Technical / research

Researchers from China's Kunming University of Science and Technology and Southwest United Graduate School have doped rare-earth ions into borosilicate glass for the first time to induce the self-crystallization of CsPbBr₃ QDs.

All-inorganic perovskite quantum dots (QDs) in glass materials, specifically CsPbX₃ (X = Cl, Br, I), have potential as next-generation fluorescent materials due to their impressive luminous performance and stability. However, the crystallization process of quantum dots within the glass presents a challenge, leading to uneven crystallinity and subsequent reductions in light efficiency, thereby affecting practical applications. In glass ceramics doped with rare-earth oxides, the introduction of rare-earth ions as nucleating agents can promote the self-precipitation of nanocrystalline crystals within the glass. 

Researchers from the University of Stuttgart, Lawrence Berkeley National Laboratory and Brandenburg University of Technology Cottbus-Senftenberg have introduced a simplified deposition procedure for multidimensional (2D/3D) perovskite thin films, integrating a phenethylammonium chloride (PEACl)-treatment into the antisolvent step when forming the 3D perovskite. 

The “traditional” deposition and passivation processes (top row) and the integrated deposition and passivation strategy to form 2D passivated 3D halide perovskite films (bottom row). Image from Advanced Materials.

This recently developed simultaneous deposition and passivation strategy reduces the number of synthesis steps while simultaneously stabilizing the halide perovskite film and improving the photovoltaic performance of resulting solar cell devices to 20.8%. 

Researchers at Austria's Johannes Kepler University Linz have developed lightweight, thin (<2.5 μm), flexible and transparent-conductive-oxide-free quasi-two-dimensional perovskite solar cells by incorporating alpha-methylbenzyl ammonium iodide into the photoactive perovskite layer. 

The team fabricated the devices directly on an ultrathin polymer foil coated with an alumina barrier layer to ensure environmental and mechanical stability without compromising weight and flexibility. 

Researchers from Helmholtz-Zentrum Berlin (HZB) and the University of Potsdam have analyzed surfaces and interfaces of CsPbI₃ films, produced under different conditions, at BESSY II. They found that annealing in ambient air does not have an adverse effect on the optoelectronic properties of the semiconductor film, but actually results in fewer defects. This could simplify the mass production of inorganic perovskite solar cells.

The best performing perovskite semiconductors contain organic cations such as methylammonium, which cannot tolerate high temperatures and humidity, so their long-term stability is still a challenge. However, methylammonium can be replaced by inorganic cations such as Cesium (Cs). Inorganic halide perovskites with the molecular formula CsPbX₃ (where X stands for a halide such as chloride, bromide and iodide) remain stable even at temperatures above 300 °C. CsPbI₃ has the best optical properties for photovoltaics (band gap ∼1.7 eV).

Researchers at NREL, BlueDot Photonics, University of Washington, Colorado School of Mines and Rochester Institute of Technology have developed a vapor deposition technique based on continuous flash sublimation (CFS) to fabricate all-inorganic perovskite thin films in under 5 minutes in a continuous process. The adoption of the proposed approach may also result in higher power conversion efficiencies of perovskite solar cell.

Schematic illustration of the continuous flash sublimation (CFS) approach consisting of a mechano-chemical synthesis of the source powder (here CsPb(I_xBr_1−x)₃), the high-throughput deposition process in a home-made evaporation system, and a short post-annealing treatment to improve thin-film quality. Image from Journal of Materials Chemistry A

The team described the new technique as a non-batch process that solves two problems associated with the use of established vapor processing in perovskite material manufacturing – the slow speed of deposition and the non-continuous nature of batch processing.

Scalable deposition of high-efficiency perovskite solar cells (PSCs) is vital to achieving commercialization. However, a significant number of defects are distributed at the buried interface of perovskite film fabricated by scalable deposition, which adversely affects the efficiency and stability of PSCs. Now, researchers at China's Central South University, Hunan Institute of Engineering and  Chinese Academy of Sciences (CAS) addressed this issue by incorporating 2-(N-morpholino)ethanesulfonic acid potassium salt (MESK) as the bridging layer between the tin oxide (SnO₂) electron transport layer (ETL) and the perovskite film deposited via scalable two-step doctor blading. 

The scientists reported that both experiment and simulation results demonstrated that MESK can passivate the trap states of Sn suspension bonds, thereby enhancing the charge extraction and transport of the SnO₂ ETL. 

Researchers at Korea University, Kyungpook National University, Hanyang University, Dongguk University and Mississippi State University have used a novel ligand passivation strategy in perovskite quantum dots (PQDs) photovoltaics (PQDPVs) to enhance the carrier lifetime. 

The advancement of perovskite photovoltaic (PePV) systems for harnessing indoor light energy has been accelerated by the advent of the Internet of Things (IoT). However, the commercialization of these systems is impeded by moisture instability and restricted carrier lifetimes. Perovskite quantum dots (PQDs) offer viable solutions for increasing stability despite the potential effects of their organic ligands on efficiency. 

Researchers from Northwestern University, University of Toronto, ShanghaiTech University, University of Victoria and Arizona State University have developed highly stable, highly efficient 0.05cm² perovskite solar cell with a PCE of 26.15%, certified by a National Renewable Energy Laboratory-accredited facility. The team said that the prior certified world record published in a scientific journal was 25.73%.

A 1.04 cm² device had a certified power conversion efficiency of 24.74%, also a record for its size. The best devices retained 95% of their initial PCE following 1,200 hours of continuous solar illumination at a temperature of 65 degrees.

Researchers at Linköping University, Nanjing University and NanjingTech have developed a multifunctional display that uses photo-responsive metal halide perovskite LEDs as pixels. The perovskite LED display can be simultaneously used as a touch screen, ambient light sensor and image sensor (including for fingerprint drawing) without integrating any additional sensors. The light-to-electricity conversion efficiency of the pixels also allow the display to act as a photovoltaic device that can charge the equipment.

Illustration of functions realized by the multifunctional display. Image from Nature Electronics

This is a step forward compared to current display screens, which are typically only used for information display, but can have a range of different sensors integrated into them for functions such as touch control, ambient light sensing and fingerprint sensing. According to the team, photo-responsive light-emitting diodes (LEDs), which can display information and respond to light excitation, could be used to develop future ultra-thin and large screen-to-body ratio screens. However, photo-response is difficult to achieve with conventional display technologies. 

Researchers from the University of Freiburg and Fraunhofer ISE recently put together a roadmap for the optical properties of perovskite/perovskite/silicon triple-junction cells. They investigated the optical properties of perovskite/perovskite/silicon triple-junction cells and found these devices may have a practical efficiency potential of 44.3% assuming idealized electrical parameters. These cells may also potentially achieve a fill factor of 90.1%.

The group of researchers developed a comprehensive optoelectrical simulation model for triple-junction solar cells based on subcells relying on perovskite, perovskite, and crystalline silicon, respectively. The model aims to define an efficiency roadmap for improving the optical properties of these solar cells within realistic boundary conditions.