Tremendous efforts have been devoted to developing thin film halide perovskites (HPs) for use in high‐performance photoelectronic devices, including solar cells, displays, and photodetectors. ...Furthermore, structured HPs with periodic micro‐ or nanopatterns have recently attracted significant interest due to their potential to not only improve the efficiency of an individual device via the controlled arrangement of HP crystals into a confined geometry, but also to technologically pixelate the device into arrays suitable for future commercialization. However, micro‐ or nanopatterning of HPs is not usually compatible with conventional photolithography, which is detrimental to ionic HPs and requires special techniques. Herein, a comprehensive overview of the state‐of‐the‐art technologies used to develop micro‐ and nanometer‐scale HP patterns, with an emphasis on their controlled microstructures based on top‐down and bottom‐up approaches, and their potential for future applications, is provided. Top‐down approaches include modified conventional lithographic techniques and soft‐lithographic methods, while bottom‐up approaches include template‐assisted patterning of HPs based on lithographically defined prepatterns and self‐assembly. HP patterning is shown here to not only improve device performance, but also to reveal the unprecedented functionality of HPs, leading to new research areas that utilize their novel photophysical properties.
Micro‐ and nanopatterned halide perovskites (HPs) have recently attracted significant attention due to their controllable photophysical properties and unprecedented photoelectronic functionalities. A comprehensive overview of the state‐of‐the‐art micro‐ and nanopatterning technologies based on top‐down lithography and bottom‐up self‐assembled structures is provided. The technological use of structured HPs is also discussed.
Soft ferroelectrics based on organic and organic–inorganic hybrid materials have gained much interest among researchers owing to their electrically programmable and remnant polarization. This allows ...for the development of numerous flexible, foldable, and stretchable nonvolatile memories, when combined with various crystal engineering approaches to optimize their performance. Soft ferroelectrics have been recently considered to have an important role in the emerging human‐connected electronics that involve diverse photoelectronic elements, particularly those requiring precise programmable electric fields, such as tactile sensors, synaptic devices, displays, photodetectors, and solar cells for facile human–machine interaction, human safety, and sustainability. This paper provides a comprehensive review of the recent developments in soft ferroelectric materials with an emphasis on their ferroelectric switching principles and their potential application in human‐connected intelligent electronics. Based on the origins of ferroelectric atomic and/or molecular switching, the soft ferroelectrics are categorized into seven subgroups. In this review, the efficiency of soft ferroelectrics with their distinct ferroelectric characteristics utilized in various human‐connected electronic devices with programmable electric field is demonstrated. This review inspires further research to utilize the remarkable functionality of soft electronics.
Owing to their electrically programmable remnant polarization, soft ferroelectrics have gained much interest, allowing the development of remarkable flexible photoelectronic devices with a built‐in electric field. A comprehensive review of the current progress of soft ferroelectric materials with an emphasis on their ferroelectric switching mechanisms and their potential application in human‐connected intelligent electronics is provided.
Spreading liquid droplets on solid surfaces is a core topic in physical chemistry with significant technological implications. Liquid metals, which are eutectic alloys of constituent metal atoms with ...low melting temperatures, are practically useful, but difficult to spread on solid surfaces because of their high surface tension. This makes it difficult to use liquid metals as deformable on‐board microcircuitry electrodes, despite their intrinsic deformability. In this study, it is discovered that eutectic gallium–indium (EGaIn) can be spread onto the surface of chemically cross‐linked hydrogels consisting of aliphatic alkyl chains with numerous hydroxyl groups (OH), thus facilitating the development of directly micropatterned EGaIn electrodes. More importantly, EGaIn patterned on a hydrogel autonomously reconciliates its surface to form a firm hydrogel interface upon mechanical deformation of the hydrogel. This autonomous surface reconciliation of EGaIn on hydrogels allows researchers to reap the benefits of chemically modified hydrogels, such as reversible stretching, self‐healing, and water‐swelling capability, thereby facilitating the fabrication of superstretchable, self‐healable, and water‐swellable liquid‐metal electrodes with very high conductance tolerance upon deformation. Such electrodes are suitable for a variety of deformable microelectronic applications.
