Single Photon Emission from Single Perovskite Nanocrystals of Cesium Lead Bromide

The power conversion efficiency of photovoltaic devices based on semiconductor perovskites has reached ~20% after just several years of research efforts. With concomitant discoveries of other promising applications in lasers, light-emitting diodes and photodetectors, it is natural to anticipate what further excitements these exotic perovskites could bring about. Here we report on the observation of single photon emission from single CsPbBr3 perovskite nanocrystals (NCs) synthesized from a facile colloidal approach. Compared with traditional metal-chalcogenide NCs, these CsPbBr3 NCs exhibit nearly two orders of magnitude increase in their absorption cross sections at similar emission colors. Moreover, the radiative lifetime of CsPbBr3 NCs is greatly shortened at both room and cryogenic temperatures to favor an extremely fast output of single photons. The above findings have not only added a novel member to the perovskite family for the integration into current optoelectronic architectures, but also paved the way towards quantum-light applications of single perovskite NCs in various quantum information processing schemes

Plasmonic Multi‐Layered Built‐in Hotspots Nanogaps for Effectively Activating Analytes

Abstract Multi‐layered plasmonic nanostructures are able to highly promote the near‐field confinement and effectively activate analytes, which are of predominate significance but are extremely challenging. Herein, the semi‐open Au core@carved AuAg multi‐shell superstructure nanoparticles (multi‐Au@Ag‐Au NPs, multi = mono, bi, tri, tetra, and penta) are reported with a high designability on electromagnetic field and capability of effectively capturing analytes. By controlling synthetic parameters such as the number of galvanic exchange and Ag growth, multi‐Au@Ag‐Au NPs are successfully obtained, with tunable layer numbers and asymmetric nanoholes. Due to collective plasmon oscillations of multi‐layered built‐in nanogaps, the electromagnetic field strength of a single penta‐Au@Ag‐Au entity reach 48841. More importantly, the penta‐Au@Ag‐Au NPs show a remarkable light‐harvesting capability, which is adaptive to different Raman lasers, supporting high‐diversity detection. Additionally, the structural specificity allows analytes to be sufficiently captured into interior hotspots, and further achieve highly sensitive detection with limit of detection down to 3.22 × 10−12 M. This study not only provides an effective pathway for integrating abundant hotspots and activating target molecules in single plasmonic superstructure, but stimulates advancements in SERS substrates for various applications

Facile Face-Down Annealing Triggered Remarkable Texture Development in CH₃NH₃PbI₃ Films for High-Performance Perovskite Solar Cells

Herein, we demonstrate that the facile face-down annealing route which effectively confines the evaporation of residual solvent molecules in one-step deposited precursor films can controllably enable the formation of (110) textured CH₃NH₃PbI₃ films consisting of high-crystallinity well-ordered micrometer-sized grains that span vertically the entire film thickness. Such microstructural features dramatically decrease nonradiative recombination sites as well as greatly improve the transport property of charge carries in the films compared with that of the nontextured ones obtained by the conventional annealing route. As a consequence, the planar-heterojunction perovskite solar cells with these textured CH₃NH₃PbI₃ films exhibit significantly enhanced power conversion efficiency (PCE) along with small hysteresis and excellent stability. The champion cell yields impressive PCE boosting to 18.64% and a stabilized value of around 17.22%. Particularly, it can maintain 86% of its initial value after storage for 20 days in ambient conditions with relative humidity of 10–20%. Our work suggests a facile and effective route for further boosting the efficiency and stability of low-cost perovskite solar cells

Series of ZnSn(OH)₆ Polyhedra: Enhanced CO₂ Dissociation Activation and Crystal Facet-Based Homojunction Boosting Solar Fuel Synthesis

A series of ZnSn­(OH)₆ polyhedra are successfully explored with well-controlled area ratio of the exposed {100} and {111} facets. Band alignment of the exposed facet-based homojunction of the elegant polyhedron facilitates spatial separation of photogenerated electrons and holes on {111} and {100} surfaces, respectively. Optimal area ratio of {100} to {111} is the prerequisite for pronounced CO₂ photocatalytic performance of high-symmetry cuboctahedra into methane (CH₄). The synergistic effect of the excess electron accumulation and simultaneously the enhanced CO₂ absorption and low dissociation activation energy on {111} reduction sites promote the yield of CO₂ photocatalytic conversion product

Single-Mode Lasing from “Giant” CdSe/CdS Core–Shell Quantum Dots in Distributed Feedback Structures

“Giant” semiconductor quantum dots (GQDs) have tremendous potential for applications in laser devices. Here, CdSe/CdS core–shell GQDs (11 monolayers) have been synthesized as lasing gain material. The photoluminescence decay of the GQD ensemble is single-exponential, and the two-photon absorption cross-section is above 10⁵ GM. This article presents a versatile method for fabrication of CdSe/CdS GQD distributed feedback (DFB) lasers by laser interference ablation. A high-quality surface-relief grating structure can be readily created on the GQD thin films, and the relationship between laser beam intensity and surface modulation depth is studied. With appropriate periods, single-mode lasing emission has been detected from these devices under excitation wavelengths of 400 and 800 nm. The laser thresholds are as low as 0.028 and 1.03 mJ cm^–2, with the lasing <i>Q</i>-factors of 709 and 586, respectively. Lasing operation is realized from the direct laser interference-ablated QD DFB structures for the first time