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 semiconductor optical 9mplifier array with 4 channels is presented. This SOA array was coupled to uncoated, flat end, single mode fibers using integrated adiabatic beam expanders, optical index matching gel, and specifically tailored TiO2 anti-reflection coatings. The TiO2 AR coating overcomes the indices misinatching of fiber glass and InP based device, and reduce optical reflection to 0.002% at 1.55 μm. The average coupling loss is 4.3 dB per facet for the devices measured. Fiber coupled small signal gain for the amplifiers is typically 11.6 dB and a saturation output power of 3.0 dBm. The method of characterization and optimization of the TiO2 coating is discussed.

Semiconductor Optical Amplifier Array with Integrated Beam Expanders Coupled to Flat Fibers

We find by transmission electron diffraction (TED) that the orthorhombic splitting of the upper surface layers ( μm) of single crystal Ba 2 YCu 3 O 7-δ (YBCO) is reduced, differing by 10 to 30 percent from the bulk value. We also find by transmission electron microscopy (TEM) that in general the surfaces are of inferior quality, and thus, not representative of the bulk. These results have important consequences for those experiments that probe only the upper surface layers. By etching with either Br/ethanol or HClO 4 /NaClO 4 the poor quality surfaces can be removed.

Orthorhombic Splitting and Chemical Etching of Ba2Ycu3O7-δ Crystal Surfaces

We present the transverse mode and temperature characteristics of a novel InGaAsP (1.3 /spl mu/m) vertical cavity laser structure which employs a lattice mismatched GaAs/AlAs mirror and one dielectric mirror. The devices lase in a linearly polarized, single transverse mode up to 2 times threshold. The characteristic temperature of 11 /spl mu/m diameter devices is 67 K at room temperature. >

Temperature and transverse mode characteristics of InGaAsP (1.3 /spl mu/m) vertical cavity lasers on GaAs substrates

Untersuchung der korrosionsgeschwindigkeiten und teilstroeme von cu und cu‐30zn‐leg. in sauerstoffhaltigen chloridloesungen mit der rotierenden ring‐scheibenelektrode

A monolithically integrated photonic circuit with an InGaAs / InGaAsP multiple-quantum-well (MQW) traveling- wave optical amplifier, a Brag reflection grating-folded noise filter, and an MQW photodetector has been demonstrated. This photonic circuit offers potential as a preamplfiied lightwave receiver.

http://ieeexplore.ieee.org/iel3/68/6610/00262554.pdf

Barry Miller

Papers

Semiconductor Optical Amplifier Array with Integrated Beam Expanders Coupled to Flat Fibers

Orthorhombic Splitting and Chemical Etching of Ba2Ycu3O7-δ Crystal Surfaces

Temperature and transverse mode characteristics of InGaAsP (1.3 /spl mu/m) vertical cavity lasers on GaAs substrates

Untersuchung der korrosionsgeschwindigkeiten und teilstroeme von cu und cu‐30zn‐leg. in sauerstoffhaltigen chloridloesungen mit der rotierenden ring‐scheibenelektrode

Integrated MQW Optical Amplifier/Noise-Filter/Photodetector