Optics and photonics articles within Nature Materials

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  • Letter |

    A highly selective and efficient approach to covalently bond complementary DNA strands in solution and on surfaces on demand is shown. The approach involves the substitution of a pair of complementary bases by cinnamate-based crosslinks, which can be activated on exposure to ultraviolet light, and allows chemical patterning of flat and curved surfaces down to micrometre and potentially submicrometre resolutions.

    • Lang Feng
    • , Joy Romulus
    •  & Paul Chaikin

  • Article |

    Photoelectrochemical water-splitting is a promising route for the renewable production of hydrogen, but trade-offs between photoelectrode stability and efficiency remain problematic. A metal–oxide–semiconductor photoelectrode architecture demonstrates stable and efficient water splitting using narrow-bandgap semiconductors. Substantial improvement in the performance of Si-based photocathodes is achieved by combining a high-quality SiO2 layer and bilayer metal catalysts.

    • Daniel V. Esposito
    • , Igor Levin
    •  & A. Alec Talin

  • Article |

    Josephson plasma solitons are a kind of excitation predicted to occur in cuprate superconductors subject to strong electromagnetic fields. By using intense radiation from a free-electron laser, these modes are now demonstrated experimentally in the copper oxide material La1.84Sr0.16CuO4.

    • A. Dienst
    • , E. Casandruc
    •  & A. Cavalleri

  • Commentary |

    Unique opportunities arise from exceptional points that coalesce states of an open system in synthetic photonic media, where delicately balanced complex dielectric functions produce unprecedented optical properties.

    • Xiaobo Yin
    •  & Xiang Zhang

  • News & Views |

    Excitation of organic donor–acceptor systems with high-energy light can produce hot charge-transfer states that are delocalized across the heterojunction and readily dissociate. Two studies now reveal the dynamics of this process and pave the way towards unravelling the details of the molecular landscape that favours fast photocarrier generation.

    • Carlos Silva

  • Article |

    Non-trivial topological phases can allow for one-way spin-polarized transport along the interfaces of topological insulators but they are relatively uncommon in the condensed state of matter. By arranging judiciously designed metamaterials into two-dimensional superlattices, a photonic topological insulator has now been demonstrated theoretically, enabling unidirectional spin-polarized photon propagation without the application of external magnetic fields or breaking of time-reversal symmetry.

    • Alexander B. Khanikaev
    • , S. Hossein Mousavi
    •  & Gennady Shvets

  • Letter |

    The standard picture of organic photovoltaics predicts that excitons, which are created under light irradiation, thermalize before dissociation into free electrons and holes. Experimental results and calculations on a low-bandgap polymer–fullerene blend now illustrate the dynamics of hot charge-transfer states and their contribution to charge generation in bulk heterojunctions.

    • G. Grancini
    • , M. Maiuri
    •  & G. Lanzani

  • Article |

    Photocurrent generation in organic solar cells relies on the dissociation of excitons into free electrons and holes at donor/acceptor heterointerfaces. Femtosecond spectroscopy and non-adiabatic simulations on the phthalocyanine–fullerene model system now reveal the relaxation dynamics of hot charge-transfer excitons in this process.

    • Askat E. Jailaubekov
    • , Adam P. Willard
    •  & X-Y. Zhu

  • Letter |

    The appealing electronic properties of the monolayer semiconductor molybdenum disulphide make it a candidate material for electronic devices. The observation of tightly bound trions in this system—which have no analogue in conventional semiconductors—opens up possibilities for controlling these quasiparticles in future optoelectronic applications.

    • Kin Fai Mak
    • , Keliang He
    •  & Jie Shan

  • Letter |

    Metamaterials offer a unique potential to guide the propagation of light. However, existing designs of devices such as invisibility cloaks require a restrictive range of materials parameters for their realization. A new approach to cloak devices now lifts such restrictions allowing for a greater flexibility in device design.

    • Nathan Landy
    •  & David R. Smith

  • Article |

    Photoconversion in organic photovoltaic cells, which relies on charge generation at donor/acceptor interfaces, is limited by short exciton-diffusion-lengths. Diluting an electron donor into a wide-energy-gap host material has now led to an ~50% increase in exciton diffusion length and enhanced power conversion efficiencies in planar heterojunction cells compared with optimized devices with an undiluted donor layer.

    • S. Matthew Menke
    • , Wade A. Luhman
    •  & Russell J. Holmes

  • Review Article |

    Metamaterials are man-made structures that allow optical properties to be shaped on length scales far smaller than the wavelength of light. Although metamaterials were initially considered mainly for static applications, this Review summarizes efforts towards an active functionality that enables a much broader range of photonic device applications.

