Multi-junction Solar Cell Recesses for Photocurrent Matching

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Solution Overview

Problem

Multi-junction solar cells face photocurrent mismatching due to insufficient photocurrent of the silicon (Si) solar cell serving as the bottom cell, leading to efficiency loss, as the top cell's absorption layer has a lower bandgap, causing excessive light absorption and reflection issues.

Innovation Solution

A multi-junction solar cell design with recesses penetrating through the second absorption layer, allowing equal photocurrent generation between top and bottom cells, where the second cell has a higher bandgap, and laser beams are used to selectively remove parts of the second absorption layer and transparent electrode layers to optimize light absorption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a top cell with lower bandgap absorption layer is stacked on a bottom Si solar cell, then light absorption in the top cell increases, but photocurrent mismatching occurs due to excessive light absorption and reflection issues

Engineering Contradiction:

Improvelight absorptionVSAvoidphotocurrent mismatching

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The top cell absorption layer is segmented into multiple regions: a first region with full thickness and a second region with reduced thickness. This segmentation allows different portions of the absorption layer to serve different functions - the first region absorbs light effectively while the second region reduces excessive absorption and reflection, enabling photocurrent matching between top and bottom cells

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the top cell absorption layer are given different local qualities - the first region maintains full thickness for high light absorption, while the second region has reduced thickness to minimize reflection and excessive absorption. This local differentiation resolves the contradiction between needing high light absorption and avoiding photocurrent mismatching

Inventive Principle:

Principle #3Local quality

2Power

If a hybrid multi-junction solar cell is manufactured by sequentially stacking a high-bandgap thin-film and transparent electrode on a sandwich-type crystalline Si cell structure, then photoelectric conversion efficiency equal to or higher than 30% may be achieved, but the structure complexity increases

Engineering Contradiction:

Improvephotoelectric conversion efficiencyVSAvoidstructure complexity

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The top cell structure (absorption layer, buffer layer, transparent electrode) is nested on top of the bottom Si solar cell structure, forming a multi-junction configuration. This nesting approach allows achieving high photoelectric conversion efficiency by combining different cell types while maintaining a relatively compact overall structure that leverages the existing Si industrial system

Inventive Principle:

Principle #7Nested doll (Nesting)

3Manufacturing precision

If laser beams are used to selectively remove parts of the second absorption layer and transparent electrode layers, then photocurrent matching is improved, but the manufacturing process complexity increases

Engineering Contradiction:

Improvephotocurrent matching precisionVSAvoidmanufacturing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Traditional mechanical or chemical etching methods are replaced with laser beam processing to selectively remove portions of the second absorption layer and transparent electrode layers. This substitution enables precise control over the removal process, achieving accurate photocurrent matching through the formation of regions with different thicknesses while maintaining manufacturing feasibility

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enhances photocurrent matching and overall photoelectric conversion efficiency by ensuring equal photocurrents from both cells, thereby reducing efficiency loss and improving the solar cell's performance.

Implementation Method 1

laser beams are used to selectively remove parts of the second absorption layer and transparent electrode layers to optimize light absorption

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

two or more absorption layers having different bandgaps are stacked one another and a high-energy wavelength band and a low-energy wavelength band incident on the same space are absorbed by different absorption layers and are converted into electricity

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Data Source

PatentUS11233165B2Multi-junction solar cell and manufacturing method of the same

Publication Date: 2022.01.25 KOREA INST OF SCI & TECH

AI summary

Provided is a multi-junction solar cell in which two or more absorption layers having different bandgaps are stacked on one another. The multi-junction solar cell includes a first cell including a first absorption layer, and a second cell electrically connected in series onto the first cell, wherein the second cell includes a second absorption layer having a higher bandgap compared to the first absorption layer, and a plurality of recesses penetrating through the second absorption layer.