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Researchers led by the University of Rochester claim to have increased the photoresponsivity of a lead-halide perovskite for solar cell applications by 250%. They created a perovskite film with a plasmonic substrate made of hyperbolic metamaterial and characterized it with transition dipole orientation.

Scientists led by the University of Rochester in New York state have considerably reduced electron recombination processes in lead-halide perovskites (LHPs) used for solar cell applications. Recombination can have a significant impact on electrical performance in perovskite cells, with implications for open-circuit voltage, short-circuit current, fill factor, and ultimately, power conversion efficiency.

The researchers used what they call a “physics-based method” to create a film based on a type of LHP known as methylammonium lead iodide (MAPbI3). They deposited that directly on a plasmonic substrate made of hyperbolic metamaterial (HMM) with a high local density of state, via spin coating. They fabricated the multi-layered HMM with four pairs of alternative 10 nm thick layers made of silver, aluminum sulfate, and ozone (Ag-Al2 O3) by electron beam evaporation.

“The metal layer serves as a mirror, which creates reversed images of electron-hole pairs, weakening the ability of the electrons to recombine with the holes,” the scientists said, noting that they used a momentum-resolved imaging technique to characterize the film’s transition dipole orientation, which is the key factor enabling control over exciton recombination processes.

They claim that the interaction between the in–plane dipole of the LHP and its image formed on plasmonic substrate results in a tenfold decrease in the recombination rate, without any chemical treatment, optical cavity, and photonic band–gap engineering.

“Furthermore, image dipole interaction enables us to substantially improve the device performance of photodetectors by achieving more than 250% increase in the photoresponsivity,” they added.

The academics presented their findings in “Gigantic suppression of recombination rate in 3D lead-halide perovskites for enhanced photodetector performance,” which was recently published in Nature Photonics.

An all-solution based cesium lead halide perovskite patterning process with adjustable phases and optical properties is reported. With the patterning process, the high-resolution photodetector array and luminescent patterns are demonstrated. The perovskite patterning process enables the integration of perovskites into image sensors and displays.

Abstract

Perovskite has been actively studied for optoelectronic applications, such as photodetectors and light-emitting diodes (LEDs), because of its excellent optoelectronic properties. However, ionic bonds of the perovskite structure are vulnerable to chemicals, which makes perovskite incompatible with photolithography processes that use polar solvents. Such incompatibility with photolithography hinders perovskite patterning and device integration. Here, an all-solution based cesium lead halide perovskite (Cs _x Pb _y Br _z ) patterning method is introduced in which PbBr₂ is patterned and then synthesized into Cs _x Pb _y Br _z . Each step of the top-down patterning process (e.g., developing, etching, and rinsing) is designed to be compatible with existing photolithography equipment. Structural, chemical, and optical analyses show that the PbBr₂ pattern of (10 µm)² squares is successfully transformed into CsPbBr₃ and Cs₄PbBr₆ with excellent absorption and emission properties. High-resolution photoconductor arrays and luminescent pattern arrays are fabricated with CsPbBr₃ and Cs₄PbBr₆ on various substrates, including flexible plastic films, to demonstrate their potential applications in image sensors or displays. The research provides a fundamental understanding of the properties and growth of perovskite and promotes technological advancement by preventing degradation during the photolithography process, enabling the integration of perovskite arrays into image sensors and displays.

The octylammonium sulfate decoration effectively enhances the moisture durability of PEA_0.4CsPbBr_3.4 quasi-2D perovskite film by the generated PbSO₄ on the surface. The strong bonding interaction of SO₄ ²⁻ and Pb²⁺ ions leads to reduced defect density, enhanced lattice stability, and robust PLQY of perovskite film.

Abstract

Quasi-2D perovskite exhibits excellent luminescence properties for highly efficient perovskite light-emitting diodes (PeLEDs). However, the lattice degradation and crystalline phase transition induced by water limit the PeLED's development for application and commercialization. It is demonstrated that the organic additives effectively reduce the defect density, while the bonding strength of these organics and perovskite becomes weak under the high electric field and the Joule heat in an operating PeLED. Thus, an alternative additive for forming strong bonding with perovskite is promising to improve the stability of perovskite film and PeLEDs simultaneously. Here, it is shown that octylammonium sulfate decoration effectively enhances the moisture durability of PEA₂(CsPbBr₃)₄PbBr₄ quasi-2D perovskite film by generating PbSO₄ on the surface. The strong bonding interaction of SO₄ ²⁻ and Pb²⁺ ions leads to the reduced defect density, enhanced lattice stability, and robust photoluminescence quantum yield of perovskite film, which is confirmed by the density functional theory calculation. Moreover, the generated PbSO₄ reduces the internal resistance and adjusts the band structure of perovskite film to enhance the carrier transport and injection balance. The PeLEDs based on PbSO₄ decorated perovskite film exhibit enhanced operational lifetime and the maximum external quantum efficiency of 10.84%.

Platelet‐targeting bispecific antibodies (PT‐BsAbs) are designed to recognize hematopoietic stem cells (HSCs) and platelets simultaneously in the lung. Due to the innate injury‐finding ability of platelets, inhaled PT‐BsAbs guide lung HSCs to the injured heart for cardiac repair.

Abstract

Stem cell therapy is a promising strategy for cardiac repair. However, clinical efficacy is hampered by poor cell engraftment and the elusive repair mechanisms of the transplanted stem cells. The lung is a reservoir of hematopoietic stem cells (HSCs) and a major biogenesis site for platelets. A strategy is sought to redirect lung resident stem cells to the injured heart for therapeutic repair after myocardial infarction (MI). To achieve this goal, CD34‐CD42b platelet‐targeting bispecific antibodies (PT‐BsAbs) are designed to simultaneously recognize HSCs (via CD34) and platelets (via CD42b). After inhalation delivery, PT‐BsAbs reach the lungs and conjoined HSCs and platelets. Due to the innate injury‐finding ability of platelets, PT‐BsAbs guide lung HSCs to the injured heart after MI. The redirected HSCs promote endogenous repair, leading to increased cardiac function. The repair mechanism involves angiomyogenesis and inflammation modulation. In addition, the inhalation route is superior to the intravenous route to deliver PT‐BsAbs in terms of the HSCs’ homing ability and therapeutic benefits. This work demonstrates that this novel inhalable antibody therapy, which harnesses platelets derived from the lungs, contributes to potent stem cell redirection and heart repair. This strategy is safe and effective in a mouse model of MI.