Global energy demand is increasing rapidly in response to
growth in both the existing and the emerging economies of the world;
consequently, there is unprecedented demand for new solar cell technologies that
can provide clean, renewable energy. Thus far, conversion inefficiencies and
high production costs have limited the potential of existing photovoltaic
devices.
As a result, the primary focus of current photovoltaic cell
research is to find new methods and materials to improve device efficiency and
cost. To this end, improving the tunnel junctions incorporated in all
high-efficiency multi-junction cells today is an aspect of photovoltaic cell
technology receiving generous attention from researchers. Tunnel junctions
improve the efficiency of photovoltaic cells. Optimally, tunnel junctions should
have low impedance to current flow and small potential drop across the junction
and should transmit all of the light to the next cell in line; therefore,
reducing the tunnel junction thickness for less absorption and increasing the
bandgap beyond that of the surrounding cell will improve light transmission, and
subsequently, improve efficiency. Still, existing methods for fabricating tunnel
junctions with high efficiency require the use of expensive techniques such as
metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy
(MBE).
Researchers at Arizona State University have developed a
novel method for growing high quality GaN nano- and micro-columns using chemical
vapor deposition (CVD) on gold droplets deposited on fuse silica substrates. The
films are highly luminescent and achieve efficiency comparable to that
previously seen in thin films grown by more expensive techniques like MOCVD and
MBE. These advances may lead to higher efficiency, longer lasting photovoltaic
cells at reduced cost.
Potential Applications
- Optoelectronics
- Electroluminescent Devices (e.g. light emitter diodes,
laser diodes)
- Photovoltaic Devices
Benefits and Advantages
- Provides High Quality GaN, InN, and InGaN Nano- and
Micro-Columns
- High Efficiency
- High Luminescence
- Reduces Manufacturing Costs ? uses chemical vapor
deposition as opposed to more expensive metal-organic chemical vapor
deposition and molecular beam epitaxial manufacturing techniques
- Offers Favorable Perpendicular Column
Growth