Technical / research - Page 32

Researchers from Stanford University have reported a novel way to improve the performance of perovskite light-emitting diodes (PeLEDs) in the violet region. The new method could represent a promising step toward cost-effective and efficient ultraviolet PeLEDs.

By engineering the crystallization process of spin-coated 2D perovskites with water, the resulting PeLEDs exhibit bright violet emission at 408 nm with an external quantum efficiency of 0.41%, a 5-fold increase over control devices. 

Researchers from China's Fudan University, Central South University, East China Normal University, Chinese Academy of Sciences and Suzhou University of Science and Technology, along with Canada's University of Victoria and Austria's University of Vienna, have proposed a novel strategy to achieve efficient and stable perovskite solar cells (PSCs) through introducing bis-diazirine molecules to immobilize the organic cations by covalent bonds.

The resulting PSCs exhibited a high certified efficiency of over 24% with long operational stability of over 1,000 hours. The scientists believe that this strategy also possesses great potential in other perovskite-based optoelectronic devices. 

Researchers from the University of North Carolina at Chapel Hill, University of Toledo and Perotech Energy have found that bathocuproine, which is often used as an electron-transport material, can improve power-conversion efficiency and stability when added to the hole-transport layer. 

The chelation product of bathocuproine with lead ions is insoluble in the perovskite ink and also decreases the formation of amorphous regions by reducing the amount of trapped dimethyl sulfoxide solvent. Minimodules with an aperture area of 26.9 square centimeters had a certified efficiency of 21.8% and light-soaking stability exceeding 2000 hours. 

Researchers from the University of Science and Technology of China and Dongguan University of Technology have found a way to improve perovskite solar cells by adding a layer that improves stability and efficiency at capturing power from sunlight.

All-inorganic perovskite solar cells are more stable at high temperatures, which is important for their long-term performance. However, they are not as efficient at converting sunlight into electricity compared to solar cells made with a mix of organic and inorganic materials. The team explored the use of an additional layer to fix the issues found in all-inorganic perovskite solar cells. In these solar cells, the layers of the perovskite material tend to encounter problems with their structure, energy levels, and electron traps. These issues reduce the movement of electrons and overall efficiency of the solar cell. To address these problems, the scientists introduced an extra layer called bis-dimethylamino-functionalized fullerene derivative (PCBDMAM) between the perovskite layer and the layer that helps with electron transport. This interlayer improves the movement of electrons and increases the solar cell's efficiency, while also enhancing its stability at different temperatures.

University of Cambridge researchers have used perovskites to develop a solar-powered technology that converts carbon dioxide and water into liquid fuels that can be added directly to a car’s engine as drop-in fuel.  

The researchers relied on photosynthesis to convert CO₂, water and sunlight into multicarbon fuels – ethanol and propanol – in a single step. These fuels have a high energy density and can be easily stored or transported.

Researchers fromKorea's Pohang University of Science and Technology (POSTECH), Ajou University, Daegu Gyeongbuk Institute of Science and Technology (DGIST) and Kookmin University have designed new polymeric hole transport materials that constitute a crucial element in perovskite quantum dot solar cells, leading to significant increase in their efficiency. 

The team's hole transport materials include polymers based on sulfur and selenium compounds. These polymers exhibit structural features, such as planarization and locking of intermolecular arrangements, which increase charge mobility. Furthermore, asymmetric alkyl substituents of the polymers facilitate molecular interactions, thereby complementing the electrical properties of cells.

Scientists from the Nanjing University of Aeronautics and Astronautics in China and University of Okara in Pakistan have simulated a solar cell based on an absorber using a CsSnI₃ perovskite material, which is an inorganic perovskite that has low exciton binding energy, a high absorbance coefficient, and an energy bandgap of 1.3 eV.

The researchers used the SCAPS-1D solar cell capacitance software, which is a simulation tool for thin-film solar cells developed by the University of Ghent in Belgium, to simulate several cell designs with different electron transport layers (ETLs) and hole transport layers (HTLs). Through a series of simulations, the team found that the best possible cell configuration was provided by a device based on a substrate made of fluorine-doped tin oxide (FTO), a titanium oxide (TiO₂) ETL, the CsSnI₃ absorber, an HTL based on nickel(II) oxide (NiOx), and back electrodes.

Researchers from China's Henan University and Chinese Academy of Sciences (CAS) have reported an extremely efficient carbon electrode perovskite solar cell that reportedly achieves a power conversion efficiency of 20.8% while providing enhanced stability.

Schematic diagram of the fabrication process of bilayer HTL carbon electrode perovskite solar cells. Image from the study published in Journal of Materials Research and Technology

Commonly used metal contact electrodes can promote the degradation of perovskite solar cells due to the diffusion of metal impurities across the interfaces. This issue could be theoretically overcome by replacing the metal contact with carbon electrodes, which are highly promising for commercialization due to their ambient pressure processability based on industrially established printing techniques. The problem is, however,  that perovskite solar cells based on carbon electrodes lead to performance losses at the point where the carbon electrode meets the perovskite layer.

Researchers from the University of North Carolina at Chapel Hill have reported bifacial minimodules with front efficiency comparable to opaque monofacial counterparts, while gaining additional energy from albedo light. Their new design strategy could help to improve the efficiency and stability of bifacial perovskite solar cells. 

The scientists added a hydrophobic additive to the hole transport layer to protect the perovskite films from moisture. They also integrated silica nanoparticles with proper size and spacing in perovskite films to recover the absorption loss induced by the absence of reflective metal electrodes. The small-area single-junction bifacial perovskite cells achieved a power-generation density of 26.4 mW cm⁻² under 1 sun illumination and an albedo of 0.2. The bifacial minimodules showed front efficiency of over 20% and bifaciality of 74.3% and thus a power-generation density of over 23 mW cm⁻² at an albedo of 0.2. The bifacial minimodule retained 97% of its initial efficiency after light soaking under 1 sun for over 6,000 hours at 60 ± 5 °C.

Researchers from the National University of Singapore (NUS), led by Professor Liu Xiaogang from the Department of Chemistry, have developed a perovskite-based 3D imaging sensor that has an extremely high angular resolution, which is the capacity of an optical instrument to distinguish points of an object separated by a small angular distance, of 0.0018o. This innovative sensor operates on a unique angle-to-colour conversion principle, allowing it to detect 3D light fields across the X-ray to visible light spectrum.  

 Design of the 3D light-field sensor on the basis of pixelated color conversion. Image from study 

A light field encompasses the combined intensity and direction of light rays, which the human eyes can process to precisely detect the spatial relationship between objects. Traditional light sensing technologies, however, are less effective. Most cameras, for instance, can only produce two-dimensional images, which is adequate for regular photography but insufficient for more advanced applications, including virtual reality, self-driving cars, and biological imaging. These applications require precise 3D scene construction of a particular space.