To bridge the gap between laboratory research and commercial applications, it is vital to develop scalable methods to produce large quantities of high-quality and solution-processable few-layer phosphorene (FLBP). Here, we report an ultrafast cathodic expansion (in minutes) of bulk black phosphorus in the nonaqueous electrolyte of tetraalkylammonium salts that allows for the high-yield (>80%) synthesis of nonoxidative few-layer BP flakes with high crystallinity in ambient conditions. Our detailed mechanistic studies reveal that cathodic intercalation and subsequent decomposition of solvated cations result in the ultrafast expansion of BP toward the high-yield production of FLBP. The FLBPs thus obtained show negligible structural deterioration, excellent electronic properties, great solution processability, and high air stability, which allows us to prepare stable BP inks (2 mg/mL) in low-boiling point solvents for large-area inkjet printing and fabrication of optoelectronic devices.

Strong field enhancement and confinement in plasmonic nanostructures provide suitable conditions for nonlinear optics in ultracompact dimensions. Despite these enhancements, second-harmonic generation (SHG) is still inefficient due to the centrosymmetric crystal structure of the bulk metals used, e.g., Au and Ag. Taking advantage of symmetry breaking at the metal surface, one could greatly enhance SHG by engineering these metal surfaces in regions where the strong electric fields are localized. Here, we combine top-down lithography and bottom-up self-assembly to lodge single rows of 8 nm diameter Au nanoparticles into trenches in a Au film. The resultant "double gap" structures increase the surface-to-volume ratio of Au colocated with the strong fields in ∼2 nm gaps to fully exploit the surface SHG of Au. Compared to a densely packed arrangement of AuNPs on a smooth Au film, the double gaps enhance SHG emission by 4200-fold to achieve an effective second-order susceptibility χ((2)) of 6.1 pm/V, making it comparable with typical nonlinear crystals. This patterning approach also allows for the scalable fabrication of smooth gold surfaces with sub-5 nm gaps and presents opportunities for optical frequency up-conversion in applications that require extreme miniaturization.

High-performance perovskite solar cells (PSCs) are obtained through optimization of the formation of CH3NH3PbI3 nanocrystals on mesoporous TiO2 film, using a two-step sequential deposition process by first spin-coating a PbI2 film and then submerging it into CH3NH3I solution for perovskite conversion (PbI2 + CH3NH3I → CH3NH3PbI3). It is found that the PbI2 morphology from different film formation process (thermal drying, solvent extraction, and as-deposited) has a profound effect on the CH3NH3PbI3 active layer formation and its nanocrystalline composition. The residual PbI2 in the active layer contributes to substantial photocurrent losses, thus resulting in low and inconsistent PSC performances. The PbI2 film dried by solvent extraction shows enhanced CH3NH3PbI3 conversion as the loosely packed disk-like PbI2 crystals allow better CH3NH3I penetration and reaction in comparison to the multicrystal aggregates that are commonly obtained in the thermally dried PbI2 film. The as-deposited PbI2 wet film, without any further drying, exhibits complete conversion to CH3NH3PbI3 in MAI solution. The resulting PSCs reveal high power conversion efficiency of 15.60% with a batch-to-batch consistency of 14.60 ± 0.55%, whereas a lower efficiency of 13.80% with a poorer consistency of 11.20 ± 3.10% are obtained from the PSCs using thermally dried PbI2 films.

Molybdenum oxide (MoO 3 ) is a promising anode buffer layer (ABL) for high-performance organic photovoltaic (OPV) devices. However, the reasons for the enhanced performances remain unclear. In this work, we show that defect states play an important, if not dominating, role in improving the OPV performances. The changes in both the density of defect states and the work function of MoO 3 with annealing are shown and correlated with the OPV device performance. The increased defect densities improve the OPV performance through an enhanced hole extraction rate at the MoO 3 / organic interface. The reduction in work function, however, reduces the interface field that can possibly lower mobility near the interface and reduce the electron-blocking effect. This plays a role in saturation of the device performance. This work, therefore, shows the importance of the defects in MoO 3 as an ABL and a dominance of defect-enhanced extraction over a field-enhanced extraction process.

Compact electrical sources of surface plasmon polaritons (SPPs) are promising for integration with highspeed electronics. Being a highly compact source, the point dipole has the ability to directly couple to surface plasmon modes, and be electrically driven through the inelastic tunneling of electrons, for example, at the tip of a scanning tunneling microscope (STM). However, the directional control of electrically excited SPPs from such compact sources has not been demonstrated, despite its importance in controlling the optical energy flow on a chip. In this paper, we present a comprehensive analysis of the directional excitation of SPPs on Au 1D cavity by moving an STM tip relative to the edge of the cavity stripe and analyzing the light collected through an inverted microscope. The directional propagation of the SPP and its far-field emission exhibit a clear cyclic dependence on the relative distance from this edge. These results provide key steps toward realizing compact solid-state devices with the ability to excite and direct the propagation of light.

The effect of oxygen induced traps on charge mobility in bulk heterojunction solar cells using poly (3-hexylthiophene) (P3HT):1-(3-methoxycarbonyl)-propyl-1phenyl-(6, 6) methanofullerene (PCBM) blend have been studied using photoinduced charge extraction by linearly increasing voltage (PhotoCELIV) technique. The solar cells exposed to oxygen exhibit dual PhotoCELIV peaks, whereas the solar cell without oxygen treatment show single PhotoCELIV peak with the charge mobility of the order of 10-4 cm 2 /Vs. It is demonstrated that the oxygen treatment imbalance the charge mobility in the P3HT/PCBM photoactive layer, which affects the power conversion efficiency and lifetime of the solar cell. The single PhotoCELIV peak for the device without oxygen treatment indicates that the charge mobility is balanced, that causes the overlapping of electron and hole transients.

In this series, 10% of the abnormal cholangiograms occurred in patients without preoperative risk factors for bile duct stones. Altogether, 88 IOCs (31%) were cleared after either simple flushing or trawling with a Dormia basket. Formal LBDE was not required for 40% of abnormal cholangiograms. Simple transcystic manipulations to clear the bile ducts justify the use of routine IOC in units without laparoscopic biliary expertise.

The photoluminescence quantum yield (PLQY) of copper indium sulfide (CIS) quantum dots (QDs) improves significantly after a shelling procedure as the shell materials, like zinc sulfide, mitigate surface defects and reduce nonradiative recombinations. However, it is widely observed that the PLQY reduces when QDs are cast as a solid film from their solution, and PL peak emission also red-shifts, which suggests a relaxation of the quantum confinement effect. This could be due to thin zinc sulfide shells. Unlike cadmiumbased QDs, reports on a thick zinc chalcogenide shell on CIS QDs are limited. Efforts to grow larger shells have been stymied by zinc diffusion toward the core, causing cation exchange and alloy formation. Thick zinc chalcogenide shell growth typically requires higher temperatures, a regime which would irreversibly degrade the PL of a CIS QD. Here, we develop a technique to grow thicker shells on CIS QDs to improve the quantum confinement effect between the QDs. With these thick shell CIS QDs, we demonstrate better emission as well as thermal and chemical stability. Finally, we demonstrate their application in a luminescent solar concentrator and showed that it has better light harvesting characteristics than its thin shell counterpart.