Efficiency - Page 59

The Air Force Research Laboratory (AFRL) in Ohio, USA, recently used perovskites to explore 3D printed solar cells. Using Optomec's aerosol jet technology, the team aims to develop a more efficient and low-cost production process for harnessing solar power.

The Air Force Research Laboratory is attempting to develop a manufacturing method which automates production of the solar cells to provide a viable industrial output. To do so, the team atomized perovskite materials which can be 3D printed with the Aerosol Jet technology machine. Having coated a flat surface with the droplets, the team created a solar cell with 15.4% efficiency.

Chinese perovskite materials startup Hangzhou Microquanta Semiconductor has reported that a 16-cm2 perovskite mini-module, certified by testing firm Newport in Montana, US has achieved a 16% conversion efficiency.

According to Microquanta, the perovskite mini-module 16% efficiency was achieved only three months after setting a prior record of 15.2%. Progress was made, primarily due to the focus on improving the deposition uniformity for large area thin films.

Researchers at the Georgia Institute of Technology have demonstrated that a low-temperature solution printing technique allows fabrication of high-efficiency perovskite-based solar cells with large crystals for minimizing grain boundaries. The meniscus-assisted solution printing (MASP) technique reportedly boosts power conversion efficiencies to nearly 20% by controlling crystal size and orientation.

The MASP process uses parallel plates (approximately 300 microns apart) to create a meniscus of ink containing the metal halide perovskite precursors. The bottom plate moves continuously, allowing solvent to evaporate at the meniscus edge to form crystalline perovskite. As the crystals form, fresh ink is drawn into the meniscus using the same physical process that forms a coffee ring on an absorbent surface such as paper. It was stated that the process could be scaled up to rapidly generate large areas of dense crystalline film on a variety of substrates, including flexible polymers.

Researchers at Aalto University have developed a method for improving perovskite-based solar cells, that builds on previous breakthroughs improving the efficiency and longevity of such cells using printing methods (carbon back contact based perovskite solar cells or CPSCs). These findings make it possible to further enhance the efficiency of these types of solar cells.

In the new method, the perovskite solar cells were exposed to 40-degrees in a chamber where humidity was kept in the level of 70% (±5%). This kind of environment normally degrades the properties of perovskite solar cells. In this case, the treatment led to surprising growth of the perovskite crystals, which naturally absorb sunlight and generate electricity. 'The photovoltaic performance was significantly enhanced, and the overall efficiency increased almost 45%,' say the researchers.

A multidisciplinary team at Berkeley Lab, both from the Molecular Foundry and the Joint Center for Artificial Photosynthesis, found a possible way to dramatically boost the efficiency of methylammonium lead iodide perovskite solar cells. The team discovered a surprising characteristic of a perovskite solar cell that could be exploited for higher efficiencies, possibly up to 31%.

Using photoconductive atomic force microscopy with nanometer-scale resolution, the scientists mapped two properties on the active layer of the solar cell that relate to its photovoltaic efficiency. The maps revealed a bumpy surface composed of grains about 200 nanometers in length. Each grain has multi-angled facets. Unexpectedly, the scientists discovered a big difference in energy conversion efficiency between facets on individual grains. They found poorly performing facets adjacent to highly efficient facets, with some facets approaching the material's theoretical energy conversion limit. The scientists say these top-performing facets could hold the secret to highly efficient solar cells if the material can be synthesized so that only very efficient facets develop.

EPFL Researchers, in collaboration with Michael Grätzel and Solaronix, have designed a low-cost and ultra-stable perovskite solar cell that has been operating at 11.2% efficiency for over a year, without loss in performance. This may represent a step towards solving the stability problem that currently poses a major obstacle towards commercialization of perovskite-based solar cell technology.

The team engineered what is known as a 2D/3D hybrid perovskite solar cell. This combines the enhanced stability of 2D perovskites with 3D forms, which efficiently absorb light across the entire visible spectrum and transport electrical charges. In this way, the scientists were able to fabricate efficient and ultra-stable solar cells, which is a crucial step for upscaling to a commercial level. The 2D/3D perovskite yields efficiencies of 12.9% (carbon-based architecture), and 14.6% (standard mesoporous solar cells).

Researchers from the Korea Advanced Institute of Science and Technology (KAIST) and Sungkyunkwan University have developed a perovskite-based semi-transparent solar cell that is reportedly highly efficient and functions very effectively as a thermal mirror.

A major key to achieving semitransparent solar cells is to develop a transparent electrode for the cell's uppermost layer that is compatible with the photoactive material. The Korean team developed a 'top transparent electrode' (TTE) that works well with perovskite solar cells. The TTE is based on a multilayer stack consisting of a metal film sandwiched between a high refractive index layer and an interfacial buffer layer. This TTE, placed as a solar cell's top-most layer, can be prepared without damaging ingredients used in the development of perovskite solar cells. Unlike conventional transparent electrodes that only transmit visible light, the team's TTE both allows visible light to pass through and reflects infrared rays.

Researchers from Lund University in Sweden and Fudan University in China have designed a new structural organization using perovskites that could greatly benefit perovskite-based solar cells. Perovskites, in their regular form, are sensitive to moisture and dissolve in contact with water, and even normal humidity deteriorates the material. Now, the researchers claim to have overcome this problem.

"We have succeeded in producing thin sheets with a water-repelling surface, making the whole construction much more stable. In addition, we have succeeded in orienting the sheets so as to obtain acceptable solar cells, with an efficiency of ten percent," says professor of chemical physics at Lund University.

Scientists at the Australian National University (ANU), which only last month reported a new world record in the development of perovskite-based solar cells (26% efficiency in converting sunlight into energy), have now announced a new achievement in making perovskite solar cells. Interestingly, this was done by learning from the blue Morpho Didius butterfly how to direct different colors of light.

The ANU team developed structures similar to the butterfly's tiny cone-shaped nanostructures that scatter light. These allow them to finely control the direction of light in experiments, which the scientists say can be very useful in next-generation solar cells, such as tandem solar cells with a perovskite and a silicon layer. In such tandem cells, the perovskite layers are meant to absorb the blue, green and ultraviolet colors of sunlight and leave the red, orange and yellow light to the silicon layer.

Researchers at the Karlsruhe Institute of Technology (KIT) in Germany have detected strips of nanostructures with alternating directions of polarization in the perovskite layers, that might serve as transport paths for charge carriers.

The perovskites used by the KIT team were defined as metal organic compounds with a special crystal structure and excellent photovoltaic properties. An interdisciplinary team of researchers analyzed perovskite solar cells by means of piezoresponse force microscopy and found ferroelectric nanostructures in the light-absorbing layers. Ferroelectric crystals form domains of identical electrical polarization direction. The KIT scientists observed that, during thin-layer development, lead iodide perovskites form about 100 nm wide stripes of ferroelectric domains with alternating electric fields. This alternating electric polarization in the material might play an important role in the transport of photogenerated charges out of the solar cell and, hence, explain the special photovoltaic properties of perovskites.