Group-IV Solar Cell Heterostructure for Multijunction Efficiency

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Solution Overview

Problem

Multijunction photovoltaic cells face efficiency limitations due to high series resistance, parasitic losses, and the need for current matching across subcells, which restricts the number of subcells and reduces the benefit of dividing the solar spectrum into smaller energy ranges.

Innovation Solution

A photovoltaic cell structure with a p-n junction formed at a heterojunction between a group-IV emitter layer and a III-V or group-IV base layer, utilizing tunnel junctions and specific semiconductor materials to reduce minority-carrier recombination and optimize current generation, allowing for the integration of multiple subcells with improved efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple subcells are stacked to divide the solar spectrum into smaller energy ranges, then energy conversion efficiency is improved, but series resistance and parasitic losses increase

Engineering Contradiction:

Improveenergy conversion efficiencyVSAvoidseries resistance and parasitic losses

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The solar cell is divided into multiple subcells stacked in series, with each subcell optimized to absorb a specific energy range of the solar spectrum. This segmentation allows better utilization of different photon energies while the patent addresses the resulting resistance issues through careful junction design

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite heterostructure materials combining group-IV and III-V semiconductors with different bandgaps. This allows creating multiple subcells with optimized optical and electrical properties for each spectral range, while the heterostructure interfaces are engineered to minimize parasitic losses

Inventive Principle:

Principle #40Composite materials

2Productivity

If the number of subcells is increased to improve spectrum utilization, then energy conversion efficiency is improved, but current matching becomes more difficult

Engineering Contradiction:

Improveenergy conversion efficiencyVSAvoidcurrent matching complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

Each subcell is designed with locally optimized properties including specific bandgap materials and thicknesses tailored to its position in the stack. The heterostructure interfaces are engineered with specific doping profiles and composition gradients to optimize carrier collection in each region while maintaining overall current matching

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent varies key parameters such as material composition, layer thickness, and doping concentrations across different subcells to achieve both spectrum division and current matching. The heterostructure band alignment is carefully controlled to facilitate carrier transport while maintaining diode characteristics

Inventive Principle:

Principle #35Parameter changes

3Productivity

If heterostructure interfaces are used to reduce minority-carrier recombination, then efficiency is improved, but manufacturing precision requirements increase

Engineering Contradiction:

ImproveefficiencyVSAvoidinterface quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent introduces carefully engineered intermediate layers and transition regions at heterostructure interfaces. These intermediary layers facilitate gradual composition changes and reduce abrupt discontinuities, thereby minimizing defect formation while maintaining the desired band alignment for efficient carrier collection

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The heterostructure interfaces are designed with preliminary doping profiles and composition gradients that are established during the growth process. This preliminary structuring prevents defect formation and ensures optimal electrical properties before the device enters operation, reducing the need for post-processing corrections

Inventive Principle:

Principle #10Preliminary action

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 the efficiency and voltage of multijunction solar cells by reducing series resistance and parasitic losses, enabling the use of more subcells and improving the division of the solar spectrum, resulting in higher energy conversion efficiency.

Implementation Method 1

photovoltaic cells offer a valuable means for providing power generation by converting the abundant resource of the sun's energy to electrical power

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Implementation Method 2

the subcells within a multijunction cell are often interconnected in series by tunnel junctions between subcells, that act as low resistance contacts

Methodology Applied

Scientific EffectQuantum tunneling:

Data Source

PatentUS11133429B2Group-IV solar cell structure using group-IV or III-V heterostructures

Publication Date: 2021.09.28 THE BOEING CO

AI summary

Device structures, apparatuses, and methods are disclosed for photovoltaic cells that may be a single-junction or multijunction solar cells, with at least a first layer comprising a group-IV semiconductor in which part of the cell comprises a second layer comprising a III-V semiconductor or group-IV semiconductor having a different composition than the group-IV semiconductor of the first layer, such that a heterostructure is formed between the first and second layers.