    • Nikolay I. Zheludev
    •  & Yuri S. Kivshar

  • Letter |

    Optical coatings usually consist of many multilayers of thin films to achieve the desired properties. A new approach using interference effects between an absorbing dielectric film and a metallic substrate now enables ultrathin optical coatings that could also find applications as thin solar cells or photodetectors.

    • Mikhail A. Kats
    • , Romain Blanchard
    •  & Federico Capasso

  • Letter |

    Liquid-crystalline order can be templated in a material by refilling a photopolymerized liquid-crystal cast with the material after the non-polymerized portion has been washed out. This approach has now been used to template, in achiral liquid crystals, chiral three-dimensional blue phases with unprecedented thermal stability that are suitable for narrowband mirrorless lasing and switchable electro-optic devices.

    • F. Castles
    • , F. V. Day
    •  & H. J. Coles

  • Editorial |

    Progress in photovoltaic technology could soon mean grid parity for solar electricity. In this issue we highlight scientific as well as science-policy strategies aimed towards achieving this goal.

  • Commentary |

    For decades, solar-cell efficiencies have remained below the thermodynamic limits. However, new approaches to light management that systematically minimize thermodynamic losses will enable ultrahigh efficiencies previously considered impossible.

    • Albert Polman
    •  & Harry A. Atwater

  • News & Views |

    The application of inhomogeneous strain to silicon photonic structures may lead to new optically active devices based on second-order nonlinear processes.

    • Clemens Schriever
    •  & Ralf B. Wehrspohn

  • Letter |

    Vesicles can rupture as a result of an imbalance in osmotic pressure between their inside and the exterior. Such an ‘osmotic shock’ has now been multiplexed in a coordinated fashion within an ordered material in which a minor component swells and ruptures, thus leading to a porous bicontinuous structure. Such perforated ordered materials may find applications in photonics, optoelectronics and nanofiltration.

    • Paul Zavala-Rivera
    • , Kevin Channon
    •  & Hernan Miguez

  • Article |

    Plasmonic nanostructures are known to be an attractive platform for highly sensitive molecular sensors, although they often lack specificity. A plasmonic device with a sharp optical resonance tuned to biomolecules selectively captured on the surface of the device now offers a versatile yet highly specific platform for molecular sensing.

    • Chihhui Wu
    • , Alexander B. Khanikaev
    •  & Gennady Shvets

  • Letter |

    Polymer-based bulk-heterojunction solar cells have shown some of the highest photoconversion efficiencies in organic photovoltaics, but polymer polydispersity impacts their performance. A small-molecule donor is now reported that enables the fabrication of bulk-heterojunction devices with low acceptor content and photoconversion efficiencies of up to 6.7%.

    • Yanming Sun
    • , Gregory C. Welch
    •  & Alan J. Heeger

  • Article |

    Nonlinear optical upconversion processes in nanoparticles, which convert long-wavelength light into short-wavelength emission, are promising for applications such as biological imaging, optical data storage and others. The flexible tuning of upconversion properties in core–shell nanoparticles now offers unprecedented control over the nonlinear optical properties of the nanoparticles.

    • Feng Wang
    • , Renren Deng
    •  & Xiaogang Liu

  • Letter |

    Conjugated polymers are applied widely in organic optoelectronic devices. The performance of these devices depends critically on polymer morphology, which can be modified by solvent vapour annealing. This process has now been controlled on mesoscopic length scales, bridging the gap between single-molecule and bulk studies, and revealing long-range energy transport in ordered polymer aggregates.

    • Jan Vogelsang
    • , Takuji Adachi
    •  & Paul F. Barbara

  • Article |

    Inorganic nanocrystals are attractive materials for solar-cell applications. However, their performance is often limited by an insufficient alignment of internal energy levels. A tuning of these energy levels has now been achieved by attaching two different molecules to a single nanocrystal, which significantly alters its electronic and optoelectronic properties.

    • Nir Yaacobi-Gross
    • , Michal Soreni-Harari
    •  & Nir Tessler

  • News & Views |

    X-ray illumination can be used to control the arrangement of oxygen atoms in cuprate superconductors, allowing the writing of regions of robust high-transition-temperature superconductivity.

    • Peter Littlewood

  • Article |

    Organic ligands enhance the stability and the solution processability of semiconductor quantum dots, but they can impede charge transport in films of such nanoparticles. Passivation with atomic ligands now offers an alternative strategy that enables the fabrication of PbS colloidal-quantum-dot solar cells with power-conversion efficiencies of up to 6%.

