AlGaAs Multi-junction Laser PV Cell for 808 nm Efficiency
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Solution Overview
Problem
Existing multi-junction tandem laser photovoltaic cells using GaAs as the absorbing layer suffer from thermal relaxation losses when converting laser energy of 808 nm, resulting in reduced output electrical energy due to photon energy exceeding the band gap, leading to inefficiencies in energy conversion.
Innovation Solution
A multi-junction tandem laser photovoltaic cell design utilizing AlGaAs as the absorbing layer, with carefully adjusted compositions to match the wavelength of incident laser energy, minimizing thermal relaxation losses and enhancing open circuit voltage, and a manufacturing method involving stacked AlGaAs PN-junction sub-cells connected via tunneling junctions, ensuring optimal energy absorption and conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If GaAs is used as the absorbing layer to convert laser energy of 808 nm, then the cell can convert laser energy into electrical energy, but thermal relaxation losses occur because photon energy exceeds the band gap, reducing conversion efficiency
Solution Approach 1:
The patent changes the material parameter by replacing GaAs with AlGaAs alloy, specifically adjusting the aluminum composition ratio to match the band gap energy to the photon energy of 808 nm laser. This parameter optimization minimizes thermal relaxation loss and maximizes conversion efficiency.
Solution Approach 2:
The patent uses AlGaAs composite material which combines aluminum and gallium arsenide in specific ratios to achieve optimal band gap matching for 808 nm laser wavelength, thereby reducing energy loss and improving overall conversion efficiency compared to pure GaAs.
2Power
If multiple sub-cells are stacked to increase output voltage, then higher voltage is achieved, but device complexity increases due to multiple tunneling junctions and series connections
Solution Approach 1:
The patent divides the photovoltaic cell into multiple sub-cells (first sub-cell, second sub-cell, third sub-cell) with distinct functions: light absorption, tunneling connection, and voltage accumulation. This segmentation allows achieving high output voltage through series connection while maintaining clear functional separation and manageable structural complexity.
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 AlGaAs absorbing layer significantly improves conversion efficiency by minimizing thermal relaxation losses, achieving an 8% higher efficiency compared to GaAs-based cells for laser energy of 808 nm, maximizing output voltage and photocurrent production.
Implementation Method 1
A light absorbing layer in the AlGaAs PN-junction sub-cells comprises a P-type Al x1 Ga 1-x1 As base region and an N-type Al x1 Ga 1-x1 As emitter region, wherein the x1 has such a value that the incident laser has a wavelength less than or equal to the absorption long wavelength limit of Al x1 Ga 1-x1 As.
Implementation Method 2
two adjacent sub-cells are connected in series via a tunneling junction
Data Source
Figure 1
Figure 2~3
AI summary
The present application discloses a multi-junction tandem laser photovoltaic cell, comprising a photovoltaic cell stack and a bottom electrode and a top electrode electrically connected to a bottom and a top of the photovoltaic cell stack, respectively, wherein the photovoltaic cell stack comprises stacked N AIGaAs PN-junction sub-cells, and adjacent sub-cells are connected in series via a tunneling junction, in which N≥2. The AIGaAs PN-junction sub-cells use an AIGaAs absorbing layer. The present application further discloses a method of making the multi-junction tandem laser photovoltaic cell. The present application uses AIGaAs as the absorbing layer of the multi-junction tandem cell to convert laser energy, which can effectively increase the open circuit voltage of the photovoltaic cell, thereby significantly improving the conversion efficiency of the photovoltaic cell.