Multijunction Solar Cell With Patterned Emitter Reducing Recombination
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Solution Overview
Problem
Conventional multijunction solar cells with unpatterned emitters suffer from reduced efficiency due to non-ideal pathways for photogenerated carriers, leading to increased recombination losses.
Innovation Solution
A multijunction solar cell design featuring a patterned emitter with well regions doped with a second carrier type on a Group IV semiconductor base substrate, reducing the emitter's surface area and volume, and forming additional solar subcells over the first subcell to enhance carrier collection and reduce recombination losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an unpatterned emitter is used in a multijunction solar cell, then the manufacturing process is simple, but the efficiency is reduced due to increased recombination losses
Solution Approach 1:
The emitter is segmented into discrete patterned regions rather than a continuous unpatterned layer. This segmentation reduces the total emitter area and volume, creating non-ideal pathways for photogenerated carriers that minimize recombination losses while maintaining manufacturability through standard diffusion processes
Solution Approach 2:
The emitter is designed with non-uniform local properties through patterning, creating regions of different dopant concentrations and geometries. This local quality variation optimizes carrier collection in different areas, reducing overall recombination losses while maintaining ease of manufacture through selective diffusion masking
2Loss of energy
If the emitter surface area is reduced through patterning, then recombination losses are reduced, but the carrier collection area is decreased
Solution Approach 1:
The emitter pattern extends into the vertical dimension with varying depths and profiles, compensating for the reduced horizontal surface area. This dimensional transition allows sufficient carrier collection area to be maintained through increased vertical presence while keeping the horizontal footprint small to reduce recombination losses
3Loss of energy
If a patterned emitter is implemented, then Shockley-Read-Hall recombination losses are reduced, but the manufacturing complexity increases
Solution Approach 1:
The patterning mask is prepared and positioned before the diffusion process, establishing the emitter pattern in advance. This preliminary action allows the complex patterned emitter structure to be formed through a single diffusion step, reducing manufacturing complexity while achieving reduced Shockley-Read-Hall recombination losses
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 patterned emitter design reduces Shockley-Read-Hall recombination losses, resulting in improved solar cell efficiency by optimizing carrier collection and reducing series resistance, thereby increasing the conversion of sunlight to power.
Implementation Method 1
A patterned emitter is formed at a first surface of the base substrate. The patterned emitter comprises a plurality of well regions doped with a dopant of a second carrier type in the Group IV semiconductor. The base substrate including the patterned emitter form a first solar subcell.
Implementation Method 2
A patterned emitter is formed at a first surface of the base substrate. The patterned emitter comprises a plurality of well regions doped with a dopant of a second carrier type in the Group IV semiconductor.
Data Source
AI summary
A multijunction solar cell includes a base substrate comprising a Group IV semiconductor and a dopant of a first carrier type. A patterned emitter is formed at a first surface of the base substrate. The patterned emitter comprises a plurality of well regions doped with a dopant of a second carrier type in the Group IV semiconductor. The base substrate including the patterned emitter form a first solar subcell. The multijunction solar cell further comprises an upper structure comprising one or more additional solar subcells over the first solar subcell. Methods of making a multijunction solar cell are also described.