Hybrid nanoplasmonics is a recent and promising branch of research, that attempts to control the energy transfer between nano-emitters and surface plasmons. Colloidal quantum dots are good emitters due to their unique set of optical properties. In our work, quantum dots were excited in close proximity to a silver nanowire and the quantum dot emission was transferred into guided propagating nanowire surface plasmons (SPs) that were scattered at the nanowire end. Compared with metallic nanoparticles, silver nanowires enable the propagation of SPs in a well-defined direction along the nanowire axis, allowing for long-distance energy transfer between the nano-emitter and a specific nanowire point of interest. The challenge related to this promising hybrid system is to control the position of quantum dots on the nanowire. Our approach of nano-emitters positioning is based on two-photon photopolymerization of a photosensitive material containing quantum dots. This approach allows one to use light for positioning the quantum dots on the plasmonic nanosystem in a controlled manner. We report on a new controlled hybrid plasmonic nanoemitter based on coupling between quantum dots and propagating surface plasmons that are supported by silver nanowires, considered as surface plasmons resonators and observed through their scattering at the nanowire ends. A parametric study of the distance between the quantum dots and the nanowire extremity shows that precise control of the position of the launching sites enables control of light intensity at the wire end, through surface plasmon propagation length. This new approach is promising to produce efficient acceptor-donor hybrid nano-systems.
Here we present two techniques, which have advantages in the perovskite single crystal devices. First, we demonstrate modulation-doped layer growth and double heterostructure using a millimeter-sized hybrid halide perovskite crystal as a substrate. We show that previously known limiting factor of halide ion inter-diffusion can be constrained to few microns by (1) using low halide composition gradient and (2) adjusting solution concentrations just above the critical super saturation. In the solvo-thermal growth process, our layer growth time could be conveniently extended as necessary to grow a uniform layer, with only ~5 µm inter-diffusion region. This is a significant improvement compared to few seconds dipping time previously reported for a rapid ion exchange process without any layer growth. The growth of CH3NH3PbBr3 layer on top of CH3NH3Pb(Br0.85Cl0.15)3 bulk substrate is studied for different growth times to obtain up to 30µm layer thickness. Ion diffusion profile, layer thickness and crystallographic orientation have been characterized by cross sectional characterization using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Electron Back-Scattering Diffraction (EBSD) . With this advancement, we are able to grow two consecutive perovskite layers to create a double heterostructure for the first time. Second, we demonstrate an as-grown milliliter-sized perovskite bulk crystal light emitting device. This device can be easily lighten up at low voltage (6-20 V) and at slightly low temperatures than room temperature (160-230 K). We are aiming to integrate both technologies with further optimization to produce efficient, pure-color perovskite light emitting devices for entire visible spectrum with low-cost and simple infrastructure.
Systematic investigation of temperature-dependence on thermal quenching of X-ray luminescence (XL) from various single perovskite crystals was carried out. In the family of methylammonium lead halide perovskites (MAPbX3, MA = methylammonium, X= Cl, Br or I), the quenching temperature of XL decreases from Cl to I. According to our analysis, such behavior is strongly affected by their corresponding decrease of thermal activation energy ▵Eq from 53 ± 3 to 6 ± 1 meV. Different concentrations of Bi3+-doped MAPbBr3 are also prepared and both four-point probe measurement and X-ray thermoluminescence (TL) confirms the successful doping. When we dope MAPbBr3 with Bi3+, Γ0/Γv increases to 78 ± 18 for crystal with Bi/Pb ratio of 1/10 in precursor solution.