Efficiency - Page 52

The performance pf perovskite-based solar cells is affected by several factors, one of which can be ion defects that can move around. As these defects move, they affect the internal electric environment within the cell. The Perovskite material is responsible for absorbing light to create electronic charge, and also for helping to extract the charge into an external circuit before it is lost to a process called 'recombination'. Most of the detrimental recombination can occur in different locations within the solar cell. In some designs it occurs mainly within the perovskite, while in others it happens at the edges of the perovskite where it contacts the adjacent materials known as transport layers.

Now, researchers from the Universities of Portsmouth, Southampton and Bath have developed a way to adjust the properties of the transport layers to encourage the ionic defects within the perovskite to move in such a way that they suppress recombination and lead to more efficient charge extraction - increasing the proportion of the light energy falling on the surface of the cell that can ultimately be used.

Researchers from the Chinese Academy of Sciences have reported that the introduction of a certain amount of graphdiyne (25%), a form of carbon material invented by Chinese scientists with independent intellectual property rights, as a host material in perovskite solar cells can successfully push the device efficiency up to 21.01%, achieving multiple positive effects of highly crystalline qualities, large domain sizes and few grain boundaries.

The researchers also revealed that the current-voltage hysteresis was negligible, and device stability was improved as well. It was found that graphdiyne as the host active material significantly affects the crystallization, film morphology and a series of optoelectronic properties of perovskite active layer.

Oxford PV, a leading developer of perovskite solar cells, has announced a new, certified, 28% efficiency world record for its perovskite-based solar cell.

Oxford PV's 1 cm² perovskite-silicon tandem solar cell has achieved a 28% conversion efficiency, certified by the National Renewable Energy Laboratory. The achievement trumps Oxford PV's previous certified record of 27.3% efficiency for its perovskite-silicon solar cell, announced earlier this year.

Researchers from the Australian National University (ANU), in collaboration with researchers from and the California Institute of Technology, have developed a way to combine silicon with perovskites to achieve higher efficiencies and lower production costs. They believe that this could lead to cheaper and more efficient solar technology.

The new way to create crystalline silicon and perovskite tandem PV cells is claimed by the team to be the simplest method of doing so.

Researchers from Arizona State University have achieved 25.4% efficiency in their tandem solar cell stacked with perovskite and silicon. This follows, and surpasses, last year's achievement of 23.6% efficiency.

The team's improvement upon the record by nearly two percentage points was reached in a joint project with researchers at the University of Nebraska'Lincoln, predicting they'll be nearing 30% tandem efficiency within two years.

A team of researchers from Kaunas University of Technology (KTU), Lithuania, along with ones from Helmholtz Zentrum Berlin (HZB) science institute, Germany, have designed a novel approach to the selective layer formation in perovskite solar cells. The molecule, synthesized by the KTU chemists, assembles itself into a monolayer, which can cover a variety of surfaces and function as a hole transporting material in a perovskite solar cell. This results in a reduction of the amount of materials used in the process, thus reducing costs.

The molecule in this work assembles itself into a monolayer and can evenly cover any oxide surface (including textured surfaces of the silicon solar cells used in tandem architectures. "It's not polymer, but smaller molecules, and the monolayer formed from them is very thin. This, and the fact that the monolayer is being formed through dipping the surface into the solution makes this method much cheaper than the existing alternatives. Also, the synthesis of our compound is a much shorter process than that of the polymer usually used in production of perovskite solar cells", says Ernestas Kasparavičius, PhD student at KTU Faculty of Chemical Technology.

Researchers at the University of California, Los Angeles have used a polymer film to reduce defects in the light-absorbing perovskite, producing solar cells that are efficient and relatively robust.

The team explains that perovskites usually used in solar cells typically contain an organic cation and lead halide anions. But the heat treatment used to convert the perovskite's precursors into a crystalline layer can also drive out some of these organic cations. This leaves defects in the material's structure that hamper its performance and potentially make it less stable to moisture, heat, and even sunlight itself.

An international team of researchers led by the U.S. Department of Energy's SLAC National Accelerator Laboratory (that also included, among others, researchers from NIST, the University of Bath, Kings College London and Yonsei University) has gained new understanding of the movement of atoms in perovskite materials and how it affects the functioning of those materials. The results could explain why perovskite solar cells are so efficient and aid the quest to design hot-carrier solar cells, a theorized technology that would almost double the efficiency limits of conventional solar cells by converting more sunlight into usable electrical energy.

Common materials that make up conventional solar cells display a nearly rigid arrangement of atoms with little movement. In hybrid perovskites, however, the arrangements are more flexible and atoms move around more freely, an effect that impacts the performance of the solar cells but has been difficult to measure.

Researchers at the University of Cambridge have announced a new efficiency record for LEDs based on perovskite semiconductors, reportedly rivaling that of the best organic LEDs (OLEDs).

The team stated that compared to OLEDs, which are widely used in high-end consumer electronics, the perovskite-based LEDs can be made at much lower costs, and can be tuned to emit light across the visible and near-infrared spectra with high color purity.

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.