Hybrids and related materials - Page 7

Oxford Photovoltaics Germany, a subsidiary of Oxford PV, has received funding of €15 million form the European Investment Bank (EIB), to support the commercialization of its perovskite-on-silicon tandem solar cell technology.

The funding is the first in Germany under InnovFin - EU Finance for Innovators' Energy Demonstrator Projects. It relies on the financial backing of the European Union under Horizon 2010 Financial Instruments, aimed at supporting European innovators such as Oxford PV, tackling tomorrow's challenges and supporting climate action.

Researchers at the National Renewable Energy Laboratory (NREL) and the University of Washington have designed an interesting strategy for driving down the cost of solar cells while ramping up efficiency: the team developed a high cost, high efficiency quantum dot solar cell for space applications, and provided the expensive solar cell up with a cheaper perovskite layer. The combined solar cell would be aimed at terrestrial applications with a more moderate price point. Note that in the proposed lower cost solar cell, the cheap layer is not the only role for perovskite. The expensive quantum dot layer would also be made of perovskite.

The NREL team explains that colloidal quantum dots are electronic materials and because of their astonishingly small size (typically 3-20 nanometers in dimension) they possess fascinating optical properties. That first quantum dot solar cell had a conversion efficiency of just 2.9% and was based on a lead sulfide formula. Things moved along quickly after that, and NREL noted a record of 12% for lead sulfide achieved by the University of Toronto just last year.

Oxford Photovoltaics is to receive financing from the European Investment Bank (EIB) for its planned pilot site in Germany. The bank is considering providing EUR 15 million ($17.6 million USD) for the project, which will turn an existing PV thin-film module factory in Germany into a "first-of-its-kind" plant for the production of tandem silicon-perovskite PV cells.

According to EIB, the site will allow the company to demonstrate its perovskite technology at full wafer scale in pilot volumes and deploy perovskite on silicon tandem cells. The total cost of the project is EUR 30 million.

A team of researchers at the Netherlands' AMOLF institute has modelled the performance of tandem perovskite/silicon solar cells under real-world climate conditions, and found that the tandem cells are just a little more efficient than the Si cell alone in the cloudy climates of the test locations. The research shows, however, that if correctly optimized, this type of cell could perform at efficiency levels above 38%.

Discounting all parasitic absorption in the transparent contacts of the perovskite cell, say the researchers, the tandem cells exhibited efficiency advantages of between 1.8% and 3.3%, far less than expected under ideal conditions.

Researchers at Purdue University and the National Renewable Energy Laboratory have found that certain hybrid perovskites could double the amount of electricity produced without a significant cost increase. This could help in creating efficient solar cells thinner than conventional silicon solar cells, that are also flexible, cheap and easy to make.

The material, a crystalline structure that contains both inorganic materials (iodine and lead) and an organic material (methyl-ammonium), boosts the efficiency so that it can carry two-thirds of the energy from light without losing as much energy to heat.

A collaboration between researchers at Stanford University and Arizona State University (ASU) resulted in a new perovskite-silicon tandem solar cell that converts sunlight to electricity with 23.6% efficiency. The team stated that work is being put into reaching 30% efficiency, and they believe that they "could be there within two years".

In the tandem cell created by Stanford and ASU, the top cell is composed of a perovskite compound and the bottom cell is made of silicon that is specifically tuned to capture infrared light. The perovskite and silicon cells boast efficiency of 15 and 21%, respectively. ASU provided the silicon bottom cell, while Stanford researchers fabricated the perovskite compound and subsequent cells. Throughout the yearlong collaboration, the ASU team also provided modeling support to design the tandem for maximum current generation, while the Stanford team characterized the tandem cells.

Researchers at the Korean UNIST have announced that they have successfully developed a new way to increase energy efficiency of perovskite-based metal-air batteries by using a conducting polymer.

In the cathode of metal-air batteries or fuel cells, oxygen is reduced to metal oxide or water. Catalysts are required to accelerate the reaction. While platinum is an efficient choice, its high price remains a problem. In the study, the team reported that catalytic activity of a provskite material which can be used as a substitute to platinum was dramatically enhanced by simply adding a kind of conducting polymer, polypyrrole.

Researchers at Australia National University (ANU) have developed a novel manufacturing technique for perovskite solar cells, that may boost their efficiency. The ANU team sees this as a breakthrough that 'significantly improved' the performance of perovskite solar cells, which can combine with conventional silicon solar cells to produce more efficient solar electricity.

The ANU team designed an approach that requires a small amount of the element indium to be added to one of the cell's layers, which is claimed to result in a 25% increase in its power output. With perovskite better at converting visible light into electricity, and silicon more efficient in the infrared part of the spectrum, a combination of both is a promising path going forward.

Researchers from the University of California, Berkeley, and Lawrence Berkeley National Laboratory have developed a flexible perovskite solar cell that reaches an efficiency of 21.7%, a peak conversion efficiency of 26% and could be manufactured using a low cost roll-to-roll process.

Many previous attempts to merge two perovskite materials have failed because the materials degrade one another's electronic performance. This design was achieved using a new way of combining two perovskite solar cell materials ' each tuned to absorb a different wavelength or color of sunlight ' into one 'graded bandgap' solar cell that absorbs nearly the entire spectrum of visible light.

Researchers from the US National Renewable Energy Laboratory (NREL) have achieved 10.77% conversion efficiency with perovskite solar cells made from quantum dots with no organic components.

Solutions of all-inorganic perovskite quantum dots, showing intense photoluminescence when illuminated with UV light

The result was achieved with a thin film made of nanocrystals of cesium lead iodide (CsPbI3). The team discovered a method to keep the crystal structure in the all-inorganic perovskite material stable at room temperature, something that was previously possible only at temperatures exceeding 600 degrees Fahrenheit. The use of methyl acetate as an anti-solvent to remove excess unreacted precursors proved a crucial step in increasing the nanocrystals' stability.