Efficiency - Page 65

A team of scientists from the School of Science and Engineering in Shanghai have developed a multi-functional inverse opal-like TiO2 electron transport layer (IOT-ETL) for a cost-efficient perovskite solar cell with high power conversion Efficiency.

The researchers introduced an IOT-ETL, produced by a simple polystyrene-assistant method. It was created to replace the traditional compact layer and mesoporous scaffold layer in perovskite solar cells. The new devise improved the light harvesting efficiency by enhancing the light scatting property in the devices.

Researchers at the Japanese Kyoto University have designed a material called HND-Azulene, that can, when used as a hole-transporting material (HTM), increase the efficiency of perovskite solar cells by up to 20% when compared to the commonly used Spiro-OMeTAD. Such perovskite PV cells have exhibited a power conversion efficiency of over 16.5%, compared to an efficiency of 13.6% for cells using the current standard Spiro-OMeTAD.

The research team has designed and synthesized the HND-Azulene system with a sheet-shaped structure. Based on the evaluation and a comparison of the optoelectronic and electrochemical properties of HND-Azulene and Spiro-OMeTAD, the researchers were been able to determine the factors that are required for HTMs to act efficiently in perovskite solar cells. In line with these new molecular design principles, they believe that more sophisticated HTMs should be easily attainable.

Dyesol, the Australia-based renewable energy supplier and leader in Perovskite Solar Cell technology, announced that a research team at the Ecole Polytechnique Fédérale de Lausanne (EPFL) has established a remarkable efficiency for its Perovskite Solar Cells (PSC), with a conversion efficiency of 21.02%.

This conversion efficiency was certified at the laboratories of Newport Corporation in Bozeman, Montana USA. This new conversion efficiency eclipses the previous record of 20.1%.

Researchers at the Swiss materials science and technology research institute, Empa, have discovered a new way to produce thin film tandem solar cells using perovskite crystals. This discovery is a major milestone on the path to produce high-efficiency solar cells with low cost procedures.

In tandem solar cells, energy is harvested in two stages, which results in the conversion of sunlight into electricity becoming much more efficient. The top cell is semi-transparent and allows efficient conversion of large energy photons into electricity and the bottom cell converts the remaining transmitted low energy photons in an optimum manner. The tandem solar cells provide 20.5% efficiency when converting light to electricity and the researchers said that this can be increased to 30%. Empa researchers have further emphasized that it has a lot of potential to provide better conversion of solar spectrum into electricity.

Researchers from Helmholtz-Zentrum Berlin (HZB) and the university École polytechnique fédérale de Lausanne(EPFL) in Switzerland have combined a silicon heterojunction solar cell with a perovskite solar cell monolithically into a tandem device and reached a record efficiency of 18%, stating it has the potential to reach 30% after additional modifications.

Designing such silicon-perovskite tandem cells can be challenging, as perovskite cells tend to require coating onto titanium dioxide layers, which must first be sintered at around 500 °C. The amorphous silicon layers that cover the crystalline silicon wafer in silicon heterojunction degrade at this temperature. Now the team from EPFL and HZB has managed to overcome hurdles and manufacture this kind of monolithic tandem cell, by depositing a layer of tin dioxide at low temperatures instead of using titanium dioxide. A thin layer of perovskite could then be spin-coated onto this intermediate layer and covered with hole-conductor material. The team also used a transparent protective layer to avoid the metal oxides sputtering and consequently destroying the perovskite layer and hole-conductor material.

A research team from Japan's National Institute for Materials Science (NIMS) has developed a new method of fabricating high-quality perovskite materials, capable of utilizing longer-wavelength sunlight of 800 nm or longer. The method may mark a new approach to enhance the efficiency of perovskite solar cells.

Perovskite solar cells currently possess optical absorption spectra that lean toward shorter wavelengths. To improve the energy conversion efficiency of these cells, it is crucial to develop perovskite materials with optical absorption spectra expanded to include longer wavelengths. This is why several research institutes are developing perovskite materials that include two types of cations, MA and FA, capable of absorbing light in the longer wavelength region. However, these cations are not without issues - mainly that their mixing ratio and crystallization temperature are difficult to control. Moreover, due to their tendency to form a mixed crystal phase, there had been no effective method established to fabricate high-purity, single-crystalline perovskite materials.

Scientists at the National Institute for Materials Science (NIMS) announced the improvement of power conversion efficiency (PCE) of perovskite solar cells to over 16% while employing cells that were greater than 1 cm2. The high efficiency cells also passed the durability test (exposure to AM 1.5G 100 mW/cm2 sunlight for 1,000 hours), which is considered to be a basic criterion for practical use. These achievements were made by replacing the conventional organic materials with inorganic materials as the electron and hole extraction layers of the solar cells.

The researchers replaced the conventional organic materials with robust inorganic materials for use in electron and hole extraction layers. Since these layers have high electrical resistance, it was necessary to reduce the thickness of the layers to several nanometers. However, as the area of these thin layers increases, the occurrence of defects called pinholes also increases, leading to decreased PCEs. To deal with this problem, the researchers increased the electrical conductivity of these layers by more than 10 times through heavily doping both electron and hole extraction layers. In this way, they fabricated layers that have fewer pinholes over wide areas and are applicable at thicknesses of up to 10 to 20 nm. Using these layers, a PCE of 16% was repeatedly attained while employing cells that were greater than 1 cm2. The use of inorganic materials also contributed to PCE reduction within 10% even after undergoing 1,000 hours of continuous exposure to sunlight at an intensity of 1 sun, demonstrating outstanding reliability.

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.