Micropatternable, superstretchable, self‐healable, and water‐swellable liquid‐metal electrodes are developed with a low resistance of ≈2 and ≈4.6 Ω at strains of 0% and 1500%, respectively, with low variation in conductance (a variation factor of ≈2.3) by utilizing autonomous surface reconciliation of EGaIn on chemically modified hydrogels. These electrodes are suitable for a variety of deformable microelectronic applications.
The development of high-performance printable electrical circuits, particularly based on liquid metals, is fundamental for device interconnection in flexible electronics, motivating numerous attempts ...to develop a variety of alloys and their composites. Despite their great potential, rewritable and printable electronic circuits based on liquid metals are still manufactured on demand. In this study, we demonstrate liquid metal-based hydrogels suitable for rewritable, printable electrical circuits. Our liquid metal hydrogels are based on sedimentation-induced composites of eutectic gallium–indium (EGaIn) particles in poly(ethylene glycol) diacrylate (PEGDA). The EGaIn particles are vertically phase-segregated in the PEGDA. When a composite surface with high EGaIn content is gently scratched, the surface covering PEGDA is removed, followed by the rupture of the native oxide layers of the particles, and the exposed EGaIn becomes conductive. The subsequent water-driven swelling of PEGDA on the scratched surface completely erases the conductive circuit, causing the system to reset. Our friction-responsive liquid metal hydrogel exhibits writing–erasing endurance for 20 cycles, with a dramatic change in the electrical resistance from metal (∼1 Ω) to insulator (∼107 Ω). By employing surface friction pen printing, we demonstrate mechanically flexible, rewritable, printable electrical conductors suitable for displays.
Despite the excellent photoelectronic properties of the all‐inorganic cesium lead iodide (CsPbI3) perovskite, which does not contain volatile and hygroscopic organic components, only a few CsPbI3 ...devices are developed mainly owing to the frequent formation of an undesirable yellow δ‐phase at room temperature. Herein, it is demonstrated that a small quantity of poly(ethylene oxide) (PEO) added to the precursor solution effectively inhibits the formation of the yellow δ‐phase during film preparation, and promotes the development of a black α‐phase at a low crystallization temperature. A systematic study reveals that a thin, dense, pinhole‐free CsPbI3 film is produced in the α‐phase and is stabilized with PEO that effectively reduces the grain size during crystallization. A thin α‐phase CsPbI3 film with excellent photoluminescence is successfully employed in a light‐emitting diode with an inverted configuration of glass substrate/indium tin oxide/zinc oxide/poly(ethyleneimine)/α‐CsPbI3/poly(4‐butylphenyl‐diphenyl‐amine)/WO3/Al, yielding the characteristic red emission of the perovskite film at 695 nm with brightness, external quantum efficiency, and emission band width of ≈101 cd m−2, 1.12%, and 32 nm, respectively.
A small quantity of a poly(ethylene oxide) added in the precursor solution is beneficial for the development of all‐inorganic CsPbI3 perovskite in black α‐phase with significantly improved ambient stability. Dense, uniform, and pinhole‐free CsPbI3 thin films consisting of tens of nanometers black α‐phase crystals are successfully fabricated with excellent photophysical properties, leading to high performance light‐emitting diodes.
Zn‐polyiodide redox flow battery is considered to be promising energy storage systems. However, the rate of the I3−(aq)/I−(aq) half redox reaction could be limited by a metastable iodine film in ...aqueous solutions. In this article, we found that the addition of Br− could inhibit the formation of an iodine film (I2‐F) and form soluble I2Br−(aq) during the electrooxidation of I−. I− was electrochemically oxidized to the soluble form I3−(aq). The depletion of I−(aq) and an increase of I3−(aq) would lead to the formation of I2 and form I2‐F. Then, under a steady state, I−(aq) was electrochemically oxidized to I3−(aq) via I2‐F. However, the reaction pathway for the electrooxidation of I− was significantly altered by the addition of Br−. I− was electrochemically oxidized to I3−(aq) and was further oxidized to I2Br−(aq) without the formation of I2‐F. Moreover, we estimated the stability constant of I2Br−(aq) and consequently the fractional diagrams of I2(aq), I3−(aq), and I2Br−(aq) existing in a solution with both I− and Br− during the electrooxidation of I−, providing the necessity of a highly concentrated Br− condition in the vicinity of an electrode to form I2Br−(aq) as the main iodine species through the electrooxidation of I−.
