Delayed Triplet-State Formation through Hybrid Charge Transfer Exciton at Copper Phthalocyanine/GaAs Heterojunction

Light absorption in organic molecules on an inorganic substrate and subsequent electron transfer to the substrate create so-called hybrid charge transfer exciton (HCTE). The relaxation process of the HCTE states largely determines charge separation efficiency or optoelectronic device performance. Here, the study on energy and time-dispersive behavior of photoelectrons at the hybrid interface of copper phthalocyanine (CuPc)/<i>p</i>-GaAs­(001) upon light excitation of GaAs reveals a clear pathway for HCTE relaxation and delayed triplet-state formation. According to the ground-state energy level alignment at the interface, CuPc/<i>p</i>-GaAs­(001) shows initially fast hole injection from GaAs to CuPc. Thus, the electrons in GaAs and holes in CuPc form an unusual HCTE state manifold. Subsequent electron transfer from GaAs to CuPc generates the formation of the triplet state in CuPc with a few picoseconds delay. Such two-step charge transfer causes delayed triplet-state formation without singlet excitation and subsequent intersystem crossing within the CuPc molecules

Highly Stable Cesium Lead Halide Perovskite Nanocrystals through in Situ Lead Halide Inorganic Passivation

Highly Stable Cesium Lead Halide Perovskite Nanocrystals through in Situ Lead Halide Inorganic Passivatio

Photovoltaic Performance and Interface Behaviors of Cu(In,Ga)Se₂ Solar Cells with a Sputtered-Zn(O,S) Buffer Layer by High-Temperature Annealing

We selected a sputtered-Zn­(O,S) film as a buffer material and fabricated a Cu­(In,Ga)­Se₂ (CIGS) solar cell for use in monolithic tandem solar cells. A thermally stable buffer layer was required because it should withstand heat treatment during processing of top cell. Postannealing treatment was performed on a CIGS solar cell in vacuum at temperatures from 300–500 °C to examine its thermal stability. Serious device degradation particularly in <i>V</i>_<i>OC</i> was observed, which was due to the diffusion of thermally activated constituent elements. The elements In and Ga tend to out-diffuse to the top surface of the CIGS, while Zn diffuses into the interface of Zn­(O,S)/CIGS. Such rearrangement of atomic fractions modifies the local energy band gap and band alignment at the interface. The notch-shape induced at the interface after postannealing could function as an electrical trap during electron transport, which would result in the reduction of solar cell efficiency

Ultrathin and Flat Layer Black Phosphorus Fabricated by Reactive Oxygen and Water Rinse

Ultrathin black phosphorus (BP) is one of the promising two-dimensional (2D) materials for future optoelectronic devices. Its chemical instability in ambient conditions and lack of a bottom-up approach for its synthesis necessitate efficient etching methods that generate BP films of designed thickness with stable and high-quality surfaces. Herein, reporting a photochemical etching method, we demonstrate a controlled layer-by-layer thinning of thick BP films down to a few layers or a single layer and confirm their Raman and photoluminescence characteristics. Ozone molecules generated by O₂ photolysis oxidize BP, forming P₂O₅-like oxides. When the resulting phosphorus oxides are removed by water, the surface of BP with preset thickness is highly flat and self-protective by surface oxygen functional groups. This method provides a fabrication strategy of BP and possibly other 2D semiconductors with band gaps tuned by their thickness

Simulated-Sunlight-Driven Cell Lysis of Magnetophoretically Separated Microalgae Using ZnFe₂O₄ Octahedrons

In an effort to help meet the demand for promising renewable sources of energy, research into innovative downstream processing for microalgae biorefineries is actively underway. In the current work, we used octahedrally shaped ZnFe₂O₄ nanoparticles for both harvesting and disrupting the cells of microalgae. We were able to use ZnFe₂O₄ octahedrons as magnetic flocculants and cell-disruption agents because ZnFe₂O₄ nanoparticles have both magnetic and photocatalytic properties. The ZnFe₂O₄ octahedrons, when simply functionalized with the aminosilane N-[3-(trimethoxysilyl)­propyl] ethylenediamine, enabled a rapid and energy-efficient harvesting of microalgae. Furthermore, the ZnFe₂O₄ octahedrons, well-known for having photocatalytic properties superior to those of ZnFe₂O₄ nanoparticles with other morphologies, were used to lyse the algal cell wall with the aid of H₂O₂ under simulated sunlight irradiation. We expect microalgae whose cells can be both magnetophoretically separated and lysed by the same ZnFe₂O₄ nanoparticles to be utilized as bioenergy resources for more efficient downstream processing than is currently available

