October 2015

Scientists at Nanjing University of Science and Technology, China, and colleagues have used quantum dots based on perovskites for QD-based light-emitting devices (QLEDs). These (completely inorganic) materials reportedly solve the stability problem of previously developed hybrid organic'inorganic halide perovskites.

Quantum dots (QDs) are nanometer-sized semiconductor materials with highly tunable properties such as bandgap, emission color, and absorption spectrum. These characteristics depend on their size and shape, which can be controlled during the synthesis. The quantum dots' luminescence wavelength can be tuned by both their size and by the halide ratio. In this research, the team made blue, green, and yellow QLEDs with high quantum yields, using the perovskite quantum dots as the emitting layer. The researchers state that this development could allow the design of new optoelectronic devices, such as displays, photodetectors, solar cells, and lasers.

A project by Cambridge-based DZP Technologies, which also received the prestigious 1851 Industrial Fellowship, targets the development and commercialization of innovative perovskite solar cells. The project will be carried out in collaboration with the University of Surrey's Advanced Technology Institute, aiming to overcome some of the necessary technical hurdles to realize perovskite solar cells.

Researchers at Ludwig Maximilian Univ. of Munich, Germany (LMU) have succeeded in synthesizing perovskite nanocrystals in the form of ultrathin nanoplatelets whose emission characteristics can be tuned by altering their thickness. The resulting nanoplatelets are about 300 times thinner than the perovskite films conventionally used in the fabrication of solar cells.

Despite their large surface area, these platelets emitted an intense blue luminescence, and the properties exhibited by these minuscule particles were deemed inexplicable in the context of classical physics. The scientists state that they can be accounted for only by the laws of quantum physics, as confirmed by theoretical calculations carried out by the team.

Researchers at ETH Zurich have built a perovskite-based memristor just 5 nanometres thick. The component has three stable resistive states, and as a result, it can not only store the 0 or 1 of a standard bit, but can also be used for information encoded by three states ' the 0, 1 and 2 of a 'trit'. This component could, therefore, be useful for a new type of IT that is not based on binary logic, but on a logic that provides for information located 'between' the 0 and 1, with interesting implications for what is referred to as fuzzy logic, which seeks to incorporate a form of uncertainty into the processing of digital information.

Another potential application is neuromorphic computing, which aims to use electronic components to reproduce the way in which neurons in the brain process information. The scientists explain that the properties of a memristor at a given point in time depend on what has happened before, and this mimics the behavior of neurons, which only transmit information once a specific activation threshold has been reached.

Renewable Energy and Power, a specialist in energy-saving technologies of LED lighting and solar cells, announced that the company signed a consulting agreement with G-Wave of San Jose, CA, to negotiate for license to a major university's Perovskite solar cell technology.

Researchers at the University of California, Los Angeles (UCLA) and the California NanoSystems Institute have managed to improve the stability of perovskite solar cells by using metal oxide layers. This novel assembly helps increase the service life of this kind of solar cells by over 10 times, with just a minimal loss to its conversion efficiency.

While many reasons exist for the fast disintegration of normally layered perovskite solar cells, the scientists claim that the key reason is the commonly used top organic buffer layer, which does not offer any stability and cannot effectively protect the perovskite material from moisture found in air. The buffer layers are crucial to cell construction as electricity, which is produced by the cell, is extracted through them. In this work, the organic layers were replaced with metal oxide layers, which sandwiched the perovskite material, thus providing adequate moisture protection. The change was very obvious. The newly formed metal oxide cells were able to withstand open-air storage conditions for 60 days at room temperature, and could retain 90% of its original solar conversion effectiveness.

Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) have revealed the cause for the short lifetime of perovskite solar cells with silver electrodes, and propose a mechanism for preventing it and improving the lifetime of such cells.

Silver electrodes are a less-expensive replacement for common gold electrodes, and to keep the cost even lower, the team in this study wanted to use solution-processed method to fabricate the layers of the solar cell, instead of expensive vacuum-based techniques. The problem of using silver electrodes and the solution-based method is that silver gets corroded within days of the solar cell fabrication. The corrosion makes the electrode turn yellow, and reduces the efficiency of the cell. The researchers analyzed the composition of the corroded silver electrode and identified the formation of silver iodide as the reason for the electrode corrosion. They also found that exposure to air accelerates the corrosion, when compared to dry nitrogen gas exposure.

Researchers from Brown University and the National Renewable Energy Lab (NREL) managed to attain better than a 15% energy conversion efficiency from perovskite solar cells larger than one square centimeter area, by using a newly developed fabrication method.

Efficiency of over 20%, which rivals traditional silicon cells, has already been reported in perovskite cells, but such high efficiency ratings have been achieved using cells only a tenth of a square centimeter in size, too small to be used in a solar panel. This research, however, shows that it is feasible to obtain 15% efficiency on cells larger than a square centimeter through improved processing.

Researchers at the Helmholtz-Zentrum Berlin (HZB) developed a process for coating perovskite layers with graphene for the first time, so that the graphene acts as a front contact.

A traditional silicon absorber converts the red portion of the solar spectrum very effectively into electrical energy, whereas the blue portions are partially lost as heat. To reduce this loss, the silicon cell can be combined with an additional solar cell that primarily converts the blue portions and a particularly effective complement to conventional silicon is perovskite. However, it is normally very difficult to provide the perovskite layer with a transparent front contact. While sputter deposition of indium tin oxide (ITO) is common practice for inorganic silicon solar cells, this technique destroys the organic components of a perovskite cell.

Australia-based Dyesol has been awarded a $449,000 grant from the Australian Renewable Energy Agency (ARENA) to commercialize an innovative, very high efficiency perovskite solar cell.

ARENA has stated that the funding would enable Dyesol to create a roadmap setting out the steps needed to take its perovskite solar cell technology from the lab to a commercially available product. Dyesol will map out the techniques and requirements for working towards scalable manufacturing of high-quality, uniform perovskite cells that achieve efficiency, durability and stability targets.