Zn‐polyiodide redox flow battery is considered to be promising energy storage systems. Nevertheless, the overall battery performance could suffer from the rate of the triiodide/iodide half redox reaction due to in situ formation of a metastable iodine film in aqueous solution. In this article, we present that the addition of bromide could inhibit the formation of an iodine film and form soluble iodine bromide anion during the electro‐oxidation of iodide.
Development of a human-interactive display enabling the simultaneous sensing, visualisation, and memorisation of a magnetic field remains a challenge. Here we report a skin-patchable ...magneto-interactive electroluminescent display, which is capable of sensing, visualising, and storing magnetic field information, thereby enabling 3D motion tracking. A magnetic field-dependent conductive gate is employed in an alternating current electroluminescent display, which is used to produce non-volatile and rewritable magnetic field-dependent display. By constructing mechanically flexible arrays of magneto-interactive displays, a spin-patchable and pixelated platform is realised. The magnetic field varying along the z-axis enables the 3D motion tracking (monitoring and memorisation) on 2D pixelated display. This 3D motion tracking display is successfully used as a non-destructive surgery-path guiding, wherein a pathway for a surgical robotic arm with a magnetic probe is visualised and recorded on a display patched on the abdominal skin of a rat, thereby helping the robotic arm to find an optimal pathway.
The photocurrent conversions of transition metal dichalcogenide nanosheets are unprecedentedly impressive, making them great candidates for visible range photodetectors. Here we demonstrate a method ...for fabricating micron-thick, flexible films consisting of a variety of highly separated transition metal dichalcogenide nanosheets for excellent band-selective photodetection. Our method is based on the non-destructive modification of transition metal dichalcogenide sheets with amine-terminated polymers. The universal interaction between amine and transition metal resulted in scalable, stable and high concentration dispersions of a single to a few layers of numerous transition metal dichalcogenides. Our MoSe2 and MoS2 composites are highly photoconductive even at bending radii as low as 200 μm on illumination of near infrared and visible light, respectively. More interestingly, simple solution mixing of MoSe2 and MoS2 gives rise to blended composite films in which the photodetection properties were controllable. The MoS2/MoSe2 (5:5) film showed broad range photodetection suitable for both visible and near infrared spectra.
Since the working mechanism of triboelectric nanogenerators (TENGs) is based on triboelectrification and electrostatic induction, it is necessary to understand the effects of the inherent properties ...of dielectric materials on the performance of TENGs. In this study, the relationship between the relative permittivity and the performance of TENGs was demonstrated by fabricating TENGs using both pure oxide materials (SiO 2 , Al 2 O 3 , HfO 2 , Ta 2 O 5 and TiO 2 ) and oxide–PMMA composites. As oxide materials and PMMA are triboelectrically positive, PTFE film was selected as the counter tribo-material, which has highly negative triboelectric polarity. The triboelectric series of the above-mentioned oxides was experimentally organized to clarify the major parameter for the performance of TENGs. The electrical data values for both oxides and composites clearly showed a tendency to increase as the relative permittivity of the tribo-material increased. It is also well-matched with the theoretical analysis between the electrical performances ( e.g. open-circuit voltage) and relative permittivity. However, such a tendency is not observed with the triboelectric polarity. Due to the tribo-material’s high relative permittivity, an open-circuit voltage of 124.1 V, a short-circuit current of 14.88 μA and a power of 392.08 μW were obtained in a pure TiO 2 thin film.
Interactive displays involve the interfacing of a stimuli-responsive sensor with a visual human-readable response. Here, we describe a polymeric electroluminescence-based stimuli-responsive display ...method that simultaneously detects external stimuli and visualizes the stimulant object. This organic light-emitting board is capable of both sensing and direct visualization of a variety of conductive information. Simultaneous sensing and visualization of the conductive substance is achieved when the conductive object is coupled with the light emissive material layer on application of alternating current. A variety of conductive materials can be detected regardless of their work functions, and thus information written by a conductive pen is clearly visualized, as is a human fingerprint with natural conductivity. Furthermore, we demonstrate that integration of the organic light-emitting board with a fluidic channel readily allows for dynamic monitoring of metallic liquid flow through the channel, which may be suitable for biological detection and imaging applications.
PDF