Recovery of Corneal Endothelial Cells from Periphery after Injury

<div><p>Background</p><p>Wound healing of the endothelium occurs through cell enlargement and migration. However, the peripheral corneal endothelium may act as a cell resource for the recovery of corneal endothelium in endothelial injury.</p><p>Aim</p><p>To investigate the recovery process of corneal endothelial cells (CECs) from corneal endothelial injury.</p><p>Methods</p><p>Three patients with unilateral chemical eye injuries, and 15 rabbit eyes with corneal endothelial chemical injuries were studied. Slit lamp examination, specular microscopy, and ultrasound pachymetry were performed immediately after chemical injury and 1, 3, 6, and 9 months later. The anterior chambers of eyes from New Zealand white rabbits were injected with 0.1 mL of 0.05 N NaOH for 10 min (NaOH group). Corneal edema was evaluated at day 1, 7, and 14. Vital staining was performed using alizarin red and trypan blue.</p><p>Results</p><p>Specular microscopy did not reveal any corneal endothelial cells immediately after injury. Corneal edema subsided from the periphery to the center, CEC density increased, and central corneal thickness decreased over time. In the animal study, corneal edema was greater in the NaOH group compared to the control at both day 1 and day 7. At day 1, no CECs were detected at the center and periphery of the corneas in the NaOH group. Two weeks after injury, small, hexagonal CECs were detected in peripheral cornea, while CECs in mid-periphery were large and non-hexagonal.</p><p>Conclusions</p><p>CECs migrated from the periphery to the center of the cornea after endothelial injury. The peripheral corneal endothelium may act as a cell resource for the recovery of corneal endothelium.</p></div

Photochemical Hydrogen Doping Induced Embedded Two-Dimensional Metallic Channel Formation in InGaZnO at Room Temperature

The photochemical tunability of the charge-transport mechanism in metal-oxide semiconductors is of great interest since it may offer a facile but effective semiconductor-to-metal transition, which results from photochemically modified electronic structures for various oxide-based device applications. This might provide a feasible hydrogen (H)-radical doping to realize the effectively H-doped metal oxides, which has not been achieved by thermal and ion-implantation technique in a reliable and controllable way. In this study, we report a photochemical conversion of InGaZnO (IGZO) semiconductor to a transparent conductor via hydrogen doping to the local nanocrystallites formed at the IGZO/glass interface at room temperature. In contrast to thermal or ionic hydrogen doping, ultraviolet exposure of the IGZO surface promotes a photochemical reaction with H radical incorporation to surface metal–OH layer formation and bulk H-doping which acts as a tunable and stable highly doped n-type doping channel and turns IGZO to a transparent conductor. This results in the total conversion of carrier conduction property to the level of metallic conduction with sheet resistance of ∼16 Ω/□, room temperature Hall mobility of 11.8 cm² V^–1 sec^–1, the carrier concentration at ∼10²⁰ cm^–3 without any loss of optical transparency. We demonstrated successful applications of photochemically highly n-doped metal oxide via optical dose control to transparent conductor with excellent chemical and optical doping stability

Photographs of anterior segments (A) and central corneal thickness data (CCT; B).

<p>A. Chemical injury of the cornea causes severe corneal edema and endothelial damage immediately after chemical injury. Slit lamp examination shows severe edematous and opaque cornea, and Descemet’s membrane folds. Endothelial cells are absent under specular microscopy. Corneal edema is reduced from the periphery to the center over time. Case 1 shows severe corneal edema and Descemet’s membrane fold immediately after injury, central edema and peripheral transparency 1 month after injury, and a clear cornea 6 months after injury. Case 2 shows severe corneal edema and Descemet’s membrane folds immediately after injury; the cornea becomes more transparent from periphery 1 month after injury. Case 3 shows severe corneal edema and Descemet’s membrane folds immediately after injury and the cornea becoming clear from the periphery 1 month after injury. This case also shows transparency of the central edema and periphery 6 months after injury. B. CCT is greater immediately after injury but decreases significantly 6 and 9 months later (p = 0.014 and 0.012, respectively, paired t-test) * Statistically significant by paired t-test</p

Evaluation of corneal endothelial cells using specular microscopy.

<p>A. Corneal endothelial cells are absent immediately after chemical injury; however, they are present 3 months (case 2) or 6 months (case 1 and case 3) later. B. CECD increased significantly 6 months following injury compared to immediately and 1 month after injury (p = 0.008 and p = 0.008, respectively, paired t-test), and 9 months after injury compared to those immediately or 1 months after injury (p = 0.005 and p = 0.005, respectively, paired t-test). C. Average cell area generally decreases over time, although not significantly. D. CV does not change and hexagonal cells are absent 3 to 9 months after injury. * Statistically significant by paired t-test</p

Changes in corneal edema and opacity after chemical corneal endothelial injury in rabbits.

<p>A. Corneal edema increases 1 day after injury compared to the control, and then decreases over time; however, corneal opacity does not revert back to levels observed in control rabbits at day 14. Corneal edema decreases from the periphery, and peripheral and central corneas are edematous at day 1 and at day 7. At day 14, the central cornea is edematous (white arrow), while the periphery is transparent (black arrow). B. CCT increases significantly at day 1 and at day 7 after injury compared to the control (p = 0.045 and p = 0.015). CCT generally decreases over time and there are no differences in CCT at day 14 compared to the control, although CCT does not revert to levels observed in control rabbits. * Statistically significant by Student’s t-test</p