Efficiency - Page 29

Sekisui Chemical has announced that it will provide and install film-type perovskite solar cells to Umekita (Osaka) Station, to be developed by West Japan Railway Company.

The Company claims it has achieved outdoor durability of 10 years equivalent by means of original “sealing, film formation, materials and process technology,” creating a 30 cm-wide roll-to-roll manufacturing process. This manufacturing process has been successfully used to produce film-type perovskite solar cells with power generation efficiency of 15.0%. Currently, work is aiming to establish a manufacturing process for 1 m-wide rolls that offers more improvements in durability and power generation efficiency with a view to practical application and the New Energy and Industrial Technology Development Organization (NEDO) Green Innovation Fund is being leveraged to speed up development.

Scientists from Syracuse University, South Dakota State University and Huzhou University have examined the use of polyaniline as a material for improved perovskite solar cells. The team demonstrated a facile, low-cost fabrication route for polyaniline hole transport mechanisms that display enhanced power conversion efficiency compared to conventional PEDOT:PSS hole transport layers in perovskites. This could provide a route toward low-cost, high-efficiency perovskite solar cells.

PEDOT:PSS is a commonly used material in perovskites, used as a hole transport layer between the photoactive perovskite layer and indium tin oxide layer. Using PEDOT:PSS improves the power conversion efficiency of perovskite solar cells. However, several issues have been observed with PEDOT:PSS. One of the fundamental issues is the degradation of active layers and defect formation associated with the large particle size of this material. Moreover, the use of this material as a hole transport layer is hindered by issues with low electrical conductivity limits and cost.

Researchers from Ulsan National Institute of Science and Technology (UNIST), Wuhan University of Technology and Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory have announced their success in manufacturing a high-efficiency, stable perovskite solar cell through a vacuum thin film deposition process.

Vacuum thin film deposition is a technique that is already widely used in the manufacture of large OLED TVs by evaporating raw materials in a vacuum and coating them thinly on a substrate. The perovskite solar cell developed this way displayed a photovoltaic-to-electricity conversion efficiency of 21.4%, which the team said is the highest among perovskite solar cells manufactured by vacuum thin film deposition process.

Researchers led by Prof. LIU Shengzhong from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) have developed a facile surface redox engineering (SRE) strategy for vacuum-deposited NiOx to match the slot-die-coated perovskite, and fabricated high-performance large-area perovskite submodules.

Inverted PSCs could be even more valuable than their normal counterparts because the former have easily-mitigated hysteresis behavior and long-term durability. NiOx has been demonstrated as a promising hole transport material for inverted PSCs. But for most vacuum-processed NiOx films, the relatively hydrophobic surface attenuates the adhesion of perovskite ink, making it challenging to deposit large-area perovskite films.

Researchers from the Karlsruhe Institute of Technology (KIT) and the Forschungszentrum Jülich GmbH in Germany have developed a monolithic perovskite-silicon solar cell with a power conversion efficiency of 20%, using a novel lamination approach.

The team investigated how this lamination process can be applied to perovskite/silicon tandem technology. They explained that the solar cells are the first prototypes and that lamination is a suitable alternative fabrication method for monolithic perovskite/silicon tandem solar cells. The lamination approach, they said, is particularly interesting for perovskite-based PV, as it notably increases the degree of freedom in the choice of materials and accessible deposition techniques.

Researchers from Switzerland's Federal Laboratories for Materials Science and Technology (EMPA) and École Polytechnique Fédérale de Lausanne (EPFL) have designed a four-terminal tandem mini-module based on perovskite and copper, indium, gallium and selenium (CIGS) with an aperture area of around 2 cm², and a geometric fill factor of over 93%.

Processing sequence of flexible NIR-transparent perovskite mini-module. Image from RRL Solar

The team reports that the key to efficient flexible perovskite-CIGS tandem modules is the development of near-infrared (NIR) transparent perovskite solar modules on a flexible polymer foil. To achieve these results, the researchers had to overcome the challenges of laser patterning on flexible substrates to realize the first all-laser scribed monolithically interconnected NIR-transparent perovskite mini-modules on polymer film. The perovskite mini-module used in the tandem panel was fabricated on a flexible polyethylene napthalathe (PEN) substrate mounted to a glass substrate in a p–i–n device architecture. This configuration, according to the research team, shows reduced absorption in the NIR region.

Researchers from the Eindhoven University of Technology, the Netherlands Organization for Applied Scientific Research (TNO), and Indian steel manufacturer Tata Steel recently fabricated an inverted perovskite solar cell based on a polymer-coated steel substrate that can achieve a power conversion efficiency approaching that of non-inverted reference solar cells with a similar stack design.

Substrate (A and B) and superstrate (C) p–i–n solar cells on glass (A and C) and steel (B). Image from ACS Publication study

The cell has a p-i-n structure and relies on nickel-plated steel coated with a polyamide-imide (PAI) planarization layer, which serves as an insulating layer. The researchers used an opaque titanium electrode covered with a thin sputtered indium tin oxide (ITO) layer to enable the binding of the phosphonic acid anchoring groups of the monolayer based on a perovskite known as 2PACz, which serves as a hole-collecting electrode.

Researchers from Ulsan National Institute of Science and Technology (UNIST) in South Korea and the University of Pittsburgh in the U.S have reported a power conversion efficiency of 23.5% in a perovskite-silicon tandem solar cell by applying a special textured anti-reflective coating (ARC) polymeric film.

The team prepared the multifunctional film with phosphor particles measuring 10 μm in diameter. They are able to block ultraviolet (UV) light and silicon dioxide (SiO₂) nanoparticles with a diameter of 10 nm to increase the ability of a perovskite-silicon tandem solar cell to absorb visible light. The scientists explained that the phosphors increase the reflectance of the ARC film, due to their large particle size, thus causing a backward light scattering issue. This in turn is compensated by the addition of the spherical SiO₂ nanoparticles.

TubeSolar, together with the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW), has reached an important milestone on the way to industrial production of its novel photovoltaic technology: an efficiency record of 14% was achieved on solar films in the industrially suitable "roll-to-roll" process. This was achieved as part of TubeSolar's perovskite research activities. 

In the process, the partners deposited all layers - with the exception of the front and rear contacts - using slot die. The speed of the coating process was over one metre per minute. The combination of this industrially suitable, fast production process and the high efficiency was referred to as 'groundbreaking' by the Companies. The flexible solar cells are used for the production of tubular photovoltaic modules, which can be used in agri-photovoltaics, among other applications.

Scientists from the University of Tokyo have reported a 26.2% power conversion efficiency for a four-terminal tandem solar cell based on perovskite and copper, indium, gallium and selenium (CIGS). The researchers said these results are a world record for such tandem solar devices and attributed the improvements to the performance of the perovskite top cell.

They built the 1-square-centimeter perovskite device using a transparent conductive material made of indium tin oxide (ITO), which was deposited via sputtering and without thermally evaporated Molybdenum oxides ( MoOx). “By eliminating the use of the MoOx buffer layer, we were able to develop semi-transparent PVK cells with higher durability and transmittance,” the scientists said.