Improved epilayer qualities and electrical characteristics for GaInN multiple-quantum-well photovoltaic cells and their operation under artificial sunlight and monochromatic light illuminations

• Published in: AIP advances Vol. 11; no. 9; pp. 095208 - 095208-8
• Main Authors: Miyoshi, Makoto, Nakabayashi, Taiki, Yamamoto, Kosuke, Dalapati, Pradip, Egawa, Takashi
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.09.2021; AIP Publishing LLC
• Subjects: Carrier recombination; Current carriers; Energy conversion efficiency; Illumination; Metalorganic chemical vapor deposition; Open circuit voltage; Photovoltaic cells; Quantum wells; Sapphire; Solar cells; Wireless power transmission
• ISSN: 2158-3226; 2158-3226
• DOI: 10.1063/5.0062346

GaInN-based photovoltaic (PV) devices are highly promising for application to optical wireless power transmission (OWPT) systems as well as solar cells. This paper reports the research results of Ga0.9In0.1N multiple-quantum-well (MQW) PV cells on sapphire, focusing primarily on the growth temperature managements in metalorganic chemical vapor deposition (MOCVD) processes. As a result of the MOCVD study, the epilayer qualities in the PV cell structures improved significantly through the adoption of an optimized growth temperature for the GaInN MQWs and the two-step growth for the top p-GaN layers. Furthermore, the improved epilayer qualities resulted in the decrease in carrier recombination currents and series resistance for the forward diode characteristics without a light illumination. Subsequently, a sample with the improved qualities exhibited a higher open-circuit voltage and a higher fill factor in the PV characteristics. Eventually, the highest power conversion efficiency (PCE) in this study was measured to be 1.6% at a 1-sun solar spectrum and 42.7% at a monochromatic light illumination with 389 nm in wavelength and 5 mW cm−2 in optical power density. The dependency of the PV performance on the optical power densities at a monochromatic light illumination predicted that a higher PCE value may be achievable at a higher optical-power-density illumination. This is a very promising prediction when considering the practical application to OWPT systems.