A Photonic Crystal Laser from Solution Based Organo-Lead Iodide Perovskite Thin Films

Perovskite semiconductors are actively investigated for high performance solar cells. Their large optical absorption coefficient and facile solution-based, low-temperature synthesis of thin films make perovskites also a candidate for light-emitting devices across the visible and near-infrared. Specific to their potential as optical gain medium for lasers, early work has demonstrated amplified spontaneous emission and lasing at attractively low thresholds of photoexcitation. Here, we take an important step toward practically usable perovskite lasers where a solution-processed thin film is embedded within a two-dimensional photonic crystal resonator. We demonstrate high degree of temporally and spatially coherent lasing whereby well-defined directional emission is achieved near 788 nm wavelength at optical pumping energy density threshold of 68.5 ± 3.0 μJ/cm². The measured power conversion efficiency and differential quantum efficiency of the perovskite photonic crystal laser are 13.8 ± 0.8% and 35.8 ± 5.4%, respectively. Importantly, our approach enables scalability of the thin film lasers to a two-dimensional multielement pixelated array of microlasers which we demonstrate as a proof-of-concept for possible projection display applications

Cooperative Enhancement of Second-Harmonic Generation from a Single CdS Nanobelt-Hybrid Plasmonic Structure

Semiconductor nanostructures (<i>e</i>.<i>g</i>., nanowires and nanobelts) hold great promise as subwavelength coherent light sources, nonlinear optical frequency converters, and all-optical signal processors for optoelectronic applications. However, at such small scales, optical second-harmonic generation (SHG) is generally inefficient. Herein, we report on a straightforward strategy using a thin Au layer to enhance the SHG from a single CdS nanobelt by 3 orders of magnitude. Through detailed experimental and theoretical analysis, we validate that the augmented SHG originates from the mutual intensification of the local fields induced by the plasmonic nanocavity and by the reflections within the CdS Fabry–Pérot resonant cavity in this hybrid semiconductor–metal system. Polarization-dependent SHG measurements can be employed to determine and distinguish the contributions of SH signals from the CdS nanobelt and gold film, respectively. When the thickness of gold film becomes comparable to the skin depth, SHG from the gold film can be clearly observed. Our work demonstrates a facile approach for tuning the nonlinear optical properties of mesoscopic, nanostructured, and layered semiconductor materials

SnS₄^4–, SbS₄^3–, and AsS₃^3– Metal Chalcogenide Surface Ligands: Couplings to Quantum Dots, Electron Transfers, and All-Inorganic Multilayered Quantum Dot Sensitized Solar Cells

Three inorganic capping ligands (ICLs) for quantum dots (QDs), SnS₄^4–, SbS₄^3– and AsS₃^3–, were synthesized and the energy levels determined. Proximity between the ICL LUMO and QD conduction level governed the electronic couplings such as absorption shift upon ligand exchange, and electron transfer rate to TiO₂. QD-sensitized solar cells were fabricated, using the ICL-QDs and also using QD multilayers layer-by-layer assembled by bridging coordinations, and studied as a function of the ICL ligand and the number of QD layers

Morphology-Independent Stable White-Light Emission from Self-Assembled Two-Dimensional Perovskites Driven by Strong Exciton–Phonon Coupling to the Organic Framework

Hybrid two-dimensional (2D) lead halide perovskites have been employed in optoelectronic applications, including white-light emission for light-emitting diodes (LEDs). However, until now, there have been limited reports about white-light-emitting lead halide perovskites with experimental insights into the mechanism of the broadband emission. Here, we present white-light emission from a 2D hybrid lead chloride perovskite, using the widely known phenethylammonium cation. The single-crystal X-ray structural data, time-resolved photophysical measurements, and density functional theory calculations are consistent with broadband emission arising from strong exciton–phonon coupling with the organic lattice, which is independent of surface defects. The phenethylammonium lead chloride material exhibits a remarkably high color rendering index of 84, a CIE coordinate of (0.37,0.42), a CCT of 4426, and photostability, making it ideal for natural white LED applications