Chemical Engineering December 2011 - 16

CHEMENTATOR
Optical cavity furnace can boost solar cell efficiency
U
sing an array of lamps inside a highly
reflective chamber, the optical cavity
furnace (OCF) takes advantage of photonics
effects to help manufacture solar
photovoltaic cells with higher efficiency
than those made by conventional rapidthermal-processing
(RTP) methods. In
addition, the OCF can reduce cost and
raise efficiency of the manufacturing
process itself.
Scientists at the U.S. Dept. of EnGolden,
ergy's
National Renewable Energy
Laboratory (NREL;
Colo.;
www.nrel.gov) developed the OCF to
harness the ability of photons to effect
atomic-level changes that are important
to solar-cell process outcomes,
such as avoiding iron and other impurities,
creating junctions and improving
electronic properties. NREL engineer
Bhushan Sopori remarks, " Optics
can make a lot of things happen at
the interfaces in a cell, where, for example,
metal can reflect the light and
speed the diffusion of impurities. " The
photonics effects offered by the OCFbased
manufacturing process could
boost cell efficiency by up to four percentage
points, Sopori adds.
Aside from the photonic effects on the
cells, the OCF allows a lower cost, lowerenergy
process. An OCF costs half or less
than an RTP furnace, and uses half as
much energy. Heat losses are virtually
OIL RECOVERY (Continued from p. 15)
with the solution adhered on the surface
of the steel wires. After photoinitiated,
in-situ radical polymerization
for 90 to 120 min., the PAM hydrogencoated
mesh was obtained.
eliminated with highly insulating and
reflective ceramics on the oven walls. The
visible- and infrared-wavelength light
used in the OCF uniformly heats crystalline
silicon wafers, especially at the
edges, which are prone to heat loss and
cooling, with unparalleled precision.
The NREL team is working with an
industry partner (AOS Solar Inc.; Los
Angeles,
Calif.; www.aossolar.com) to
build a manufacturing-size OCF capable
of processing 1,200 silicon wafers
per hour.
The group says the coated mesh is
easily cleaned for reuse, even high-viscosity
oils are easily washed away. The
meshes retain their underwater superoleophobic
and low-oil adhesion properties
after 50 uses.
A formula
for success.
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Chemical Engineering December 2011

Table of Contents for the Digital Edition of Chemical Engineering December 2011