The carrier collection efficiency (ηc) and energy conversion efficiency (ηe) of polymer photovoltaic cells were improved by blending of the semiconducting polymer with C60 or its functionalized derivatives. Composite films of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) and fullerenes exhibit ηc of about 29 percent of electrons per photon and ηe of about 2.9 percent, efficiencies that are better by more than two orders of magnitude than those that have been achieved with devices made with pure MEH-PPV. The efficient charge separation results from photoinduced electron transfer from the MEH-PPV (as donor) to C60 (as acceptor); the high collection efficiency results from a bicontinuous network of internal donor-acceptor heterojunctions.

/pdf/polymer-photovoltaic-cells-enhanced-efficiencies-via-a-2lwj3yarfe.pdf

Polymer photovoltaic cells : enhanced efficiencies via a network of internal donor-acceptor heterojunctions

Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2

http://pubs.acs.org/doi/pdf/10.1021/cr1002326

Solar Water Splitting Cells

Evidence for photoinduced electron transfer from the excited state of a conducting polymer onto buckminsterfullerene, C(60), is reported. After photo-excitation of the conjugated polymer with light of energy greater than the pi-pi* gap, an electron transfer to the C(60) molecule is initiated. Photoinduced optical absorption studies demonstrate a different excitation spectrum for the composite as compared to the separate components, consistent with photo-excited charge transfer. A photoinduced electron spin resonance signal exhibits signatures of both the conducting polymer cation and the C(60) anion. Because the photoluminescence in the conducting polymer is quenched by interaction with C(60), the data imply that charge transfer from the excited state occurs on a picosecond time scale. The charge-separated state in composite films is metastable at low temperatures.

https://science.sciencemag.org/content/sci/258/5087/1474.full.pdf

Photoinduced electron transfer from a conducting polymer to buckminsterfullerene.

The interest in heterogeneous photocatalysis is intense and increasing, as shown by the number of publications on this theme which regularly appear in this journal, and the fact that over 2000 papers have been published on this topic since 1981. This article is an overview of the field of semiconductor photocatalysis : a brief examination of its roots, achievements and possible future. The semiconductor titanium dioxide (TiO 2 ) features predominantly in past and present work on semiconductor photocatalysis; as a result, in the most of the examples selected in this overview to illustrate various points the semiconductor is TiO 2 .

An overview of semiconductor photocatalysis

Preface Acknowledgements Notation Part I. Overview and Background Topics: 1. Introduction 2. Overview 3. Theoretical background 4. Periodic solids and electron bands 5. Uniform electron gas and simple metals Part II. Density Functional Theory: 6. Density functional theory: foundations 7. The Kohn-Sham ansatz 8. Functionals for exchange and correlation 9. Solving the Kohn-Sham equations Part III. Important Preliminaries on Atoms: 10. Electronic structure of atoms 11. Pseudopotentials Part IV. Determination of Electronic Structure, The Three Basic Methods: 12. Plane waves and grids: basics 13. Plane waves and grids: full calculations 14. Localized orbitals: tight binding 15. Localized orbitals: full calculations 16. Augmented functions: APW, KKR, MTO 17. Augmented functions: linear methods Part V. Predicting Properties of Matter from Electronic Structure - Recent Developments: 18. Quantum molecular dynamics (QMD) 19. Response functions: photons, magnons ... 20. Excitation spectra and optical properties 21. Wannier functions 22. Polarization, localization and Berry's phases 23. Locality and linear scaling O (N) methods 24. Where to find more Appendixes References Index.

Electronic Structure: Basic Theory and Practical Methods

A novel optical translator that can perform 3R-regeneration and wavelength conversion of high-speed return-to-zero signals is demonstrated at 20 Gbit/s. Efficient retiming and bit-error-rate performance is measured using a Mach-Zehnder interferometer with integrated semiconductor optical amplifiers.

20 Gbit/s all-optical regeneration and wavelength conversion using SOA based interferometers

Modification of the photoactive junction in semiconductor based photoelectrochemical cells to improve or stabilize the current–voltage characteristics under illumination has been attempted in many ways in the brief history of such energy converting devices. We discuss two such efforts with n-type gallium arsenide substrates. In one, polycrystalline films incorporating submonolayers of metal ions in the surface region show significant enhancement of power output in selenide–polyselenide cells. In the second, single crystals electroplated with noble metals and contacted by a redox solution to the resulting metal–semiconductor Schottky junction are examined for solar conversion prospects.

Surface modification in semiconductor liquid-junction cells

Etude experimentale de la passivation de surfaces et de joints de grains de p-InP par des submonocouches d'argent chimisorbe. Amelioration obtenue dans le rendement de cellules photoelectrochimiques utilisant ce materiau en photocathode

Chemical passivation of carrier recombination at acid interfaces and grain boundaries of p-indium phosphide

As optical access to the loop becomes more advanced, using emerging fiber to the loop (FTTL) architectures, and with the possible use of wavelength division multiplexing (WDM) to enhance transmission capacity and networking flexibility, it is important to consider new components that may be useful as building blocks for the upcoming local access networks. Obviously, for FTTL applications, low cost is an important prerequisite for components that are not widely shared. This may require uncooled operation, ease of packaging, and perhaps integration of opto-electronic devices. One of the new FTTL- WDM architectures that was recently demonstrated is RITE-Net [1,2], which is based on a WDM signals from a central office sent downstream to a remote node, and then to the local optical network unit (ONU). The carrier wavelength is modulated at the ONU using an on site optical modulator and returned upstream to the central office. One parameter that effects the performance is the insertion loss of the modulator. To improve the power budget of the system, it might be useful to employ a component that has integrated modulators and a semiconductor optical amplifier (SOA) resulting in a modest fiber to fiber gain rather than a large insertion loss. The proposed component can also enable WDM networks where frequency conversion and/or signal equalization over a large dynamic input range is required. It may be useful to integrate two modulators, so that one can be used for data encoding and the other for power level equalization.

A Polarization Insensitive Semiconductor Optical Amplifier with Integrated Electroabsorption Modulators

We propose and demonstrate a simple, potentially low-cost, photonic integrated circuit that can operate as a transceiver in a ping-pong optical data-link configuration. The device is designed for uncooled operation, with a gain section, a detector, and a beam expander inside a Fabry-Perot cavity. The detector has a 1.4 /spl mu/m quaternary layer with a broad spectral responsivity range extending to 33 nm higher than the lasing wavelength of the device. The transmitter can provide 8 dBm inside a single-mode fiber, and the beam expander relaxes the alignment tolerance to a single-mode fiber.

Barry Miller

Papers

20 Gbit/s all-optical regeneration and wavelength conversion using SOA based interferometers

Surface modification in semiconductor liquid-junction cells

Chemical passivation of carrier recombination at acid interfaces and grain boundaries of p-indium phosphide

A Polarization Insensitive Semiconductor Optical Amplifier with Integrated Electroabsorption Modulators

A bi-directional transceiver PIC for ping-pong local loop configurations operating at 1.3-μm wavelength