Technical / research

Researchers from Germany's Karlsruhe Institute of Technology (KIT) have developed a scalable two-step evaporation and inkjet process for perovskite thin-film solar cells. The new technique is said to enable champion cells with the same efficiencies as those made with the spin coating process.

The process is described as a scalable and reliable technique for high-quality perovskite deposition, which combines the use of an evaporated lead iodide layer with inkjet-printed organic perovskite precursor materials. It is also said to exhibit high reproducibility and potential for conformal growth on textured silicon, and that provide films that are free of drying effects and toxic solvents.

Researchers from Korea's Daegu Gyeongbuk Institute of Science and Technology (DGIST), Ulsan National Institute of Science and Technology (UNIST) and Institute for Basic Science (IBS) recently developed high-performance, skin-attachable perovskite pure red light-emitting devices to create various forms of wearable displays.

The team developed these devices through selective surface modification of perovskite quantum dots, expecting their future use in diverse wearable products. As traditional red perovskite materials were unsuitable for high-performance wearable displays due to their low stability and electrical properties, the research team created pure red light-emitting devices through the simple surface modification of the perovskite light-emitting layers, thus significantly improving their stability and electrical properties.

Researchers from EPFL, Soochow University, Chinese Academy of Sciences, Lomonosov Moscow State University, Luxembourg Institute of Science and Technology (LIST), Julius Maximilian University of Würzburg, Toin University of Yokohama, Southern University of Science and Technology, Xi’an Jiaotong University, North China Electric Power University and Toyota Motor Europe recently developed a solar panel relying on EPFL's record-breaking 25.32%-efficient 2D/3D perovskite solar cells unveiled in July 2023.

The group's research demonstrates a larger surface area of 27.22 cm², achieving an impressive efficiency of 23.3%. In the paper, the scientists explain that the module's high efficiency was achieved thanks to a synergistic dopant-additive combination strategy aimed to improve the cell absorber's uniformity and crystallinity. They used, in particular, methylammonium chloride (MACl) as a dopant and a Lewis-basic ionic liquid known as 1,3-bis(cyanomethyl)imidazolium chloride ([Bcmim]Cl) as an additive.

Crystallization, the phenomenon that transforms disordered atoms or molecules into ordered solid-state structures, is an immensely studied process. However, while researchers have made significant strides in controlling the nucleation of crystals from precursor solutions, directing their subsequent growth to form defect-free single crystals with tailored shapes has proven far more challenging. This limitation has been particularly problematic for materials like halide perovskites, where controlling the formation of defects results in better photoelectric properties. Conventional techniques like inverse temperature crystallization or antisolvent vapor-assisted crystallization allow some control over average growth conditions, but their ability to pattern arbitrary single-crystal geometries while suppressing defect formation has remained confined.

Now, researchers at Tsinghua University have demonstrated optofluidic crystallithography (OCL), a novel approach that leverages a laser as a precise "pen" to simultaneously control the shape and quality of single-crystal halide perovskites as they grow from solution at record speeds.

Researchers from Malaysia have simulated a mixed cation solar cell based on a perovskite absorber integrating tin (Sn) and germanium (Ge) as mixed B cations. By modulating the perovskite layer thickness, they achieved an efficiency ranging of 24.25% - 31.49%.

Perovskite absorbers using mixed cations have the potential to improve stability, light absorption, and charge carrier mobility. A cations are used to control the bandgap and stability of the perovskite material, while B cations are intended to modify electrical and optical characteristics of perovskites. The scientists explained that using both elements in the B cation via “compositional engineering ” enables to reduce their respective defects and increase the cell performance, when compared to using each of them separately. Furthermore, the Ge atoms can replace Sn atoms in the perovskite crystal structure.

Researchers at UC Santa Barbara, Pusan National University and Korea Electric Power Research Institute have introduced a simple approach to produce high-quality perovskite films at room temperature by precisely regulating the perovskite composition with the addition of an organic linker (oleylamine, OAm). This work aims to address the challenge presented by current processes for manufacturing PSCs - that tend to rely on high-temperature annealing and intricate post-treatments.

The team’s innovation not only simplified the production process but also increased the material’s efficiency from under 20% to 24.4%. The method enabled phase conversion to the stable α-phase without thermal annealing, as confirmed by in situ X-ray monitoring. The optimized device achieved impressive efficiencies of 23.2% (24.4% with an anti-reflective coating), surpassing efficiencies attained by previous room/low-temperature-processed PSCs. 

Researchers from Wuhan University, University of South Florida, CNRS and Nanoneurosciences recently reported the first crystalline 2D Fullerene based Metal Halide Semiconductor, (C₆₀-2NH₃)Pb₂I₆.

Designing functionalized C60 adducts at the Spanopoulos Group at USF

According to the team, single crystal XRD studies elucidated the structure of the new material, while DFT calculations highlighted the strong contribution of C₆₀-2NH₃ to the electronic density of states of the conduction band of the material. Utilization of C₆₀-2NH₃ as an interlayer between a FA_0.6MA_0.4Pb_0.7Sn_0.3I₃ perovskite and a C60 layer reportedly offered superior band energy alignment, reduced nonradiative recombination, and enhanced carrier mobility.

Researchers from China's Shenzhen Campus of Sun Yat-sen University have reported a new type of two-terminal self-rectifying memristor that gets rid of asymmetric complex structures by using CsPbBr₃ perovskite nanocrystals (NCs). The integration of rectifying effects with resistance switching in a self-rectifying memristor offers the opportunity to suppress the sneak current in high-density crossbar arrays for energy-efficient neuromorphic computing.

This study demonstrates the possibility of constructing controllable self-rectifying memristors without involving asymmetric complex structures, paving a new way for resolving the sneak current issue in crossbar arrays of memristors. 

Researchers from Ulsan National Institute of Science and Technology (UNIST), Korea Electrotechnology Research Institute (KERI) and Sungkyunkwan University (SKKU) recently developed a straightforward and effective method for producing 3D architectures of perovskite quantum dot (PQD)-encapsulated high-performance composites (PQD-HPCs) through direct-ink writing (DIW). 

Schematic of the direct-ink writing (DIW) approach of luminescent PQD–polymer architectures. Image from Advanced Functional Materials

Led by Professor Im Doo Jung from the Department of Mechanical Engineering at UNIST, the recent study introduced a cutting-edge one-stop perovskite quantum dot (PQD) additive manufacturing technology. This approach eliminates the need for heat treatment, allowing for the creation of complex 3D shapes with exceptional precision, including iconic landmarks like the Eiffel Tower.

Researchers from Soochow University, Hunan University and Friedrich-Alexander University Erlangen-Nürnberg have incorporated pseudo-halogen thiocyanate (SCN) ions in iodide/bromide mixed halide perovskites and showed that they enhance crystallization and reduce grain boundaries. 

While perovskite/organic tandem solar cells could theoretically achieve high efficiency and stability, their performance is hindered by a process known as phase segregation, which degrades the performance of wide-bandgap perovskite cells and adversely affects recombination processes at the tandem solar cells' interconnecting layer. The team devised a strategy to suppress phase segregation in wide-bandgap perovskites, thus boosting the performance and stability of perovskite/organic tandem cells. This strategy entails the use of a pseudo-triple-halide alloy incorporated in mixed halide perovskites based on iodine and bromine.