Lanthanide-Sensitized Oxides Upconvert Infrared Photons for Solar Cells
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Solution Overview
Problem
Silicon-based solar cells are limited in their ability to utilize approximately 30% of the sun's radiation due to the Shockley-Queisser limit, as they cannot absorb light with wavelengths longer than 1100 nm, which is referred to as infrared light, due to their intrinsic optical band-gap of 1.1 eV.
Innovation Solution
Development of doped oxides with a host oxide and a lanthanide dopant, such as Yb3+, which absorb infrared light and transfer its energy to the oxide matrix through lattice vibrations, upconverting it into visible light, thereby overcoming the Shockley-Queisser limit by converting nearly 10% of incident infrared photons into visible photons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If silicon-based solar cells are used, then photovoltaic energy conversion can occur, but light with wavelength longer than 1100 nm cannot be absorbed due to the Shockley-Queisser limit
Solution Approach 1:
The patent introduces upconversion materials as an intermediary substance between the sunlight and silicon-based solar cells. These materials absorb infrared light (wavelength > 1100 nm) that cannot be directly absorbed by silicon, convert it to visible light through upconversion, and then the converted light can be absorbed by the solar cell to generate electricity. This mediator enables the system to utilize a broader spectrum of sunlight.
Solution Approach 2:
The invention changes the energy parameter of photons by using upconversion materials to convert low-energy infrared photons into high-energy visible photons. This parameter transformation allows the solar cell system to access and utilize infrared portion of the solar spectrum that would otherwise be inaccessible due to silicon's bandgap limitations.
2Adaptability or versatility
If rare earth ion co-doped NaYF4 particles are used for upconversion, then infrared light can be converted to visible light, but the quantum yield is low (0.005% to 0.3%)
Solution Approach 1:
The patent modifies the physical and chemical parameters of the upconversion material system by using alternative host matrices, dopant combinations, particle size optimization, and surface treatments to enhance the quantum yield of infrared to visible light conversion, thereby reducing energy loss while maintaining conversion capability.
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 doped oxides achieve a higher infrared to visible light upconversion efficiency compared to existing materials like rare earth ion co-doped NaYF4 particles, potentially increasing photovoltaic energy generation efficiency by approximately 1.8% when integrated into solar cells.
Implementation Method 1
Materials that convert low-energy photons, e.g., infrared light, into high-energy photons, e.g., visible light, are referred to as upconversion materials
Implementation Method 2
absorb infrared light and transfer its energy to the oxide matrix through lattice vibrations, upconverting it into visible light
Implementation Method 3
directing infrared radiation onto a doped oxide described above to stimulate the dopant and thereby generate white light
Data Source
AI summary
The present invention includes upconversion materials such as lanthanide-sensitized oxides that are useful for converting low-energy photons into high-energy photons. Because silicon-based solar cells have an intrinsic optical band-gap of 1.1 eV, low-energy photons having a wavelength longer than 1100 nm, e.g., infrared photons, cannot be absorbed by the solar cell and used for photovoltaic energy conversion. Only those photons that have an energy equal to or greater than the solar cell's band gap, e.g., visible photons, can be absorbed and used for photovoltaic energy conversion. The oxides described herein transform photons having an energy less than the energy of a solar cell's band gap into photons having an energy equal to or greater than the energy of the band gap. When these oxides are incorporated into a solar cell, they provide more photons for photovoltaic energy conversion than otherwise would be available in their absence. Nearly 10% of the infrared photons incident on these oxides are upconverted into visible photons. This upconversion efficiency is more than twice as large as the upconversion efficiency for NaYF4-based upconversion materials. The solar radiation energy conversion efficiency of a silicon-based solar cell will increase by 1.8% or greater by including the oxides described herein because they allow the solar cell to absorb and use are larger portion of the solar spectrum for photovoltaic energy conversion.