Nanoscale discovery could push perovskite solar cells to 31% efficency

Researchers from the US Department of Energy’s Lawrence Berkeley National Laboratory have made a discovery within the nanoscale peaks and valleys of perovskite that may allow solar cells utilising the material to reach their theoretical conversion limit of 31%.

Perovskite is a crystalline mineral that has been used to create solar cells that are inexpensive and easy to fabricate, much like organic solar cells (cells which use conductive organic polymers/small organic molecules).

The central point of interest for perovskite cells, however, is that the efficiency at which they convert photons to electricity has increased more rapidly than any other material to date, starting at 3% in 2009 and rising to 22% today. This puts them roughly alongside silicon solar cells (which work by placing a thin film of silicon on top of glass) in terms of efficiency.

However, a new discovery from a team of scientists from the Molecular Foundry and the Joint Center for Artificial Photosynthesis, both at Berkeley Lab, has found that the current composition of perovskite solar cells is not in fact taking advantage of the full possible efficiency.


Using photoconductive atomic force microscopy, which utilizes a conductive tip to scan the material’s surface, the scientists mapped two properties on the active layer of the solar cell that relate to its photovoltaic efficiency.

The maps revealed a bumpy surface composed of grains which are, in themselves, composed of multi-angled facets.

The importance of analysing this structure was revealed in that there is a huge difference in energy conversion efficiency between the facets. While some approach perovskite’s theoretical energy conversion limit of 31%, others immediately adjacent perform incredibly poorly.

“This was a big surprise. It shows, for the first time, that perovskite solar cells exhibit facet-dependent photovoltaic efficiency,” said Weber-Bargioni, corresponding author of the research paper.

Francesca Toma, another of the contributing scientists, added: “These results open the door to exploring new ways to control the development of the material’s facets to dramatically increase efficiency.”

shutterstock_115625674 (1)

The maps of the cell revealed several qualities of the facets and the differences between them, perhaps most notably that facets with high photocurrent generation had high open circuit voltage, and facets with low photocurrent generation had low open circuit voltage.

In action, the facets essentially behave like billions of microscopic solar cells, all connected in parallel. However, while some cells operate at a high efficiency, others work poorly. The difficulty comes from the current flowing towards the bad cells, thus reducing the overall performance.

The research team believes though that it is possible to optimise the material to eliminate the losses of the inefficient facets, by making it so that only the most efficient facets interface with the electrode.

“This means, at the macroscale, the material could possibly approach its theoretical energy conversion limit of 31%,” said Ian Sharp, another of the corresponding authors.

Wanted man captured thanks to facial recognition

A Chinese man who was wanted by police for “economic crimes” – which can include anything from tax evasion to the theft of public property – was arrested at a music concert in China after facial recognition technology spotted him inside the venue.

Source: Abacus News

SpaceX president commits to city-to-city rocket travel

SpaceX president and chief operating officer Gwynne Shotwell has reiterated the company’s plans to make city-to-city travel — on Earth — using a rocket that’s designed for outer space a reality. Shotwell says the tech will be operational “within a decade, for sure.”

Source: Recode

Businessman wins battle with Google over 'right to be forgotten'

A businessman fighting for the "right to be forgotten" has won a UK High Court action against Google.. The businessman served six months’ in prison for “conspiracy to carry out surveillance”, and the judge agreed to an “appropriate delisting order".

Source: Press Gazette

UK launched cyber attack on Islamic State

The UK has conducted a "major offensive cyber campaign" against the Islamic State group, the director of the intelligence agency GCHQ, Jeremy Fleming, has revealed. The operation hindered the group's ability to co-ordinate attacks and suppressed its propaganda.

Source: BBC

Goldman Sachs consider whether curing patients is bad for business

Goldman Sachs analysts have attempted to tackle the question of whether pioneering "gene therapy" treatment will be bad for business in the long run. "Is curing patients a sustainable business model?" analysts ask in a report entitled "The Genome Revolution."

Source: CNBC

Four-armed robot performing surgery in the UK

A £1.5m "robotic" surgeon, controlled using a computer console, is being used to shorten the time patients spend recovering after operations. The da Vinci Xi machine is the only one in the country being used for upper gastrointestinal surgery.

Source: BBC

Virgin Galactic rocket planes go past the speed of sound

Virgin Galactic completed its first powered flight in nearly four years when Richard Branson's space company launched its Unity spacecraft, which reached supersonic speeds before safely landing. “We’ve been working towards this moment for a long time,” Virgin Galactic CEO George Whitesides said in an email to Quartz.

Source: Quartz

Google employees protest being in "the business of war"

Thousands of Google employees, including dozens of senior engineers, have signed a letter protesting the company’s involvement in a Pentagon program that uses AI to interpret video imagery and could be used to improve the targeting of drone strikes. The letter, which is circulating inside Google, has garnered more than 3,100 signatures

Source: New York Times

Computer system transcribes words users “speak silently”

MIT researchers have developed a computer interface that transcribes words that the user verbalises internally but does not actually speak aloud. The wearable device picks up neuromuscular signals in the jaw and face that are triggered by internal verbalisations — saying words “in your head” — but are undetectable to the human eye.

Source: MIT News

Drones could be used to penalise bad farming

A report by a coalition of environmental campaigners is arguing squadrons of drones should be deployed to locate and penalise farmers who let soil run off their fields. Their report says drones can help to spot bad farming, which is said to cost more than £1.2bn a year by clogging rivers and contributing to floods.

Source: BBC

Californian company unveil space hotel

Orion Span, a California company, has unveiled its Aurora Station, a commercial space station that would house a luxury hotel. The idea is to put the craft in low-earth orbit, about 200 miles up, with a stay at the hotel likely to cost $9.5 million for a 12-day trip, but you can reserve a spot now with an $80,000 deposit.

UK mobile operators pay close to £1.4bn for 5G

An auction of frequencies for the next generation of mobile phone networks has raised £1.36bn, says regulator Ofcom. Vodafone, EE, O2 and Three all won the bandwidth needed for the future 5G mobile internet services, which are not expected to be launched until 2020.

Source: BBC