    • Jiang Tang
    • , Kyle W. Kemp
    •  & Edward H. Sargent

  • Letter |

    Three-dimensional photonic devices are of interest as light emitters, detectors or waveguides. However, so far their fabrication has remained a challenge. The template-directed epitaxy of three-dimensional semiconductor structures now offers a new strategy for the realization of photonic devices, demonstrated by the realization of a three-dimensional photonic crystal light-emitting diode.

    • Erik C. Nelson
    • , Neville L. Dias
    •  & Paul V. Braun

  • Article |

    The energy-level alignment at the heterojunction critically influences the performance of organic photovoltaic devices. It is now shown that the surface dipole moments of individual organic semiconductor films can be tuned with surface-segregated monolayers before forming bilayer solar cells by a simple film-transfer method.

    • Akira Tada
    • , Yanfang Geng
    •  & Keisuke Tajima

  • News & Views |

    A study of nitrogen doping of graphene reveals the potential of high-resolution electron microscopy for imaging charge transfer around chemical bonds.

    • Knut W. Urban

  • News & Views |

    The friction and wear of materials is part of our everyday experience, and yet these processes are not well understood. The example of diamond highlights wear processes that result from bumping atoms, showing that the devil is indeed in the details.

    • Jay Fineberg

  • Letter |

    The only way diamond can be polished is by pressing it against small diamond crystals, but this works well only for certain crystallographic orientations. The details of this wear mechanism have now been uncovered in simulations that suggest wear occurs via a thin amorphous layer on the diamond surface.

    • Lars Pastewka
    • , Stefan Moser
    •  & Michael Moseler

  • News & Views |

    Biocompatible light-emitting structures based on high-performance inorganic compound semiconductors on flexible substrates open the path to futuristic therapeutic devices, instrumented surgical gloves and many other applications.

    • Takao Someya

  • Article |

    Flexible electronic devices that can be stretched without losing performance have seen increasing functionality. In particular, the demonstration of light-emitting diodes and photodetectors on flexible electronic substrates now opens the door to applications of flexible optoelectronic sheets in biomedicine and robotics.

    • Rak-Hwan Kim
    • , Dae-Hyeong Kim
    •  & John A. Rogers

  • Article |

    Excitons in polycrystalline films of organic semiconductors typically migrate distances of the order of tens of nanometres. Photoconductivity measurements in highly ordered rubrene now show that exciton diffusion can reach the micrometre range, opening a route to designing excitonic circuitry for applications in photocatalysis, photochemical sensing or photovoltaic energy conversion.

    • H. Najafov
    • , B. Lee
    •  & V. Podzorov

  • Letter |

    Terahertz emitters, such as quantum cascade lasers (QCLs), are of interest for applications in imaging and sensing. Nevertheless, performance problems such as power out-coupling efficiency have limited their technological potential. However, a study now shows that subwavelength surface patterning of terahertz QCLs leads to significantly enhanced beam collimation and power collection efficiency.

    • Nanfang Yu
    • , Qi Jie Wang
    •  & Federico Capasso

  • Letter |

    Fibres are typically used as passive devices, whether in fibre-optical cables used in telecommunciations or as yarns for clothing. The demonstration of polymer-based piezoelectric fibres that can be drawn to tens of metres in length, and whose acoustic response can be actively controlled, suggests possible applications in, for example, medical imaging or acoustic sensing.

    • S. Egusa
    • , Z. Wang
    •  & Y. Fink

  • Review Article |

    Transformation optics describes the capability to design the path of light waves almost at will through the use of metamaterials that control effective materials properties on a subwavelength scale. In this review, the physics and applications of transformation optics are discussed.

    • Huanyang Chen
    • , C. T. Chan
    •  & Ping Sheng

  • News & Views |

    A solar-cell design based on silicon microwires achieves efficient absorption of sunlight while using only 1% of the active material used in conventional designs.

    • Jia Zhu
    •  & Yi Cui

  • Letter |

    The use of silicon nanostructures in solar cells offers a number of benefits, such as the fact they can be used on flexible substrates. A silicon wire-array structure, containing reflecting nanoparticles for enhanced absorption, is now shown to achieve 96% peak absorption efficiency, capturing 85% of light with only 1% of the silicon used in comparable commercial cells.

    • Michael D. Kelzenberg
    • , Shannon W. Boettcher
    •  & Harry A. Atwater

  • News & Views |

    The realization of electrical sources of surface plasmon polaritons using complementary metal oxide semiconductor technology is a significant step towards silicon-compatible nanoscale photonic devices.

    • Aaron Hryciw
    • , Young Chul Jun
    •  & Mark L. Brongersma

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