26. 1% solar cell efficiency for Ge mechanically stacked under GaAs

Journal Article · Thu Oct 01 00:00:00 EDT 1987 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.339389· OSTI ID:6052035

Partain, L D; Kuryla, M S; Weiss, R E; Ransom, R A; McLeod, P S; Fraas, L M; Cape, J A

We have processed a diffused Ge wafer into a Ge concentrator solar cell and mechanically stacked it under a GaAs cell fabricated by Varian. We measured this stack's efficiency to be 26.1% for terrestrial air mass 1.5 direct (AM1.5D) conditions at a 285 x concentration ratio. We showed that this efficiency is limited by optical absorption in the Varian GaAs cell caused by high 2--4 (10/sup 18/) cm/sup -3/ substrate doping. We used a 2 x 10/sup 17/ cm/sup -3/ doped GaAs filter to estimate the stack efficiency as 27.4%, which would be achieved with the same Varian GaAs cell formed on a lower doped substrate. We project efficiencies assuming the best properties reported for a GaAs device. This gives a 29.6% efficiency for an improved, planar Ge cell and 31.6% efficiency for a proposed point contact geometry for the Ge cell. The corresponding space (AM0) efficiencies at a 159 x concentration ratio range from the 23.4% value we measured on the stack up to 28.4% projected for the point contact Ge place under the best GaAs cell. We showed that Ge cells give higher efficiencies than Si when stacked under GaAs.

• Research Organization: Chevron Research Co., Richmond, California 94802
• OSTI ID: 6052035
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 62:7; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
ARSENIC COMPOUNDS
ARSENIDES
CRYSTAL DOPING
DATA
DIRECT ENERGY CONVERTERS
EFFICIENCY
ELEMENTS
EQUIPMENT
EXPERIMENTAL DATA
FABRICATION
GALLIUM ARSENIDE SOLAR CELLS
GALLIUM ARSENIDES
GALLIUM COMPOUNDS
GERMANIUM
INFORMATION
METALS
NUMERICAL DATA
OPACITY
OPTICAL PROPERTIES
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
PNICTIDES
SOLAR CELLS
SOLAR EQUIPMENT