Technical / research - Page 39

Scientists from Saudi Arabia’s King Abdullah University of Science and Technology (KAUST), Deutsches Elektronen-Synchrotron DESY, Academy of Sciences of the Czech Republic and Slovak Academy of Sciences have demonstrated a power conversion efficiency of 28.1% for a perovskite-silicon tandem solar cell based on textured silicon wafers.

Textured silicon wafers used in silicon solar cell manufacturing offer superior light trapping, which is a critical enabler for high-performance photovoltaics. The team explained that a similar optical benefit can be obtained in monolithic perovskite/silicon tandem solar cells, enhancing the current output of the silicon bottom cell. Yet, such complex silicon surfaces may affect the structural and optoelectronic properties of the overlying perovskite films.

Researchers from the University of Cambridge have developed a system that can transform plastic waste and greenhouse gases into sustainable fuels and other valuable products – using energy from the Sun. The team states that this is the first time that a system that can convert two waste streams into two chemical products at the same time has been achieved in a solar-powered reactor.

The reactor converts carbon dioxide (CO₂) and plastics into different products that are useful in a range of industries. In tests, CO₂ was converted into syngas, a key building block for sustainable liquid fuels, and plastic bottles were converted into glycolic acid, which is widely used in the cosmetics industry. The system can easily be tuned to produce different products by changing the type of catalyst used in the reactor. The integrated reactor, which uses a light absorber based on perovskites, has two separate compartments: one for plastic, and one for greenhouse gases. 

A research collaborative project involving scientists from Sweden's Karlstad University and Israel's Ben-Gurion University of the Negev and Weizmann Institute of Science will examine how perovskite solar cells could recover and self-repair at night.

Metal halide perovskite materials have been shown to possess a self-repairing ability. One of the Israeli research teams have shown that metal halide perovskite solar cells, which degrade in sunlight, can rebuild their efficiency at night, when it’s dark. The other Israeli research team exposed single crystals of lead-based metal halide perovskites to powerful lasers, which made them lose their ability to glow. The researchers then found that the material regained its photoluminescence following some recuperation time in darkness. Even if these two observations — one in the solar cell’s thin, multicrystalline layer and the other one in single crystals — seem related, the potential relation between these two phenomena still needs to be better understood, and how it works.

Researchers from Yonsei University, Sungkyunkwan University and Institute for Basic Science (IBS) have proposed a rapid crystallization method based on hot-antisolvent bathing for realization of deep-blue  perovskite light-emitting diodes (PeLEDs). The rapid crystallization method manipulates 2D perovskite phase evolution by controlling the crystallization kinetics for the fabrication of phase-pure 2D Ruddlesden‒Popper perovskites (2D-RPPs), enabling deep-blue-emissive perovskite LEDs.

PeLEDs are considered as promising candidates for next-generation solution-processed full-color displays. However, the external quantum efficiencies (EQEs) and operational stabilities of deep-blue (<460 nm) PeLEDs still lag far behind their red and green counterparts. 2D-RPPs have excellent optoelectronic properties—ideal for LEDs. Although 2D-RPP-based LEDs have rapidly progressed in terms of performance, it is still challenging to demonstrate blue-emissive and color-pure LEDs. The deep blue of current LED displays is usually produced by indium gallium nitride (InGaN), a costly substance. In the field of LEDs, researchers are seeking alternatives and one of them could be found in 2D-RPPs.

Researchers from the University of Minnesota Twin Cities-led, University of Wisconsin–Madison and Pacific Northwest National Laboratory have developed a new method for making thin films of perovskite oxide semiconductors, a class of “smart” materials with unique properties that can change in response to stimuli like light, magnetic fields, or electric fields. 

Their work could allow researchers to harness these properties and even combine them with other emerging nano-scale materials to make better devices such as sensors, smart textiles, and flexible electronics.

Researchers from Singapore's Nanyang Technological University have examined how thermal evaporation (TE) could be used to fabricate mini perovskite solar modules. TE are mature techniques that are commonly used in the microelectronic and optoelectronic industries to produce organic light-emitting diodes (OLEDs), metal contacts, and various coatings.

The research team analyzed the use of several evaporation-based techniques to fabricate halide perovskite thin films, from the relatively simple single-source deposition and multi-source co-evaporation to the more complex multistep evaporation and hybrids of thermal evaporation with gas reaction and solution processing. The team explained that this combined approach exploits the advantages of both methods, but also has some limitations, such as increased complexity and the use of solvents.

A team of researchers at EPFL have developed a method that improves both power conversion efficiency and stability of solar cells based on pure iodide as well as mixed-halide perovskites. The new method aslo suppresses halide phase segregation in the perovskite material. The research was carried out by the groups of Professors Michael Grätzel and Ursula Rothlisberger at EPFL and led by Dr Essa A. Alharbi and Dr Lukas Pfeifer.

The method treats perovskite solar cells with two alkylammonium halide modulators that work synergistically to improve solar cell performance. The modulators were used as passivators, compounds used to mitigate defects in perovskites, which are otherwise promoting the aforementioned degradation pathways.

Researchers at the National Renewable Energy Laboratory (NREL) and University of Toledo have developed a new approach to manufacturing perovskite solar cells.

Developing highly stable and efficient perovskites based on a rich mixture of bromine and iodine is considered critical for the creation of tandem solar cells. However, issues with the two elements separating under solar cell operational conditions, such as light and heat, limit the device voltage and operational stability. This challenge is often made worse by the ready defect formation associated with the rapid crystallization of bromine-rich perovskite chemistry with antisolvent processes.

Researchers from Japan's Teikyo University of Science and Toin University of Yokohama, under the JST Strategic Basic Research Program PRESTO, have developed a new near-infrared light sensor by using perovskite materials that convert weak near-infrared light to visible light.

Near-infrared light is used in a wide range of applications, such as in infrared cameras (night vision cameras), infrared communication (wireless communication), optical fiber communication, remote control, and biometric authentication. The detection of weak light in the near-infrared region and improvement of sensitivity are indispensable for the advancement in optical communication technology, medical diagnosis, environmental monitoring, and other fields. Compound semiconductors (e.g., InGaAs) having an optimal absorption band of 900–1700 nm, are used to detect light in the near-infrared region. However, these systems are expensive because of their complicated manufacturing process that involves the use of rare metals and is limited by noise interference. Moreover, such semiconductors do not exhibit visible light detection accuracy comparable to that achieved using silicon (Si) and other compounds.

Researchers from China's Jilin University have developed a promising method to fabricate white perovskite LEDs using lanthanides (Ln³⁺) ions doped CsPbCl₃ perovskite nanocrystals (PeNCs).

Lead halide perovskite nanocrystals (PeNCs) have attracted extensive attention due to their high photoluminescence quantum yield (PLQY), adjustable bandgap, low cost, and excellent photoelectric properties. In recent years, perovskite based light emitting diodes (LEDs) have developed rapidly and become candidates for low-cost, solution-processing based solid-state lighting. White light perovskite LEDs are possible to be obtained by stacking different NCs with complementary emissions together in one film. However, the halide ion segregation and exchange lead to severe color instability and complex structure in mixed halide perovskite LED devices. Therefore, new technologies are required for the development of white light devices.