POWER December 2021 - 19

SOLAR POWER
indirect experimentation and theory, that
the problem decreases when less boron
is used or when less oxygen is present
in the silicon.
The collaboration between NREL and
Mines, with research funded by the Solar
Energy Technologies Office within the
DOE, relied on electron paramagnetic
resonance (EPR) to identify defects responsible
for the LID. The microscopic
examination revealed a distinct defect
signature as the sample solar cells became
more degraded by light. The defect
signature disappeared when the
scientists applied the empirical " regeneration "
process to cure the LID that
industry has adopted. The researchers
also found a second, " broad " EPR signature
affected by light exposure, involving
many more dopant atoms than there
are LID defects. They hypothesized that
not all atomic changes induced by light
lead to the LID. The researchers said the
techniques developed to study LID can
be extended to reveal other types of degrading
defects in silicon solar cells, and
also in other semiconductor materials
used in photovoltaics including cadmium
telluride and perovskites.
Maximizing Panel Efficiency
Solar cell and module developers continue
to look for ways to maximize photovoltaic
(PV) panel efficiency. JinkoSolar
and LONGi, two Chinese manufacturers,
have surpassed solar conversion efficiencies
of 25% for their crystalline silicon
technologies. Australian researchers
have developed a bifacial silicon solar cell
with an efficiency of 24.3% on the front
and 23.4% on the rear, for an effective
output of about 29%. UK-based Oxford
PV this past year announced a new efficiency
record for its perovskite solar
cells at 29.52%. Oxford PV completed
construction of the manufacturing site
for its perovskite-on-silicon tandem solar
cells in July, and expects to begin full
commercial production in 2022.
Solliance Solar Research, a consortium
based in the Netherlands, in late
October said researchers from three of
its partners had achieved a 29.2% power
conversion efficiency on a transparent
bifacial perovskite solar cell combined
with a crystalline silicon solar cell in a
four-terminal tandem configuration. The
group said the cell is based on a highly
near-infrared transparent perovskite cell
built by the Netherlands Organisation
for Applied Scientific Research (better
known as TNO) and Belgian laboratory
December 2021 | POWER
1. Solar FlexRack has installed its solar tracking systems at projects across California, including
at agricultural sites, such as this installation at the Danell Brothers Dairy. Courtesy:
Solar FlexRack
EnergyVille, along with an 11.4%-efficient
c-Si interdigitated back contact
silicon heterojunction cell developed by
Panasonic. EnergyVille has touted its
work on tandem configurations, saying,
" By combining two (or more) different
solar cells with carefully selected material
properties on top of each other in
so-called tandem configuration, we can
convert a wider part of the light spectrum
into electrical energy. In this way
we surpass the physical limitations of
single solar cells. " That is, by combining
a perovskite top cell on a silicon bottom
cell, EnergyVille is aiming at +30% tandem
energy conversion efficiency, which
is larger than the theoretical maximum
of silicon solar cells of about 28%.
Crystalline silicon technology accounts
for the vast majority of the solar
power market. In the U.S., though, supply
chain issues and trade restrictions on
imports from China-including concerns
about the production of polysilicon in
Xinjiang-have opened doors for thinfilm
producers. Arizona-based First Solar,
which produces cadmium-telluride
(CdTe) solar modules and panels, this
summer said it is investing nearly $700
million to build a third U.S. manufacturing
plant, which will expand its domestic
production capacity by 3.3 GW. The company
also announced construction of a
similar 3.3-GW plant in India.
Chinese manufacturer China National
Building Materials, which produces thinfilm
copper indium gallium diselenide
panels, recently said it was expanding its
production, adding about 1 GW of capacity
for CdTe modules.
New Solar Cells
Sharma told POWER, " The most important
technology development for solar
panels and systems is the emergence
of n-type solar cells. " Sharma said the
two most common n-type solar cells are
TOPCon (passivated contact) and heterojunction.
A hetereojunction solar cell
www.powermag.com
combines two different technologies into
one cell: a crystalline silicon cell set between
two layers of amorphous thin-film
silicon. The technologies used together
allow more energy to be harvested compared
to using either technology alone.
" N-type solar cells are made from a
different chemical composition of wafer, "
said Sharma. " There's going to be a significant
evolution over the next three to
five years of cell manufacturing. What's
predominantly produced now is p-type
mono PERC cells [monocrystalline silicon
cells] ... these will all start migrating to ntype
TOPCon and heterojunction cells. "
Sharma said, " Manufacturing of n-type
cells is not made for a specific niche. It's
not a specific application; these new
cells will improve the efficiency of all solar
panels and all applications. This advancement
is something that will have a
significant impact on the entire industry
and all solar deployments-by improving
the energy efficiency of all different
types of PV panels. "
Solaria is set to launch its new PowerXT
430R-PL (430 watt) solar panel in
March 2022. The panel will be optimized
for next-generation module level power
electronics (MLPE), which are devices
that can be incorporated into a solar
PV system to improve its performance
in certain conditions, such as in shade.
MLPE devices
include
microinverters
and direct-current (DC) power optimizers-all
designed to improve the energy
production of the solar power system.
Tracking the Sun
New racking systems also are increasing
the efficiency of solar arrays. Solar
FlexRack in October announced that its
solar trackers have now been installed in
more than 80 solar projects on California
farms, including at a 2.82-MW project for
Danell Brothers Dairy (Figure 1), south of
Hanford. The array was installed by Renewable
Solar Inc., which installs commercial
and agricultural solar projects in California.
19

http://www.powermag.com

POWER December 2021

Table of Contents for the Digital Edition of POWER December 2021