Graphene as a front contact for silicon-perovskite tandem solar cells

World’s first 2D sheets of organic-inorganic hybrid perovskites grown from a solution

Researchers at the Department of Energy’s Lawrence Berkeley National Laboratory have succeeded in growing atomically thin 2D sheets of organic-inorganic hybrid perovskites from a solution. The sheets are claimed to be of high quality and large in area. The scientists state that this is the first example of 2D atomically thin nanostructures made from ionic materials and that the results of this study open up opportunities for fundamental research on the synthesis and characterization of atomically thin 2D hybrid perovskites and introduce a new family of 2D solution-processed semiconductors for nanoscale optoelectronic devices, such as field effect transistors and photodetectors. Perovskite materialsTechnical / researchAbove are World’s first 2D sheets of organic-inorganic hybrid perovskites grown from a solution web publication,Hope can help you.

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.

The HZB scientists have found an innovative solution to that problem, in a process that covers the perovskite layer evenly with graphene – forming an extremely thin film that is highly conductive and highly transparent. For that to happen, the researchers first promoted growth of the graphene onto copper foil from a methane atmosphere at about 1000 degrees Celsius. For the subsequent steps, they stabilise the fragile layer with a polymer that protects the graphene from cracking. In the following step, they etch away the copper foil. This enables the transfer of the protected graphene film onto the perovskite. This is normally carried out in water, where the graphene film floats on the surface and is “fished out” by the solar cell. However, in this case this technique does not work, because the performance of the perovskite degrades with moisture. Therefore it was necessary to find another liquid that does not attack perovskite.

Tests proved that the graphene layer acts as an ideal front contact in several respects. Thanks to its high transparency, none of the sunlight鈥檚 energy is lost in this layer. But the main advantage is that there are no open-circuit voltage losses, that are commonly observed for sputtered ITO layers. This increases the overall conversion efficiency. The solution is also comparatively simple and inexpensive to implement. The success in implementing graphene in a perovskite solar cell for the first time enabled the scientists to build a high-efficiency tandem device.

Helmholtz BerlinPerovskite applicationsPerovskite SolarHybrids and related materialsEfficiency
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Perovskite solar cells may recharge electric cars’ batteries

Scientists at Case Western Reserve University that have been experimenting with the use of small perovskite solar cells to help recharge the batteries of electric cars state that they have found a system that performs better than any other. They wired four perovskite solar cells in series to directly photo-charge lithium batteries with 7.8% efficiency. The researchers say that they have found the right match between the solar cell and battery. The coupling appears to have outperformed all other reported pairings of photo-charging components and compatible batteries or supercapacitors. They have created cells with three layers converted into a single perovskite film and then wired four of the 1 mm square cells in series, achieving a solar-to-electric power conversion efficiency of 12.65%. When hooked up to charge small coin-sized lithium-ion…