each of the first pad points and the first edge is greater than a distance between the first busbar and the first edge. The electrode structure can improve the reliability, reduce the costs, increase the product yield, and ensure excellent photoelectric conversion efficiency.