Quantum Dot Up-Converter Layer for Photovoltaic Efficiency
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Solution Overview
Problem
Conventional photovoltaic devices have limited efficiency due to the underutilization of the solar spectrum, as they can only convert a fraction of incident light energy, leading to thermalization losses and inefficiencies in energy conversion.
Innovation Solution
A photovoltaic device incorporating a quantum dot absorber layer and a quantum dot up-converter layer, where the up-converter layer enhances energy conversion by emitting low-energy light back to the absorber, allowing for increased energy absorption and potentially higher efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single bandgap absorber material is used, then the device structure is simple, but only a fraction of the solar spectrum is utilized and thermalization losses occur
Solution Approach 1:
The absorber is segmented into multiple quantum dot layers with different bandgaps (first quantum dot layer with bandgap E1, second quantum dot layer with bandgap E2 where E1 < E2). This segmentation allows different portions of the solar spectrum to be absorbed by different layers, reducing thermalization losses and improving overall energy conversion efficiency.
Solution Approach 2:
The device uses composite quantum dot structures where quantum dots of different materials and bandgaps are integrated within the absorber. The first quantum dot layer contains quantum dots with smaller bandgap, while the second quantum dot layer contains quantum dots with larger bandgap, creating a composite material system that captures a broader spectrum.
2Productivity
If quantum dot layers with different bandgaps are used, then the solar spectrum utilization is improved, but the device complexity increases
Solution Approach 1:
Multiple quantum dot layers with different bandgaps are merged into a single absorber structure. The first quantum dot layer and second quantum dot layer are positioned adjacent to each other within the same absorber, combining their spectral absorption capabilities while maintaining a relatively integrated device architecture.
3Productivity
If Erbium doped NaYF4 is used as up-converting material, then the up-conversion function is achieved, but the quantum efficiency is very poor
Solution Approach 1:
The patent changes the material parameters by replacing Erbium doped NaYF4 with quantum dot materials that have superior quantum efficiency for up-conversion. The quantum dot up-converter layer uses quantum dots with specific size and material composition optimized for high-efficiency photon up-conversion, fundamentally improving the energy conversion parameter.
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 quantum dot up-conversion process increases the conversion efficiency by allowing the absorber to utilize previously lost low-energy light, potentially reaching theoretical limits beyond 47.6% efficiency.
Implementation Method 1
In the up-converter, the photons are absorbed in two or more steps. After excitation, the electron-hole pairs recombine radiatively in one step, whereby they emit light of correspondingly higher energy.
Implementation Method 2
After excitation, the electron-hole pairs recombine radiatively in one step, whereby they emit light of correspondingly higher energy.
Implementation Method 3
Photovoltaic devices, also referred to as solar cells, convert light directly into electricity.
Implementation Method 4
When light (i.e., photons) hits the device, some of the photons are absorbed in the region of the junction, freeing electrons and holes (i.e., carriers) in the absorber.
Implementation Method 5
The interface, or junction, between these two layers contains an electric field. If the photons have enough energy, the carriers will be driven out by the electric field and move through the silicon and into an external circuit.
Data Source
AI summary
A photovoltaic apparatus includes an absorber including a first quantum dot layer having a first plurality of quantum dots of a first quantum dot material in a first matrix material, and an up-converter layer positioned adjacent to the absorber layer, the up-converter layer including a second quantum dot layer having a second plurality of quantum dots of a second quantum dot material and a second matrix material.