Quantum-cutting Yb3+:CsPb(Cl1−xBrx)3 nanocrystals mitigate thermalization and reabsorption losses in a new monolithic bilayer luminescent solar concentrator device architecture.

Carrier spins in semiconductor nanocrystals are promising candidates for quantum information processing. Using a combination of time-resolved Faraday rotation and photoluminescence spectroscopies, we demonstrate optical spin polarization and coherent spin precession in colloidal CsPbBr 3 nanocrystals that persists up to room temperature. By suppressing the influence of inhomogeneous hyperfine fields with a small applied magnetic field, we demonstrate inhomogeneous hole transverse spin-dephasing times (! ! *) that approach the nanocrystal photoluminescence lifetime, such that nearly all emitted photons derive from coherent hole spins. Thermally activated LO phonons drive additional spin dephasing at elevated temperatures, but coherent spin precession is still observed at room temperature. These data reveal several major distinctions between spins in nanocrystalline and bulk CsPbBr 3 and open the door for using metal-halide perovskite nanocrystals in spin-based quantum technologies.

Inorganic lead halide perovskite nanocrystals (NCs) are an exciting class of luminescent materials with high defect tolerance and broad spectral tunability, but such NCs are vulnerable to degradation under ambient conditions. Here, we report a class of modular zwitterion-functionalized isopropyl methacrylate polymers designed to stabilize a wide variety of perovskite NCs of different compositions, while also enabling processing in green solvents. Specifically, we report polymers in which the zwitterion spacing is tuned to accommodate the different lattice parameters of CsPb(Cl 1−x Br x ) 3 and CsPbI 3 NCs, and we report partially fluorinated polymers prepared to accommodate the needs of infrared-emitting NCs. We show that as-synthesized CsPbBr 3 , CsPbI 3 , and Yb 3+ :CsPbCl 3 NCs are easily transferred into these zwitterionic polymers via a simple ligand-exchange procedure. These NC/polymer composites were then cast into thin films that showed substantially improved photoluminescence (PL) and stability compared with more conventional NC/polymer films. Specifically, CsPbBr 3 and CsPbI 3 NCs in films of their appropriately designed polymers had PL quantum yields of ∼90% and ∼80%, respectively. PL quantum yields decreased under continuous illumination but self-healed completely after dark storage. We also found that all the NC compositions studied here maintain their PL quantum yields in NC/polymer composite films even after 1 year of ambient storage. These encouraging results demonstrate the utility of such modular zwitterion-functionalized polymers for hosting specific perovskite NCs, potentially opening avenues for robust new photonic applications of this important class of NCs.

Overcoming the challenges of patterning luminescent materials will unlock additive and more sustainable paths for the manufacturing of next-generation on-chip photonic devices. Electrohydrodynamic (EHD) inkjet printing is a promising method for deterministically placing emitters on these photonic devices. However, the use of this technique to pattern luminescent lead halide perovskite nanocrystals (NCs), notable for their defect tolerance and impressive optical and spin coherence properties, for integration with optoelectronic devices remains unexplored. In this work, we additively deposit nanoscale CsPbBr3 NC features on photonic structures via EHD inkjet printing. We perform transmission electron microscopy of EHD inkjet printed NCs to demonstrate that the NCs’ structural integrity is maintained throughout the printing process. Finally, NCs are deposited with sub-micrometer control on an array of parallel silicon nitride nanophotonic cavities and demonstrate cavity–emitter coupling via photoluminescence spectroscopy. These results demonstrate EHD inkjet printing as a scalable, precise method to pattern luminescent nanomaterials for photonic applications.

Inorganic–organic interfaces: a tutorial on using organic functional groups to enhance the performances and/or enable new functionality of inorganic nanomaterials.

Organic hybrid light-emitting diodes (hybrid-LEDs) employ organic dyes as light converters on top of commercial blue inorganic LEDs, replacing incumbent inorganic phosphor light converters synthesized from rare-earth and/or toxic metallic...

Light-emitting diodes (LEDs) are a lighting technology with a huge and ascending market. Typically, LED backlights are often paired with inorganic phosphors made from rare-earth elements (REEs) to tune the emission lineshapes for different applications. However, REE production is a resource-intensive process with many negative environmental impacts. Herein we develop organic hybrid LEDs using organic dyes synthesized from an abundant and non-toxic natural product (theobromine) to replace REE phosphors. The resulting hybrid LED generates continuous emission from 400 -740 nm, resulting in high color rendering index (the current industry standard) of 90 and color fidelity index (the most advanced and comprehensive standard) of 92, challenging commercial LEDs based on REE phosphors. In addition, the light-converting composite is made from 99 wt% SBS, an inexpensive industrial polymer, and 1wt% theobromine dyes, reducing the cost of the light converter to ¢1.30 for a 1 W LED, compared to approximately ¢ 19.2 of commercial products. The light converting efficiency of the dye-SBS composite is 82%. Excited state kinetics experiments were also conducted to provide guidance to further increase the light-converting efficiency of the theobromine dyes while maintaining excellent color rendering and fidelity. File list (2) download file view on ChemRxiv Supporting Information.pdf (610.92 KiB) download file view on ChemRxiv Theobromine and CRI CFI.pdf (1.00 MiB)

Titanium dioxide nanoparticles with disordered outermost layer sturctures have significantly enhanced light absorption and photocatalytic properties and thus receiving enhanced attention in recent years. Engineering the outermost layers using in situ magnesium doping to tailor the band‐edge of TiO2 nanoparticles was achieved via a flame aerosol reactor. The distribution of doped elements in nanoparticles could be controlled in a high temperature flame process, and which could be predicted by the comparison of different characteristic time scales, such as reaction time, coagulation time, and sintering time is proposed. In situ magnesium doping on the outermost layers effectively tailored the conduction band and electron structure of the TiO2 nanoparticles, and simultaneously improved the maximum photocurrent as well as the maximum photovoltage in dye‐sensitized solar cells. These improvements were largely attributed to red‐shifted light absorption, and rapid photoelectron injection into the conduction band. © 2016 American Institute of Chemical Engineers AIChE J, 63: 870–880, 2017