Bandgap Engineering in High-Efficiency Multijunction Concentrator Cells

Conference · Mon Aug 01 00:00:00 EDT 2005

OSTI ID:15020414

King, R R; Sherif, R A; Kinsey, G S; Kurtz, S; Fetzer, C M; Edmondson, K M; Law, D C; Cotal, H L; Krut, D D; Ermer, J H; Karam, N H

This paper discusses semiconductor device research paths under investigation with the aim of reaching the milestone efficiency of 40%. A cost analysis shows that achieving very high cell efficiencies is crucial for the realization of cost-effective photovoltaics, because of the strongly leveraging effect of efficiency on module packaging and balance-of systems costs. Lattice-matched (LM) GaInP/ GaInAs/ Ge 3-junction cells have achieved the highest independently confirmed efficiency at 175 suns, 25?C, of 37.3% under the standard AM1.5D, low-AOD terrestrial spectrum. Lattice-mismatched, or metamorphic (MM), materials offer still higher potential efficiencies, if the crystal quality can be maintained. Theoretical efficiencies well over 50% are possible for a MM GaInP/ 1.17-eV GaInAs/ Ge 3-junction cell limited by radiative recombination at 500 suns. The bandgap - open circuit voltage offset, (Eg/q) - Voc, is used as a valuable theoretical and experimental tool to characterize multijunction cells with subcell bandgaps ranging from 0.7 to 2.1 eV. Experimental results are presented for prototype 6-junction cells employing an active {approx}1.1-eV dilute nitride GaInNAs subcell, with active-area efficiency greater than 23% and over 5.3 V open-circuit voltage under the 1-sun AM0 space spectrum. Such cell designs have theoretical efficiencies under the terrestrial spectrum at 500 suns concentration exceeding 55% efficiency, even for lattice-matched designs.

• Research Organization: National Renewable Energy Lab. (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC36-99-GO10337
• OSTI ID: 15020414
• Report Number(s): NREL/CP-520-38689; TRN: US200518%%311
• Resource Relation: Conference: NREL/CD-520-38172
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
14 SOLAR ENERGY
36 MATERIALS SCIENCE
CONCENTRATORS
EFFICIENCY
ELECTRICITY
HYDROGEN
NITRIDES
ORGANIC COMPOUNDS
PACKAGING
RECOMBINATION
SEMICONDUCTOR DEVICES
SOLAR CONCENTRATORS
VOLATILE MATTER
PV
MULTIJUNCTION CONCENTRATOR SOLAR CELLS
PHOTOVOLTAICS
SEMICONDUCTORS
Solar Energy - Photovoltaics