Growth and Characterization of Tandem-Junction Photovoltaic Nanowires
Author
Summary, in English
In this thesis, nanowires for photovoltaic applications are studied. Nanowire solar cells have the potential to reach the same efficiencies as the world-record III–V solar cells while only using a fraction of the material. First, InP single-junction nanowires were investigated. For solar energy harvesting, large-area nanowire solar cells have to be processed but so far only devices with less than one mm2 have been fabricated. To lay the foundation of large-area nanowire solar cells, the wafer-scale synthesis of InP nanowire arrays was systematically studied. Then the effect of embedding InP nanowires in different oxides was investigated. Due to their inherent large surface-to-volume ratio, nanowires require surface passivation. However, fixed charge carriers in the passivating layer can alter the electrostatic potential of nanowires, which was directly imaged by measuring the electron-beam-induced current. Furthermore, the current-voltage characteristics of single nanowires under in situ illumination was measured and correlated with electron-beam-induced current measurements, by using a setup that combines a nanoprobe system with an optical fiber coupled to a multi-LED setup inside a scanning electron microscope.
Guided by the multi-LED and electron-beam-induced current setup, tandem-junction nanowires were developed. After identifying and subsequently preventing the occurrence of a parasitic junction when combining an InP n–i–p junction with a tunnel diode, GaInP/InP tandem-junction nanowires were synthesized. An optical and electrical bias was applied to individually measure the electron-beam-induced current of both sub-cells. Finally, axially defined, GaInP/InP/InAsP triple-junction photovoltaic nanowires optimized for light absorption exhibiting an open-circuit voltage of up to 2.37 V were synthesized. The open-circuit voltage amounts to 94 % of the sum of the respective single-junction nanowires. These results pave the way for realizing the next-generation of scalable, high-performance, and ultra-high power-to-weight ratio multi-junction, nanowire-based solar cells.
Publishing year
2022
Language
English
Full text
Document type
Dissertation
Publisher
Solid State Physics, Lund University
Topic
- Condensed Matter Physics
- Nano Technology
Keywords
- III–V semiconductors
- nanowire
- photovoltaics
- tandem junction
- MOVPE
- EBIC
- Fysicumarkivet A:2022:Hrachowina
Status
Published
ISBN/ISSN/Other
- ISBN: 978-91-8039-210-5
- ISBN: 978-91-8039-209-9
Defence date
25 May 2022
Defence time
13:15
Defence place
Lecture Hall Rydbergsalen, Department of Physics, Sölvegatan 14, Faculty of Engineering LTH, Lund University, Lund.
Opponent
- Esther Alarcón Lladó (Dr.)