October 2018

Some of the key challenges for hybrid organic-inorganic perovskite solar cells are their limited stability, scalability, and molecular level engineering. Researchers at the Laboratory of Photonics and Interfaces (LPI) and Laboratory of Magnetic Resonance (LMR) at EPFL show how molecular engineering of multifunctional molecular modulators (MMMs) and using solid-state nuclear magnetic resonance (NMR) to investigate their role in double-cation pure-iodide perovskites can lead to stable, scalable, and efficient perovskite solar cells.

The objective of the team lead by Professor Grätzel (LPI), in collaboration with the group of Professor Lyndon Emsley (LMR) was to tackle the above-mentioned challenges through rational molecular design in conjunction with solid-state NMR, as a unique technique for probing interactions within the perovskite material at the atomic level. The team designed a series of organic molecules equipped with specific functions that act as molecular modulators (MMs), which interact with the perovskite surface through noncovalent interactions, such as hydrogen bonding or metal coordination. While hydrogen bonding can affect the electronic quality of the material, coordination to the metal cation sites could ensure suppression of some of the structural defects, such as under-coordinated metal ions.

Researchers at Helmholtz-Zentrum Berlin (HZB) have demonstrated 25.5% efficiency for monolithic perovskite/silicon tandem solar cells using textured foil. In addition, the impact of texture position on performance and energy yield is simulated in their new work.

Tandem solar cell device schematics of the experimentally realized architecture and SEM cross section image of the top cell

The research team used a textured light management (LM) foil on the front-side of a tandem solar cell processed on a wafer with planar front-side and textured back-side. Consequently, the PCE of monolithic, 2-terminal perovskite/silicon-heterojunction tandem solar cells was improved from 23.4% to 25.5%. This approach replaced the use of textured silicon wafers, that can be utilized for light management but are typically not compatible with perovskite solution processing.

Researchers from the National University of Singapore (NUS) have developed novel lead halide perovskite nanocrystals that are highly sensitive to X-ray irradiation. By incorporating these nanocrystals into flat-panel X-ray imagers, the team developed a new type of detector that could sense X-rays at a radiation dose about 400 times lower than the standard dose used in current medical diagnostics. These nanocrystals are also cheaper than the inorganic crystals used in conventional X-ray imaging machines.

"Our technology uses a much lower radiation dose to deliver higher resolution images, and it can also be used for rapid, real-time X-ray imaging. It shows great promise in revolutionizing imaging technology for the medical and electronics industries. For patients, this means lower cost of X-ray imaging and less radiation risk," said the research team.

The Solar Energy Technologies Office Fiscal Year 2018 (SETO FY2018) funding program addresses the affordability, flexibility, and performance of solar technologies. This program funds early-stage research projects that advance both solar photovoltaic (PV) and concentrating solar-thermal power (CSP) technologies.

Earlier this month, the U.S. Department of Energy announced it would provide $53 million in funding for 53 projects in the SETO FY2018 funding program. Of those projects, 31 will focus on photovoltaics research and development. Within this topic, the office has also selected projects that will develop and test new ways to accelerate the integration of emerging technologies into the solar industry.

Researchers at Kaunas University of Technology (KTU), Lithuania, along with ones from Vilnius University and the Swiss Federal Institute of Technology, Lausanne (EPFL), have uncovered one of the possible reasons behind the short lifespan of perovskite solar cells and have offered solutions. The scientists have found that hole transporting materials used in perovskite solar cells are reacting with one of the most popular additives, tert-butylpyridine, which has a negative impact on overall device performance.

Professor Vytautas Getautis from the KTU Faculty of Chemical Technology says that so far, no attention has been paid to the possible interaction between the elements of the solar cell. For the first time, KTU chemists have uncovered the chemical reaction between the components of the hole transporting layer composition ' the semiconductor and the additive used to improve the performance of the solar cell.

Two papers have recently been published, reporting on perovskite-based LEDs. The efficiencies with which some perovskite LEDs (PLEDs) produce light from electrons already seem to rival those of OLEDs.

Both papers, by Cao et al. and Lin et al., have developed PLEDs that break an important technological barrier: the external quantum efficiency (EQE) of the devices, which quantifies the number of photons produced per electron consumed, is greater than 20%. There are several similarities between the devices reported by the two groups. Perhaps most notably, the active (emissive) perovskite layer is about 200 nanometres thick in both cases, and is sandwiched between two relatively simple electrodes. This design is called a planar structure, and is the most basic manifestation of diodes made from thin films of materials. The electrodes are appropriately modified to ensure that electrons and holes (quasiparticles formed by the absence of electrons in atomic lattices) are efficiently pumped into the perovskite. As in all LEDs, when electrons meet holes, they can release energy in the form of photons through a process known as radiative recombination.

Korver Corp., an emerging solar and renewable energy company, has provided an update regarding the Company's new strategic direction in the solar energy sector. Korver has now decided to focus on its mission to develop high-efficiency commercially-manufactured Perovskite Silicon Tandem (PST) solar cells.

Mark Brown, President and CEO of Korver Corp., stated, "Our prior research has resulted in the development of highly efficient Perovskite Silicon Tandem solar cells. We plan to reach an efficiency mark of over 30% on a commercial scale by combining perovskite solar with the best silicon technologies on the market today and our own proprietary innovations. Currently, we are working towards scalability and commercial manufacturing of our PST solar cells that could change the way the world produces and consumes energy on a grand scale. We are excited to take the first mover advantage with the next big thing in solar energy."

Researchers at Pacific Northwest National Laboratory are evaluating perovskite-structured rare-earth nickelates as alternatives to replace two reactions that are considered a challenge when it comes to electrocatalysts: the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Both are important for the development of better fuel cells, metal-air batteries, and electrolytic water-splitting.

Materials such as platinum, iridium oxide and ruthenium oxide are well suited for these reactions, but they are scarce and expensive. The team has been working to study perovskite-structured rare-earth nickelates (RNiO₃) that can serve as bifunctional catalysts capable of performing both OER and ORR.

Researchers at Linköping University and Shenzhen University have shown how inorganic perovskites can be used to produce low-cost and efficient photodetectors that transfer both text and music. "It's a promising material for future rapid optical communication," says Feng Gao, researcher at Linköping University.

"Perovskites of inorganic materials have a huge potential to influence the development of optical communication. These materials have rapid response times, are simple to manufacture, and are extremely stable." says Feng Gao.

A next-generation optical material based on perovskite nanoparticles can achieve vivid colors even on very large screens. Due to their high color purity and low cost advantages, it has also gained much interests in industry. A recent study including researchers with UNIST has introduced a simple technique to extract the three primary colors (red, blue, green) from this material.

This innovative work was led by Professor Jin Young Kim in the School of Energy and Chemical Engineering at UNIST. In the study, the research team introduced a simple technique that freely controls light emitting spectra by adjusting the anion halides in perovskite materials. The key is to adjust the anion halides by dissolving them in solvents to achieve red, blue and green lights. Application of this technique to LEDs can result in crystal-clear picture quality.