Stacked Monolithic Multijunction Solar Cell Emitter Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Monolithic multijunction solar cells face challenges in achieving high efficiency and reducing manufacturing costs, particularly in concentrator systems, where existing designs do not effectively utilize thinner emitter layers to enhance minority charge carrier mobility and reduce series resistance.
Innovation Solution
A stacked monolithic multijunction solar cell design featuring subcells with emitter layers significantly thinner than their base layers, combined with a metamorphic buffer and semiconductor mirrors, to improve charge carrier mobility and reduce series resistance, while allowing for thicker emitter layers in subsequent subcells to enhance absorption and reduce overall cell thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the emitter layer is made thinner than the base layer by a factor of five or ten, then electron mobility as minority charge carriers is improved, but the absorption of light may be reduced
Solution Approach 1:
The solar cell is divided into multiple subcells (first subcell with thin emitter, second and third subcells with thicker emitters) that handle different portions of the solar spectrum. This segmentation allows each subcell to be optimized for its specific function: the first subcell prioritizes electron mobility with a thin emitter, while subsequent subcells compensate for absorption with thicker emitters, resolving the contradiction between speed and energy utilization.
Solution Approach 2:
Different regions of the multijunction solar cell are given different structural qualities. The first subcell has a thin emitter layer optimized for high electron mobility, while the second and third subcells have thicker emitter layers optimized for light absorption. This local differentiation allows each region to optimize for its primary function without compromising the overall system performance.
2Use of energy by moving object
If thicker emitter layers are used in subsequent subcells, then light absorption is enhanced, but series resistance increases
Solution Approach 1:
The solar cell structure segments the emitter layer thickness across different subcells. The first subcell uses a thin emitter to minimize resistance, while subsequent subcells use thicker emitters to maximize absorption. This segmentation allows the system to balance the trade-off between absorption and resistance by distributing different thicknesses across the series-connected subcells.
3Speed
If all emitter layers are made thin to improve electron mobility, then charge carrier mobility increases, but manufacturing precision requirements increase
Solution Approach 1:
Rather than requiring all emitter layers to be uniformly thin (which would demand high manufacturing precision), the invention segments the structure so that only the first subcell has a thin emitter. Subsequent subcells have thicker emitters that are easier to manufacture with standard precision, thereby reducing overall manufacturing complexity while maintaining high charge carrier mobility in the critical first subcell.
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 design significantly increases the efficiency of multijunction solar cells, particularly at higher sunlight concentrations, by improving electron mobility, reducing series resistance, and decreasing manufacturing costs without compromising efficiency, making concentrator systems more competitive.
Implementation Method 1
the electrons have a higher mobility as minority charge carriers in the base than do the holes as minority charge carriers in the emitter layer
Implementation Method 2
Monolithic multijunction solar cells made of III-V semiconductor material demonstrate particularly high efficiencies for terrestrial applications in the field of concentrator systems
Data Source
AI summary
A stacked monolithic multijunction solar cell, which includes a first subcell having a p-n junction with an emitter layer and a base layer, the thickness of the emitter layer being less than the thickness of the base layer at least by a factor of ten, and the first subcell comprising a substrate having a semiconductor material from the groups III and V or a substrate from the group IV, and which further includes a second subcell arranged on the first subcell and a third subcell arranged on the second subcell, the two subcells each including an emitter layer and a base layer, and a tunnel diode and a back side field layer each being formed between the subcells, the thickness of the emitter layer being greater than the thickness of the base layer in each case between the second subcell and in the third subcell.