4 June 2022 | New Scientist | 15Materials
Alex Wilkins
THE chemical that makes tomatoes
red could also boost the efficiency
and stability of solar panels.
Most commercial solar cells are
silicon-based, but a new generation
of solar cells made from thin films of
perovskite, a titanium and calcium
crystal, promise greater efficiencies
and are easier to work with. Yet
perovskites degrade far faster than
silicon-based cells, so improvements
in stability are highly sought after.
Donglei Zhou at Jilin University
in China and his colleagues chose
to add lycopene, a pigment found
in tomatoes and other red fruit
and vegetables, to perovskite cells
because they thought its powerful
antioxidant properties might help
slow degradation. The modified
solar cells became more stable,
losing about 8 per cent efficiency
after 3500 hours, which is about six
times better than standard devices,
and were 3 percentage points more
efficient at converting light to power.
“When UV is shone on human
skin, [dietary] lycopene binds to
free radicals produced by ultraviolet
light to protect skin tissue from
damage,” says Zhou. “Therefore,
we were curious whether lycopene
has a similar effect on perovskite
solar cells when exposed to
ultraviolet and oxygen.”
Zhou and his team think that, as
well as binding with the perovskite
to cut the amount of oxidation, the
lycopene also improves efficiency
by helping to reduce the number of
microscopic grains in the perovskite’s
crystal structure, which improves
the flow of electricity (Advanced
Energy Materials, doi.org/gp7bcd).
A 3 percentage point increase
in power conversion efficiency is
pretty impressive, says Kyle Frohna
at the University of Cambridge.
“The devices they make in the
end aren’t the absolute best in the
world, but the relative improvements
from their control devices are pretty
promising,” he says. ❚
Dash of tomato
colouring makes
better solar panels
A NEW UK visa aimed at
attracting the best graduates
from across the world risks
excluding talent from African
countries, scientists and
policy-makers have warned.
The High Potential Individual
visa, launched by the UK Home
Office on 30 May, is aimed at
people who have graduated
in the past five years from one
of what are often regarded as
the world’s top universities.
People with a recent
undergraduate degree or PhD
from such a university will be
able to move to the UK for up to
three years without needing to
have a job lined up. Typical UK
visas for foreign researchers
require a pre-existing job offer,
a fellowship, certain research
grants or that the individual
is a notable prize-winner.
The Home Office has drawn
up a list of foreign universities
it considers to be the best in the
world by compiling institutions
that appear in the top 50 at least
twice across three specified
global university league tables.The list includes no universities
in African nations, effectively
excluding anyone who has
studied in Africa from the visa.
There are also no universities
in Central and South America
or South Asia on the list.
“These ratings are based on
criteria that favour universities
which have been around for
hundreds of years and have
access to a lot of funding,” says
Amina Ahmed El-Imam at the
University of Ilorin in Nigeria.
“As someone from Nigeria
who did their PhD in Britain,it’s heartbreaking to see that
there are still processes being
put in place that inadvertently
exclude Africans. Does this
visa mean that there are no
individual graduates from
African universities with
high potential?”
“I think this is a deeply
inequitable approach,” says
Christopher Trisos at the
University of Cape Town in
South Africa. “The exclusion ofAfrican universities strikes out
many graduates with in-depth
knowledge of major challenges
facing humanity this century,
such as climate change, food
security and expanding access
to technology.”
If UK firms and government
want to play a role in solving
these challenges, they need to
recognise the diverse skill sets
held by many graduates from
universities in low-income
countries, he says.
Global university league
tables have previously been
criticised as a flawed way of
measuring academic excellence.
“There is a wealth of evidence
across social sciences that
rankings produce a skewed idea
of what constitutes quality in
higher education and science,
especially on a global scale,” says
Jelena Brankovic at Bielefeld
University in Germany. “Making
a new ranking by combining
existing rankings does nothing
else but create an illusion of
an added layer of objectivity.”
“I’m sceptical about it
because ‘top’ universities
and the best universities
are not the same when it
comes to teaching quality,”
says Nick Hillman at the Higher
Education Policy Institute in
Oxford, UK.
The Home Office didn’t
respond to specific questions
about why the visa relies on
a potentially flawed league
table system or why it excludes
graduates from African
universities. “The new High
Potential Individual route will
make it as simple as possible
for internationally mobile
individuals at an early stage of
their careers who demonstrate
high potential to come to
the UK,” says Home Office
LU minister Kevin Foster. ❚IS^ ALVARE
Z/GET
TY
IMAGESScientists working
in a medical research
laboratoryScience policyJason Arunn MurugesuUK talent visa blocks graduates
from African universities
“ Does this visa mean that
there are no graduates
from African universities
with high potential?”