Triple-Junction Photovoltaic Cell Band Gap Optimization

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Solution Overview

Problem

Current compound semiconductor photovoltaic cells face inefficiencies due to lattice mismatch issues and energy loss caused by inappropriate band gap alignment, leading to reduced energy conversion efficiency and increased manufacturing costs.

Innovation Solution

A triple-junction photovoltaic cell structure is developed, utilizing InP and GaAs substrates with specific band gap alignments and materials like GaInPAs, GaInAs, and GaInP cells, along with tunnel junctions and bonding layers, to optimize energy conversion and reduce energy loss by ensuring light is effectively absorbed across the cells.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a lattice-matched triple-junction photovoltaic cell structure is used with Ge substrate, then the manufacturing process is simplified and lattice mismatch is reduced, but the band gap balance is not optimal and current balance is poor

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidband gap balance and current balance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The photovoltaic cell is divided into three separate junction layers (GaInP, GaAs, GaInAs) with distinct band gaps (1.9 eV, 1.42 eV, 1.0 eV), each optimized for specific wavelength ranges of sunlight. This segmentation allows independent optimization of each layer's band gap to achieve both manufacturing feasibility and optimal current balance across the spectrum.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the band gap parameters of the three junction layers to 1.9 eV, 1.42 eV, and 1.0 eV respectively, deviating from traditional lattice-matched configurations. This parameter optimization achieves better current balance while maintaining lattice matching through careful material composition control in the GaInP and GaInAs layers.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the band gap of the bottom cell is increased to improve current balance, then energy conversion efficiency increases, but the material selection and structure complexity increase

Engineering Contradiction:

Improvecurrent balanceVSAvoidmaterial selection and structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention uses composite material systems: GaInP for the top junction, GaAs for the middle junction, and GaInAs for the bottom junction. These compound semiconductors allow precise control of band gap parameters while maintaining lattice matching, achieving optimal current balance without excessive structural complexity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Instead of starting with a fixed substrate and adapting layer band gaps, the invention inverts the approach by first establishing the optimal band gap sequence (1.9 eV/1.42 eV/1.0 eV) for maximum current balance, then selecting materials and substrate configurations that achieve these parameters while maintaining manufacturability.

Inventive Principle:

Principle #13The other way round (Inversion)

3Productivity

If compound semiconductor materials are used to achieve high energy conversion efficiency, then the efficiency is approximately two times higher than silicon photovoltaic cells, but the substrate cost is high and manufacturing cost increases significantly

Engineering Contradiction:

Improveenergy conversion efficiencyVSAvoidmanufacturing cost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The invention applies local quality optimization by carefully controlling the composition and thickness of each junction layer (GaInP, GaAs, GaInAs) to achieve optimal light absorption and current generation in specific wavelength ranges. This localized optimization maximizes energy conversion efficiency while using materials and structures that are more cost-effective than alternative high-efficiency designs.

Inventive Principle:

Principle #3Local quality

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 proposed structure enhances energy conversion efficiency and reduces manufacturing costs by minimizing energy loss and improving band gap alignment, leading to higher performance and reliability in compound semiconductor photovoltaic cells.

Implementation Method 1

compound semiconductor photovoltaic cell

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Data Source

PatentEP2973745B1Compound semiconductor photovoltaic cell and manufacturing method of the same

Publication Date: 2021.04.28 RICOH CO LTD

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AI summary

A compound semiconductor photovoltaic cell includes a compound semiconductor substrate; one or more first photoelectric conversion cells deposited on the compound semiconductor substrate; a bonding layer deposited on the one or more first photoelectric conversion cells; and one or more second photoelectric conversion cells bonded to the one or more first photoelectric conversion cells via the bonding layer, and disposed on a light incident side of the one or more first photoelectric conversion cells in a light incident direction. Further, band gaps of the first and the second photoelectric conversion cells decrease as the first and the second photoelectric conversion cells approach from the light incident side toward a back side in the light incident direction, and when there is one second photoelectric conversion cells, a band gap of the bonding layer is greater than or equal to a band gap of the second photoelectric conversion cell.