Efficiency - Page 58

Toshiba recently announced the fabrication of a film-based perovskite solar cell mini module with an impressive conversion efficiency of 10.5%. This efficiency rate was achieved in a 5 cm x 5 cm module and is stated by the company to be the highest yet recorded in a multi-cell mini module.

Toshiba achieved this by developing a fabrication process technology for film-based perovskite solar cells. The technology uses a film substrate and scribe process technology based on organic thin film solar cell module fabrication. Since this technology uses a flexible film substrate, it allows roll-to-roll fabrication that reduces costs. Toshiba will continue to refine the technology and expects to see further improvements in efficiency.

Researchers at the Universities of Cambridge and Milan (Politecnico di Milano) investigated the speed at which electrons (created as sunlight hits perovskite solar cell) need to reach the cell's electrode to be converted into flowing electric current before their energy starts to decline. The scientists found that perovskite solar cells will need to take advantage of femtosecond events (about a millionth of a billionth of a second) to stretch the limits of their energy conversion efficiency.

If the cells manage to work that fast, they could achieve an efficiency of 30% or maybe even more, which is currently thought to be the greatest efficiency that solar cells could achieve. Today's best silicon-based solar cells typically operate at efficiencies closer to 20%, but perovskite cells are thinner and regarded as having potential to surpass silicon cells' efficiency.

Researchers from KAUST have found that perovskite thin films for use in solar cells are more effective when glycol ethers are added to the film-forming mix. "It yields more uniform thin films with improved structure and efficiency", explains the team.

"Our aim was to improve the quality of perovskite thin films," say the researchers. The team decided to add glycol ethers to the manufacturing process because they knew these chemicals had previously been used to help create layers of metal oxides. By trying different glycol ether mixtures and conditions the researchers eventually gained better control over the formation of their perovskite thin films, by significantly improving the structure and alignment of the perovskite grains. This increased the reproducibility and efficiency of the perovskites so that they performed more efficiently in solar cell applications. The procedure also operates at lower temperatures than alternatives, which is an important factor in improving cost effectiveness.

Researchers at Shanghai Jiao Tong University in China and the Swiss Federal Institute of Technology have reported the development of a new technique to deposit high-quality large-area perovskite films that does not require solvents or vacuum processing. The method reportedly produces homogeneous films with relatively few defects, which leads to an efficiency of 12.1% for a solar module made from a methylammonium lead halide film that is just over 36 cm2 in size.

The research team has developed a new technique to produce large-area methylammonium lead halide (CH3NH3PbI3) perovskite films that relies on rapidly converting amine complex precursors (CH3NH3I·mCH3NH2 (where m is close to 3) and PbI2·nCH3NH2 (where n is close to 1) to perovskite films and then applying pressure to them.

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.

A team of Chinese and US scientists from Shenzhen Institute of Technology, Shijiazhuang Tiedao University, Peking University, Argonne National Laboratory, Institute of Metal Research, and University of Washington, have grown a monocrystalline version of a perovskite solar cell.

The created cell is reportedly of high quality and firmly incorporated on FTO/TiO2. To create it, the team has taken advantage of capillary effect and temperature gradient during the growth process. This achievement is considered to be critical, since FTO/TiO2 is regarded as the most extensively used electron-collecting substrate for perovskite solar cells, making the succeeding device fabrication straightforward. Although it won't replace monocrystalline silicon cells anytime soon (the new cell's efficiency is only 9%), it's the first time perovskite has been grown as a single cell.

Researchers from The University of Manchester have reported a new method that makes use of polystyrene particles (rather than expensive polymers) to reduce the costs and improve the stability of next-gen perovskite-based solar cells.

PSCs that use organometallic halide perovskite (OHP) as a light absorber face a known challenge of material degradation when exposed to water. This makes practical use quite limited. The cells also rely on a hole-transportation layer, which promotes the efficient movement of electrical current after exposure to sunlight. But manufacturing the hole-transportation organic materials is very costly and these lack long-term stability. This is where the use of insulating polystyrene microgel particles comes in.

Belgian research centre Imec has announced that it has boosted the performance of its its 4 cm2 perovskite/silicon tandem photovoltaic module to a power conversion efficiency of 23.9%. According to Imec, this is the first time that a module-on-cell stack structure has outperformed a standalone silicon solar cell.

'Two innovations are key to this achievement,' said group leader for thin-film photovoltaics at imec and perovskite PV program manager at Solliance. 'First, a different perovskite material (CsFAPbIBr) was used, largely improving the stability and conversion efficiency of the 4 cm 2 semi-transparent perovskite module to 15.3%. Second, the architecture of the stack was optimized for minimal optical losses by adding an anti-reflection texture on top of the module and a refractive index matching liquid between the perovskite module and the Si solar cell.'

Researchers at the Department of Energy's SLAC National Accelerator Laboratory have used a powerful "electron camera" to establish that light whirls atoms around in perovskites, potentially explaining the high efficiency of perovskite-based solar cell materials and providing clues for making better ones.

The scientists recorded movies that show that certain atoms in a perovskite respond to light within trillionths of a second in a very unusual manner. They explain that this may facilitate the transport of electric charges through the material and boost its efficiency.

Researchers affiliated with UNIST, the Korea Institute of Chemical Technology (KRICT) and Hanyang University have designed a cost-efficient method to produce inorganic-organic hybrid perovskite solar cells (PSCs), with outstanding efficiency performance of 22.1% in small cells and 19.7% in 1-square-centimeter cells.

A key feature of this technology is its ability to tackle the dominating defect in perovskite-halides, which is known to decrease the photoelectric efficiency. The team's results demonstrate that careful control of the growth conditions of perovskite layers with management of deficient halide anions is essential for realizing high-efficiency thin-film PSCs based on lead-halide-perovskite absorbers.