Researchers have integrated A3B5semiconductors on a silicon substrate in a prototype solar cell and claim thetechnique could enable the production of III-V solar cells with conversionefficiencies of around 40%.
Researchers at Russia’s ITMO University, inSt Petersburg, are testing compound A3B5 semiconductors in the manufacture ofmulti-junction, III-V solar cells.
A3B5 materials are a family ofsemiconductors including gallium arsenide (GaAs), indium arsenide (InAs),gallium phosphide (GaP), indium phosphide (InP), gallium antimonide (GaSb) andindium antimonide (InSb) which are used as basic materials for electronic andoptoelectronic applications.
The ITMO University team say theyfabricated the top layer of a small, laboratory prototype solar cell whichfeatured A3B5 materials integrated on a silicon-substrate for the first time.They claim the innovation could lead to highly efficient solar cells atconsiderably lower costs, as the silicon substrate used in their device wasmuch less expensive than materials used in IIV-V solar cells – so named afterthe groups of the periodic table the elements concerned occupy.
Perfect match
The researchers said theepitaxial-synthesis-on-silicon-substrate is a difficult manufacturing processas the deposited semiconductor must have the same crystal lattice parameter assilicon. “Roughly speaking, the atoms of this material should be at the samedistance from each other as are the silicon atoms,” they said.
GaP is one semiconductor meeting thoserequirements but the researchers said its light trapping properties arelimited. The gallium phosphide compound, however, when combined with nitrogen,shows direct-band property and strong light-trapping properties as well asbeing suitable for integration on the silicon substrate. “At the same time,silicon doesn’t just serve as the building material for the photovoltaic layers– it itself can act as one of the photo-active layers of a solar cell,absorbing light in the infrared range,” the ITMO University team said.
Adding layers
The scientists said the efficiency of theirsolar cell rises as extra photo-active layers are added, and they claim theA3B5 semiconductor can also be used for intermediate layers. They believe thepotential efficiency of such solar cells could top 40% if used withconcentrating PV technology.
The findings were presented in the paperGaNP-based photovoltaic device integrated on Si substrate, published in SolarEnergy Materials and Solar Cells, and on the ScienceDirect website.
Gallium arsenide and other III-V materialsare among the best known in terms of efficiency potential for solar cells butcost has thus far limited them to niche applications such as poweringsatellites and drones.
(Source: PV-magazine)
