Multijunction Solar Cell Layers for Better Current Collection
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Solution Overview
Problem
Multijunction solar cells face challenges in achieving optimal combinations of subcell bandgaps and wavelength response ranges to maximize efficiency, particularly due to limitations in semiconductor materials with favorable minority-carrier properties and lattice matching, leading to reduced current collection and efficiency.
Innovation Solution
Incorporating low-bandgap absorber regions (LBARs) and improved transport layers in the quasi-neutral regions of solar cells, which can have lower bandgaps than adjacent layers and improve minority-carrier transport properties, allowing for increased photogenerated current density and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple subcells with different bandgaps are stacked to increase power output, then energy conversion efficiency is improved, but device complexity increases
Solution Approach 1:
The solar cell is divided into multiple subcells with different bandgaps stacked in series, where each subcell absorbs a specific portion of the solar spectrum. This segmentation allows the device to convert different wavelengths of light into electrical energy simultaneously, thereby increasing overall energy conversion efficiency while managing complexity through functional division
Solution Approach 2:
Each subcell is designed with specific local properties (bandgap energy, thickness, material composition) optimized for absorbing particular wavelength ranges of sunlight. The top subcell has a wider bandgap for high-energy photons, while lower subcells have narrower bandgaps for lower-energy photons, creating a gradient structure that maximizes spectral utilization
2Reliability
If semiconductor materials with favorable minority-carrier properties are used, then current collection is improved, but adaptability in bandgap combinations is limited
Solution Approach 1:
The invention employs metamorphic buffer layers and graded composition structures that allow continuous adjustment of lattice constants and bandgaps across different subcells. By varying the composition ratios of alloy semiconductors (e.g., AlGaInP, GaInAs), the device achieves optimal bandgap combinations for each subcell while maintaining lattice matching through intermediate buffer layers, thus enabling both high current collection and spectral adaptability
Solution Approach 2:
Metamorphic buffer layers serve as intermediary structures between subcells with different lattice constants. These buffer layers gradually transition the crystal lattice from one composition to another, reducing dislocation density and enabling the stacking of subcells with widely different bandgaps while maintaining high material quality and current collection efficiency
3Productivity
If subcell layer bandgaps are optimized for maximum efficiency, then wavelength response ranges are improved, but manufacturing precision requirements increase
Solution Approach 1:
The invention uses compositional grading and metamorphic buffer layers to achieve precise control over bandgap parameters in each subcell. By gradually varying the alloy composition during epitaxial growth, the device achieves optimal bandgap values for maximum spectral utilization while maintaining lattice matching, thereby reducing dislocation density and simplifying manufacturing tolerances
Solution Approach 2:
Metamorphic buffer layers are grown in advance between subcells to pre-establish the appropriate lattice constant and reduce thermal stress before the actual active layers are deposited. This preliminary action prevents dislocation propagation and ensures high material quality in the subsequent subcell growth, reducing the need for post-manufacturing adjustments
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 use of LBARs and improved transport layers enhances photogenerated current density, voltage, and energy conversion efficiency by optimizing bandgap combinations and wavelength response, enabling better energy conversion and current collection in multijunction solar cells.
Implementation Method 1
A photovoltaic device or solar cell is a device that is capable of converting sunlight to electrical energy by the photovoltaic effect
Implementation Method 2
low-bandgap absorber regions (LBARs) and improved transport layers in the quasi-neutral regions of solar cells, which can have lower bandgaps than adjacent layers and improve minority-carrier transport properties, allowing for increased photogenerated current density
Data Source
AI summary
In one aspect, optoelectronic devices are described herein. In some implementations, an optoelectronic device comprises a photovoltaic cell. The photovoltaic cell comprises a space-charge region, a quasi-neutral region, and a low bandgap absorber region (LBAR) layer or an improved transport (IT) layer at least partially positioned in the quasi-neutral region of the cell.