Efficiency - Page 39

Researchers at UC Santa Barbara have discovered an important factor that limits the efficiency of perovskite solar cells.

Various possible defects in the lattice of hybrid perovskites had previously been considered as the potential cause of such limitations, but it was assumed that the organic molecules would remain intact. The team has now revealed that missing hydrogen atoms in these molecules can cause massive efficiency losses.

Researchers at the Karlsruhe Institute of Technology (KIT) have produced perovskite solar modules with greatly reduced loss of efficiency due to scaling. The team reported an efficiency of 18% for a perovskite solar module with an area of ''4cm² -a world record for vacuum-processed perovskite solar modules. To this end, they combined the series connection by laser with the vacuum processing of all layers of the solar cell.

"One of the main challenges is to transfer the efficiencies achieved on areas of a few square millimeters to typical solar module surfaces of a few hundred square centimeters," says Dr. Tobias Abzieher, who heads the development of perovskite solar cells deposited from a vacuum at the Light Technology Institute (LTI) of the KIT. Perovskite solar cells are often joined together to form large-area solar modules using the so-called monolithic series connection. For this purpose, structuring lines are introduced during the deposition of the individual layers of the solar cell, which causes the solar cell strips to be connected in series.

Solliance partners TNO, imec/EnergyVille and the Eindhoven University of Technology, have reported a 18.6% efficient highly near infrared transparent perovskite solar cell. When combined in a four terminal tandem configuration with an efficient Panasonic crystalline silicon (c-Si) cell or with a Miasolé flexible CIGS cell, the configuration delivered new record power conversion efficiencies of 28.7% and 27.0%, respectively.

The researchers explained that four terminal tandems allow to build on experience and practices already available in the industry. In addition, four terminal perovskite/c-Si tandems can be applied broadly and are, for example, very beneficial in combination with bifacial c-Si solar cells which, depending on the actual albedo, can readily achieve a total power generation density as high as 320 W/m².

Researchers from the Chinese Academy of Sciences (CAS) and Fuzhou University have reported a perovskite solar cell with an electron transport layer (ETL) based on Tin(IV) oxide (SnO₂) and crystalline polymeric carbon nitrides (cPCN).

The team explained that the modification of the SnO₂ layer with the cPCN is key to avoiding undesirable current-voltage hysteresis, which is responsible for reducing the cell's stability. This phenomenon tends to occur in electrical systems when current or voltage changes and the effects of the changes are delayed. It is dependent on the composition of the material, and ion migration and non-radiative recombination near interfaces are often considered responsible for the effect.

Researchers from Australia's Queensland University of Technology (QUT) and Swinburne University of Technology have reported the creation of resilient, high-efficiency triple-cation perovskite solar cells (PSCs) by incorporating carbon dots (CDs) derived from human hair into the perovskite film.

QUT's Professor Hongxia Wang's team had previously found that nanostructured carbon materials could be used to improve a cell's performance. In their recent work, they tried using the carbon nanodots on perovskite solar cells. After adding a solution of carbon dots into the process perovskites synthesis, Professor Wang's team found the carbon dots forming a wave-like layer where the perovskite crystals are surrounded by the carbon dots.

A team of researchers, led by South Korea's UNIST and KIER, and Switzerland's EPFL, has reached 25.6% power conversion efficiency of perovskite solar cells by introducing an anion engineering concept that uses pseudo-halide anion formate to suppress anion-vacancy defects and augment crystallinity.

Perovskite derivatives have been investigated to overcome instability issues with lead-based organic perovskite materials in ambient air and reduce the use of lead. Researchers have introduced various methods to improve conversion efficiency. An engineering concept using formate, which is the anion derived from formic acid, was introduced by researchers.

China-based Wuxi Utmost Light Technology (UtmoLight) has announced that it has reached a new world record of 20.5% power conversion efficiency for its perovskite mini-module with a designated area of 63.98 cm². The result was reportedly certified by the internationally recognized test center ' Japan Electrical Safety & Environment Technology Laboratories (JET).

UtmoLight plans to build production lines for manufacturing large-area perovskite solar modules to accelerate the commercialization of its perovskite photovoltaic technology.

A team of scientists, led by Professor Feng Yan from Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, and co-workers, recentky developed a novel method to overcome the drawback of grain boundaries (GBs) in perovskites without using defect passivation.

Several 2D materials, including black phosphorus (BP), MoS₂ and graphene oxide (GO), were specifically modified on the edge of perovskite GBs by a solution process. The 2D materials have high carrier mobilities, ultrathin thicknesses and smooth surfaces without dangling bonds. The PCEs of the devices are substantially enhanced by the 2D flakes, in which BP flakes can induce the highest relative enhancement of about 15%.

Researchers from Kanazawa University and Tokai University in Japan, in collaboration with other institutes, have developed a perovskite solar cell based on a titanium oxide (TiO₂) compact electron transport layer (ETL), which they claim is the most efficient PV device of its kind to be produced at the research level to date.

They researchers used a spray pyrolysis deposition (SPD) technique, which is generally used for temperature decomposition of organic material in the absence of oxygen. This process is known to provide excellent rate capability and high cycling stability. It is used in the chemical industry to produce ethylene, carbon and chemicals from petroleum, coal and even wood, in addition to producing coke from coal.

A research team, led by Los Alamos National Laboratory, has designed a simple solution for fabricating stable perovskite solar cells that is said to overcome the key bottleneck to large-scale production and commercialization of perovskite solar cells.

A new dipping process using a sulfolane additive creates high-performing perovskite solar cells. Image: LANL

The Los Alamos team, in collaboration with researchers from National Taiwan University (NTU), invented a one-step spin coating method by introducing sulfolane as an additive in the perovskite precursor, or the liquid material that creates the perovskite crystal through a chemical reaction. As in other fabrication methods, that crystal is then deposited on a substrate.