Organometallic halide perovskites CH 3 NH 3 PbX 3 (X = I, Br, Cl) have quickly become one of the most promising semiconductors for solar cells, with photovoltaics made of these materials reaching power conversion efficiencies of near 20%. Improving our ability to harness the full potential of organometal halide perovskites will require more controllable syntheses that permit a detailed understanding of their fundamental chemistry and photophysics. In this manuscript, we systematically synthesize CH 3 NH 3 PbX 3 (X = I, Br) nanocrystals with different morphologies (dots, rods, plates or sheets) by using different solvents and capping ligands. CH3NH3PbX3 nanowires and nanorods capped with octylammonium halides show relatively higher photoluminescence (PL) quantum yields and long PL lifetimes. CH3NH3PbI3 nanowires monitored at the single particle level show shape-correlated PL emission across whole particles, with little photobleaching observed and very few off periods. This work highlights the potential of low-dimensional organometal halide perovskite semiconductors in constructing new porous and nanostructured solar cell architectures, as well as in applying these materials to other fields such as light-emitting devices and single particle imaging and tracking.Keywords organometal halide perovskites, nanocrystals, preferred orientation, morphology control, size control, single particle photoluminescence Disciplines Chemistry CommentsReprinted (adapted) with permission from ACS Nano 9 (2015) 15,16 respectively, as well as high absorption coefficients. Critically, organolead perovskites have very long electronÀ hole carrier diffusion lengths, exceeding 1 μm in CH 3 NH 3 PbI 3-x Cl x , and 100 nm in CH 3 NH 3 PbI 3 , which in principle allows for the development of several solar cell architectures including perovskite-sensitized solar cells, planar heterojunction solar cells, and meso-and nanostructured solar cells. 17 Building on the dramatic improvement of solar cell performance using the solid hole conductor spiro-OMeTAD instead of a liquid electrolyte (spiro-OMeTAD stands for 2,2 0 -7,7 0 -tetrakis(N,N-di-p-methoxy-phenylamine)-9,9 0 -spirobifluorene), 18 the energy conversion efficiency of photovoltaics made from these intensely absorbing, visible-active semiconductors has risen from 3.8% to near 20% in only four years. 19,20 Photovoltaic performance depends critically on perovskite composition, crystallinity and morphology. 21À23 Higher perovskite film uniformity leads to lower recombination rates in planar heterojuction solar cells. 24,25 Film uniformity is affected by factors such as precursor composition, annealing temperature and, if applicable, solvent used during the vapor-assisted or spin coating deposition process. 6,24,26À32 Highly efficient mesostructured solar cells are produced by a twostep deposition process. 33À35 Vapor-assisted methods and additives provide the means * Address correspondence to jwp@iastate.edu, esmith1@iastate.edu, vela@iastate.edu.Received for review December 9, 2014 a...

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Experimental data for waveguide-coupled surface-plasmon-polariton (SPP) cones generated from dielectric waveguides is presented. The results demonstrate a simpler route to collect plasmon waveguide resonance (i.e., PWR) data. In the reverse-Kretschmann configuration (illumination from the sample side) and Kretschmann configuration (illumination from the prism side), all the waveguide modes are excited simultaneously with p-or s-polarized incident light, which permits rapid acquisition of PWR data without the need to scan the incident angle or wavelength, in the former configuration. The concentric SPP cone properties depend on the thickness and index of refraction of the waveguide. The angular intensity pattern of the cone is well-matched to simulation results in the reverse-Kretschmann configuration, and is found to be dependent on the polarization of the incident light and the polarization of the waveguide mode. In the Kretschmann geometry, all waveguide-coupled SPP cones are measured at incident angles that produce attenuated light reflectivity. In addition, the enhanced electric field produced under total internal reflection allows high signal-to-noise ratio multimodal spectroscopies (e.g., Raman scattering, luminescence) to measure the chemical content of the waveguide film, which traditionally is not measured with PWR. AbstractExperimental data for waveguide-coupled surface-plasmon-polariton (SPP) cones generated from dielectric waveguides is presented. The results demonstrate a simpler route to collect plasmon waveguide resonance (i.e., PWR) data. In the reverse-Kretschmann configuration (illumination from the sample side) and Kretschmann configuration (illumination from the prism side), all the waveguide modes are excited simultaneously with p-or s-polarized incident light, which permits rapid acquisition of PWR data without the need to scan the incident angle or wavelength. The concentric SPP cone properties depend on the thickness and index of refraction of the waveguide. The angular intensity pattern of the cone is well-matched to simulation results in the reverse-Kretschmann configuration, and is found to be dependent on the polarization of the incident light and the polarization of the waveguide mode. In the Kretschmann geometry, all waveguide-coupled SPP cones are measured at incident angles that produce attenuated light reflectivity. In addition, the enhanced electric field produced under total internal reflection allows high signal-to-noise ratio multimodal spectroscopies (e.g., Raman scattering, luminescence) to measure the chemical content of the waveguide film, which traditionally is not measured with PWR.