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

Summary form only given In summary, a Mach-Zehnder WDM fibre network wavelength converter with variable input and output wavelengths has been presented The integrated signal and probe pre-amplifiers potentially reduce input power requirements Around 25-dB extinction ratio has been demonstrated, as well as operation at 25 Gbit/s

Mach-Zehnder wavelength converter with integrated preamplifiers

Erratum: Electric field screening by photogenerated holes in multiple quantum wells: A new mechanism for absorption saturation [Appl. Phys. Lett. 57, 1081 (1990)]

An increase in the solar-to-electrical conversion efficiency beyond that due to chemisorption of ruthenium results from subsequent adsorption of lead from alkaline solutions on both single crystal and polycrystalline n-GaAs photoanodes. An efficiency of 7.8% is reached with thin film, chemically vapor deposited polycrystalline GaAs in the cell n-GaAs/0.8 M K2Se0.1 M K2Se21 M KOH/C.



Eine Erhohung des Wirkungsgrades sowohl einkristalliner als auch polykristalliner n-GaAs-Photoanoden uber den durch Chemisorption von Ruthenium erreichten Wert wird beobachtet, wenn nachfolgend Blei aus alkalischer Losung auf der Elektrode adsorbiert wird. An polykristallinem, durch chemischen Transport hergestelltem GaAs wird mit dem kombinierten Verfahren in der Zelle n-GaAs/0.8 M K Se 0,1 M K2Se2 1 M KOH/C ein Wirkungsgrad von 7,8% erreicht.

Combined ruthenium lead surface treatment of gallium arsenide photoanodes

The performance of an optical power amplifier used, for example, as the output stage in an optical transmitter1 is usually limited by gain nonlinearities rather than the gain level. Recently,2 we demonstrated high saturation output power (~45 mW) at moderate gain levels (13.5 dB) in a 1.5-µm optical amplifier with a multiple quantum well (MQW) active region. The large saturation power in a MQW amplifier is due to the small confinement factor and short gain recovery time. (The saturation power is Inversely proportional to both.) MQW amplifiers are particularly attractive when they are integrated with other optical devices as part of a photonic integrated circuit.1

Barry Miller

Papers

Mach-Zehnder wavelength converter with integrated preamplifiers

Erratum: Electric field screening by photogenerated holes in multiple quantum wells: A new mechanism for absorption saturation [Appl. Phys. Lett. 57, 1081 (1990)]

Combined ruthenium lead surface treatment of gallium arsenide photoanodes

Gain saturation characteristics of 1.5-jum multiple quantum well optical amplifiers

Rotating electrode d.c. solution conductivity device