Tandem Photovoltaic Cells With Optical Filters for Spectral Segmentation

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Solution Overview

Problem

Multi-junction organic solar cells face performance limitations due to broad absorption spectra of quantum dot cells, which absorb shorter wavelength photons, preventing them from being transmitted or reflected to other sub-cells tuned for those regions, thereby reducing overall efficiency.

Innovation Solution

Incorporating an optical filter layer, such as a Distributed Bragg Reflector (DBR) or photonic crystal, to selectively tune the wavelengths of reflection, transmission, or absorption, allowing long wavelength light to be transmitted through or reflected, while short wavelength light is absorbed in the top layer, thereby optimizing the absorption spectrum of multi-junction solar cells.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If quantum dot solar cells are used to cover the near infrared spectrum, then power conversion efficiency is improved, but shorter wavelength photons are absorbed and cannot be transmitted to other sub-cells, reducing overall multi-junction performance

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoidbroad absorption spectrum blocking shorter wavelength photons

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The quantum dot solar cell is divided into multiple sub-cells, each tuned to absorb specific wavelength regions. The first sub-cell absorbs visible light while the second sub-cell absorbs near-infrared light, allowing spectral segmentation that prevents broad absorption from blocking shorter wavelength photons.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An intermediate optical filter is introduced between the quantum dot sub-cells to selectively transmit or reflect specific wavelength ranges. This intermediary component ensures that shorter wavelength photons not absorbed by the first sub-cell can be directed to subsequent sub-cells, resolving the blocking issue.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If conventional organic photoactive materials are used, then the device structure is simpler, but they do not efficiently absorb and generate electrical energy in the near infrared solar spectrum

Engineering Contradiction:

Improvedevice structureVSAvoidnear infrared absorption efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent combines conventional organic photoactive materials with quantum dot materials in a multi-junction structure. The organic materials maintain simplicity in fabrication while quantum dots provide enhanced near-infrared absorption, creating a composite system that achieves both goals.

Inventive Principle:

Principle #40Composite materials

3Productivity

If multi-junction structure is implemented to increase absorption spectrum, then performance is improved, but thermalization losses occur when photons with greater energy than band gap are absorbed

Engineering Contradiction:

Improveabsorption spectrum coverageVSAvoidthermalization losses

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The absorption spectrum is segmented across multiple sub-cells, each with tailored band gaps. The first sub-cell has a larger band gap for visible light absorption, while the second sub-cell has a smaller band gap for near-infrared absorption, ensuring that photons are absorbed by the sub-cell with the appropriate band gap match, minimizing thermalization losses.

Inventive Principle:

Principle #1Segmentation

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 configuration enhances the absorption spectrum of multi-junction solar cells, increasing power conversion efficiency by ensuring that each sub-cell absorbs the appropriate wavelengths, maximizing energy generation without thermalization losses.

Implementation Method 1

Incorporating an optical filter layer, such as a Distributed Bragg Reflector (DBR) or photonic crystal, to selectively tune the wavelengths of reflection, transmission, or absorption

Methodology Applied

Scientific EffectOptical interference: Interference

Implementation Method 2

Multi-junction photovoltaic cells provide superior performance over single junction solar cells by increasing the wavelengths of the solar spectrum that can be absorbed by the photovoltaic cell

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Data Source

PatentUS11889709B2Mechanically stacked tandem photovoltaic cells with intermediate optical filters

Publication Date: 2024.01.30 THE RGT UNIV OF MICHIGAN

AI summary

A method of fabricating a multi-junction photosensitive device is provided. The method may include fabricating at least two photoactive layers, wherein at least one photoactive layer is fabricated on a transparent substrate, and at least one photoactive layer is fabricated on a reflective substrate, patterning at least one optical filter layer on at least one photoactive layer fabricated on a transparent substrate, and bonding the at least two photoactive layers using cold weld or van der Waals bonding. A multi-junction photosensitive device is also provided. The device may have at least two photoactive layers, and at least one optical filter layer, wherein at least two layers are bonded using cold weld or van der Waals bonding. The optical filter layer may be a Distributed Bragg Reflector.