Alexandria Digital Research Library

Two-Terminal Bonded III-V Multijunction Photovoltaic Devices

Lin, Chieh-Ting
Degree Grantor:
University of California, Santa Barbara. Electrical and Computer Engineering
Degree Supervisor:
John E. Bowers
Place of Publication:
[Santa Barbara, Calif.]
University of California, Santa Barbara
Creation Date:
Issued Date:
Nanotechnology, Energy, and Engineering, Electronics and Electrical
Device Bonding
Solar Cell
Dissertations, Academic and Online resources
Ph.D.--University of California, Santa Barbara, 2013

Multi-junction solar cells combine multiple junctions made of materials with different band gaps that are carefully selected to optimize power conversion efficiency. Current state of the art triple-junction devices achieve power conversion efficiencies over 40% under concentrated sunlight. As the industry drives for higher efficiency with additional junctions, lattice matching becomes a limiting factor due to specific band gap requirements for each junction. This work describes a bonding method that was developed to enable the creation of multi-junction cells using sub-cells, which cannot be grown monolithically due to lattice constant constrains.

A four-junction (4J) configuration is proposed in which an upper GaInP/GaAs 2J tandem cell is bonded to a lower GaInAsP/GaInAs 2J tandem cell. In this 4J configuration, the upper tandem is grown inverted and lattice-matched to a GaAs substrate and the lower tandem is grown upright and lattice-matched to an InP substrate. A five-junction (5J) configuration with a GaN-based wide-band gap material integrated with the four-junction structure described above is also possible, and the expected efficiency for this 5J device exceeds 50%. A wide variety of other device configurations using similar bonding methods can be explored. Devices have been fabricated using Au-Au bonded interconnects and either SiO2 or GaInP2 as a transparent filler for the remainder of the interfacial volume. Several different sub-cell configurations have been successfully fabricated, using both SiO2 and GaInP 2 fillers. So far, the most complex configuration fabricated is a GaInP/GaAs two-junction cell bonded to an InGaAs cell using a GaInP2 optical coupling layer. This configuration results in Voc= 2.70 V, J sc = 12.66 mA/cm2, FF = 83.0%, and efficiency =28.39% under the 1-sun ASTM G173 direct spectrum.

This dissertation will discuss the design of the bonded III-V multi-junction device, such as band gap selection, metal topology design and optical design. The fabrication development process is also discussed and both device characterization and results will be presented.

Physical Description:
1 online resource (178 pages)
UCSB electronic theses and dissertations
Catalog System Number:
Inc.icon only.dark In Copyright
Copyright Holder:
Chieh-Ting Lin
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