December 2016

2016 is soon over - and it was another exciting year for the perovskite industry. Researchers continue to innovate and develop more efficient solar panels, and it seems that commercialization of perovskite solar panels is approaching.

Here are the top 10 stories posted on Perovskite-Info in 2016, ranked by popularity (i.e. how many people read the story):

1. Breakthrough reproducibility achieved for perovskite solar cells (Mar 21)
2. Perovskite-silicon tandem solar cells reach 25.5% efficiency (Apr 13)
3. Semi-transparent perovskite PV modules created by imec (Jun 1)
4. EPFL team creates low-cost hole-transport material that improves efficiency of perovskite solar cells (Jan 20)
5. A new electron transport layer increase power conversion efficiency in perovskite solar cells (Jan 5)
6. Flexible perovskite-perovskite solar cells reach 21.7% efficiency (Nov 9)
7. Dyesol gets ready to launch a Major Area Demonstration Prototype for its perovskite PV technology (Feb 8)
8. Spray-on perovskite solar cells close to commercialization (Aug 7)
9. Water-resistant perovskite solar cell maintains efficiency (Jan 25)
10. Graphene-perovskite solar cells exceed 18% efficiency (Oct 5)

Scientists at Imperial College London have conducted experiments to follow the direction in which electrons move in perovskite solar cells when they are generated with a short pulse of light. They found that the mobile charged defects are still present even in solar cells with very efficient contact materials, despite these cells showing no hysteresis. Hysteresis was only found when cells suffered the combined effects of both the defects and poor selectivity at the contacts.

perovskite films contain charged defects that tend to impair their performance. Slow movement of these defects is thought to be responsible for a process known as hysteresis, which leads to irregularities in the efficiency with which light is converted to electrical current. Light-generated electricity exits the solar cell in the form of electrons to be harnessed. This is done via 'contacts' that sandwich the light-absorbing film. Previously, scientists have managed to address hysteresis by using more 'selective' contact materials that ensure a one-way flow of electrons out of the solar cell.

Researchers at OIST (Okinawa Institute of Science and Technology) have been investigating the cause of rapid degradation of perovskite solar cells. Their conclusions suggested that the degradation of MAPbI3 perovskites may not be a fixable issue, since iodide-based perovskites produce a gaseous form of iodine, I2, during operation, which in turn causes further degradation of perovskite.

In contrary to many researchers that have pointed to external sources (like moisture, atmospheric oxygen and heat) as the cause of MAPbI3 degradation, the fact that these solar cells continue to degrade even in the absence of these factors led the OIST team to believe that a property intrinsic to these cells was causing the breakdown of material.

Researchers from the National Institute for Materials Science in Japan have developed new additives for the hole-transporting layer of perovskite solar cells, which aim to greatly improve cell stability. When placed in the dark, the cells did not show signs of deterioration even after 1,000 hours of testing, and under continuous light soaking, they lasted six times longer (in terms of the time it takes for their power conversion efficiencies to fall to 85% of their initial states) compared to cells treated with conventional additives.

The researchers hope that these results will accelerate the commercialization of perovskite solar cells. The research group directed its focus on a pyridine-based additive, TBP, which is used as an additive in a hole-transporting layer in the mesoporous-type cell structure. After conducting experiments and analyzing the results, the group found that chemical reactions occurring between TBP and perovskite materials were one of the major causes of stability deterioration.

Researchers at the EPFL, along with scientists from Luxembourg Institute of Science and Technology (LIST) have used microscopy with mass spectrometry to study the nanoscale elemental distribution of mixed perovskites, which is particularly relevant for photovoltaic reproducibility and efficiency.

Perovskite are usually deposited as thin films on a surface, and they self-organize into crystals capable of being used for efficient solar cells. Limited information is available about the self-organization of the material, or how the different elements distribute - all of which is vital for optimizing perovskite photovoltaics. This is why the team tried to reveal significant micro- and nanoscale elemental and structural properties in self-organizing mixed perovskite films.

Researchers at Eindhoven University of Technology (TU/e) and research institute ECN (part of the Solliance collective) have found that adding a thin layer of aluminum oxide helps protect a perovskite solar cell against humidity, as well as add a yield boost of 3%.

The scientists covered the sensitive layer of perovskite with a few atomic layers of aluminum oxide to protect against degradation caused by humidity. These layers are contained within the solar cell, between the layers of perovskite and electric contact. The researchers chose aluminum oxide (Al2O3) since it can form immediately on any kind of surface. The team explained that despite the fact that Al2O3 has electrically insulating properties, it can still be used as a buffer layer between the semi-conductive perovskite and the conductive contacts by limiting the thickness of the layer to one nanometer or less. This way, charge carriers can then tunnel electrically through the insulator layer.

Oxford Photovoltaics recently announced an equity investment of £8.1 million (around US $10.2 million), adding to the £8.7 million first close investment announced in October 2016. The bulk of this investment will reportedly come from three new strategic investors: Statoil ASA, Legal & General Capital and a technology-focused, innovative family fund investor.

Oxford PV recently announced the acquisition of a pilot line site in Germany and, in the beginning of December 2016, announced a Joint Development Agreement with a major solar panel manufacturer to scale the technology towards commercialization. This additional injection of funds will hopefully help accelerate these development activities as well as support the next generation product research in the UK.

Oxford PV has announced a joint development agreement with an unnamed global solar cell and module manufacturer, as an additional step in the company's quest for commercialization of its perovskite solar technology.

The two companies will will work together to move Oxford PV's technology from lab scale to manufacturing-ready status, with most of the work taking place at the pilot line site in Germany that Oxford PV acquired recently.

Researchers at Australia's University of New South Wales announced the achievement of the highest efficiency rating with the largest perovskite solar cells to date. The 12.1% efficiency rating was for a 16 cm2 perovskite solar cell, the largest single perovskite photovoltaic cell certified with the highest energy conversion efficiency, and was independently confirmed by the international testing centre Newport Corp, in Bozeman, Montana. The new cell is at least 10 times bigger than the current certified high-efficiency perovskite solar cells on record.

The researchers also achieved an 18% efficiency rating on a 1.2 cm2 single perovskite cell, and an 11.5% for a 16 cm2 four-cell perovskite mini-module, both independently certified by Newport. The team estimated that it will be be able to "get to 24% within a year or so".