Technical / research - Page 24

Researchers from Nanjing University and University of Electronic Science and Technology of China have designed an all-perovskite tandem solar cell based on a wide bandgap perovskite top cell relying on a two-dimensional/three-dimensional heterostructure and a narrow bandgap bottom cell.

Schematic of the solar cell structure and the corresponding cross-sectional SEM image of an all-perovskite tandem solar cell. Image from Nature Communications

The research group used a generic 3D-to-2D perovskite conversion approach to fabricate the top cell. They first deposited a lead-halide perovskite (methylammonium lead iodide - MAPbI₃) layer by a hybrid evaporation/solution method and then transformed the layer into a 2D structure via a long-chain ammonium ligand.

Researchers at the Chinese Academy of Sciences (CAS), Peking University and  Soochow University have developed a polycrystalline silicon tunnelling recombination layer for perovskite/tunnel oxide passivating contact (TOPCon) silicon tandem solar cells (TSCs), which has reportedly achieved excellent efficiency and high stability.  

According to the team, previous efforts to increase device efficiency have mainly focused on improving the top sub-cell, leaving much room for improvement. The recombination layer, which serves as the electrical contact between the top and bottom sub-cells, plays a critical role in further efficiency progress. In this study, the researchers developed a polycrystalline silicon (poly-Si) tunnelling recombination layer that was incorporated into a perovskite/TOPCon silicon tandem cell. Through a two-step annealing strategy, the diffusion of boron and phosphorus dopants could be effectively restrained, granting the device excellent passivation and contact performance.

Researchers at Australia's University of Sydney, University of New South Wales, Macquarie University, Germany's Forschungszentrum Jülich, China's Southern University of Science and Technology ans Slovenia's University of Ljubljana have developed a perovskite-silicon solar cell design using a top perovskite PV device with an energy bandgap of 1.67 eV and a self-assembly monolayer based on carbazole. The tandem cell achieved a higher efficiency compared to counterparts without the monolayer and passed the IEC 61215 standard thermal cycling test.

The device is intended for applications as a top cell in perovskite-silicon tandem solar devices, where the upper cells must have a high energy bandgap to achieve output current matching. These top cells, however, suffer from a higher bandgap-voltage offset, due to non-radiative recombination and energetic misalignment between the perovskite and charge-selective layers. To address this issue, the team utilized a self-assembled monolayer (SAM) based on carbazole, which acts as an effective hole-selective layer (HSL). These SAMs were previously utilized in experimental solar cells and are commonly developed through a molecular glue added during processing in order to dramatically improve adhesion between the light-absorbing perovskite layer and the electron transport layer.

Researchers at China's Wuhan University assume that the practical use of all-perovskite tandem solar cells is hampered by the subpar performance and stability issues associated with mixed tin–lead (Sn–Pb) narrow-bandgap perovskite subcells. In their recent study, they focus on these narrow-bandgap subcells and develop an all-in-one doping strategy for them. 

The scientists introduce aspartate hydrochloride (AspCl) into both the bottom poly(3,4-ethylene dioxythiophene)–poly(styrene sulfonate) and bulk perovskite layers, followed by another AspCl posttreatment. They show that a single AspCl additive can effectively passivate defects, reduce Sn⁴⁺ impurities and shift the Fermi energy level. 

Researchers at the Chinese Academy of Sciences (CAS), Beijing Normal University, Beijing Institute of Technology and ShanghaiTech University have developed a universal hydrogen-bonding-facilitated DMA extraction method to fabricate high-quality γ-CsPbI3 films. The researchers fabricated a solar cell based on cesium-lead iodide (CsPbI₃) perovskite, which is also known as black perovskite.

The black perovskite solar cell reportedly achieved  20.25% efficiency, which is said by the team to be the highest efficiency reported for PV devices built with this perovskite material and a dopant-free hole transport layer based on the P3HT polymer. The cell was also able to retain around 93% of its original efficiency after continuous illumination for 570 h.

Researchers at China's Hefei Institutes of Physical Science (HIPS), University of Science and Technology of China (USTC), Southern University of Science and Technology (SUSTech), Hainan University, Germany's IEK5-Photovoltaics and University of Duisburg-Essen have proposed a strategy to enhance the performance of perovskite solar cells through the creation of a robust connection between different layers of the solar cell, using a molecular bridge made of ammonium cations.

The term 'fill factor' (FF) represents the capacity of a solar cell to deliver maximum current under optimal conditions. As limitations associated with FF still pose challenges, any advancements in this area are highly sought after. To address these limitations, the team focused on optimizing the bottom interface of the solar cell. They developed a strategy to redistribute localized electrostatic potential by employing ammonium cations as a molecular bridge with various degrees of substitution.

Researchers at Nanjing University and University of Illinois at Urbana-Champaign have drawn inspiration from the enhanced visual system of the Papilio xuthus butterfly, and developed an imaging sensor capable of “seeing” into the UV range inaccessible to human eyes. 

The design of the sensor uses stacked photodiodes and perovskite nanocrystals (PNCs) capable of imaging different wavelengths in the UV range. Using the spectral signatures of biomedical markers, such as amino acids, this new imaging technology is even capable of differentiating between cancer cells and normal cells with 99% confidence.

Researchers at the University of Missouri and the University of Tulsa have described a process using 3D printing to simplify the manufacturing of stable lighting technology. The work comes on the heels of the Biden administration’s recent decision to enforce a long-delayed rule banning the sale of most traditional incandescent light bulbs.

The team leveraged 3D printing to create resin-perovskite color conversion layers. Using an affordable 3D printer, they mixed perovskite nanocrystals capable of emitting green, yellow and red light with a transparent ultraviolet resin. The combination resulted in a thin color conversion layer that transformed UV light into various colors and demonstrated a high level of stability. The researchers then stacked these layers onto a UV light-emitting diode chip, producing a natural white light.

Perovskite nanocrystals (PNCs)/polymer nanocomposites can combine the advantages of both materials, but achieving the fabrication of PNCs/polymer nanocomposites by bulk polymerization has proven Very challenging. A team of scientists, led by Professor Bai Yang from Jilin University in China, has adopted a a two-type ligand strategy to fabricate bulk PNCs/polystyrene (PS) nanocomposites, including a new type of synthetic polymerizable ligand.

The CsPbCl₃ PNCs/PS nanocomposites reportedly showed extremely high transparency that can be ascribed to the Rayleigh scattering as the PNCs distribute uniformly without obvious aggregation. Based on this behavior, the team first exploited the potential of PNCs to serve as scatters inside light guided plate (LGP), whose surface illuminance and uniformity can be improved, and this new kind of LGP is compatible with advanced liquid crystal display technology. 

An international team that included scientists from the Chinese Academy of Sciences (CAS), Southern University of Science and Technology (SUSTech), University of Science and Technology of China (USTC), Sungkyunkwan University (SKKU), The Hong Kong University of Science and Technology, University Grenoble-Alpes, CEA, CNRS, INP, IRIG/SyMMES, IEK5-Photovoltaics and North China Electric Power University (NCEPU), has proposed a new method of fabricating homogenized perovskite films for solar cells. 

The process involves inhibiting phase segregation caused by internal cation inhomogeneity to increase conversion efficiency to 26.1%, thus tying the existing record.