Recombination Kinetics (recombination + kinetics)

Distribution by Scientific Domains


Selected Abstracts


The Effect of Polymer Optoelectronic Properties on the Performance of Multilayer Hybrid Polymer/TiO2 Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2005
P. Ravirajan
Abstract We report a study of the effects of polymer optoelectronic properties on the performance of photovoltaic devices consisting of nanocrystalline TiO2 and a conjugated polymer. Three different poly(2-methoxy-5-(2,-ethylhexoxy)-1,4-phenylenevinylene) (MEH-PPV)-based polymers and a fluorene,bithiophene copolymer are compared. We use photoluminescence quenching, time-of-flight mobility measurements, and optical spectroscopy to characterize the exciton-transport, charge-transport, and light-harvesting properties, respectively, of the polymers, and correlate these material properties with photovoltaic-device performance. We find that photocurrent is primarily limited by the photogeneration rate and by the quality of the interfaces, rather than by hole transport in the polymer. We have also studied the photovoltaic performance of these TiO2/polymer devices as a function of the fabrication route and device design. Including a dip-coating step before spin-coating the polymer leads to excellent polymer penetration into highly structured TiO2 networks, as was confirmed through transient optical measurements of the photoinduced charge-transfer yield and recombination kinetics. Device performance is further improved for all material combinations studied, by introducing a layer of poly(ethylene dioxythiophene) (PEDOT) doped with poly(styrene sulfonic acid) (PSS) under the top contact. Optimized devices incorporating the additional dip-coated and PEDOT:PSS layers produced a short-circuit current density of about 1,mA,cm,2, a fill factor of 0.50, and an open-circuit voltage of 0.86,V under simulated AM,1.5 illumination (100,mW,cm,2, 1,sun). The corresponding power conversion efficiency under 1,sun was ,,0.4,%. [source]


Determination of carrier diffusion coefficient and lifetime in single crystalline CVD diamonds by light-induced transient grating technique

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2010
T. Malinauskas
Abstract We report on a contactless, all-optical study of carrier diffusion and recombination kinetics in single-crystalline diamond layers using the light-induced transient grating (LITG) technique. Decay times of transient diffraction grating yielded carrier lifetime of ,R,,,3,ns and bipolar diffusion coefficient Da,=,12,cm2/s at 300,K. The latter value of Da was found to be 4,5 times lower than the ambipolar diffusivity based on electron and hole mobilities, measured by photo-electrical time-of-flight (ToF) technique. This discrepancy was attributed to the bandgap renormalization at high excess carrier densities and its impact on carrier diffusion. The significant decrease of low temperature diffusivity pointed out to a contribution of many-body effects which are tentatively attributed to the formation of electron,hole liquid (EHL) at T,<,150,K. [source]


Temperature dependence of the photoluminescence of single GaAs/AlGaAs concentric quantum ring structure

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2006
M. Bonfanti
Abstract We present the temperature dependence of the photoluminescence emission of single concentric quantum rings. The two rings which form the nanostructure show a decoupled recombination kinetics in the whole temperature range. The emission is characterized by a doublet. The emission linewidth, which is already larger than 1 meV at low temperatures and increases as the temperature raises, is dominated by the thermal activation of carriers to higher excited states. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Kinetics of optically excited charge carriers and defects in hydrogenated amorphous silicon and related alloys

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2004
J. Whitaker
Abstract Electron spin resonance and optically induced electron spin resonance measurements on hydrogenated amorphous silicon and germanium are useful probes of charge carriers in localized electronic states near the edges of the conduction and valence bands (band-tail states) and of defects, such as silicon and germanium dangling bonds. We review recent results on the recombination kinetics of charge carriers trapped in band-tail states. We also review recent results on the kinetics of metastable optically induced germanium dangling bonds in hydrogenated amorphous germanium. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Kinetics of radiative recombination of the "pseudo-donor,pseudo-acceptor" pairs in InGaN/GaN

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2004
A. J. Zakrzewski
Abstract It was shown that the recombination kinetics of electrons and holes localized on potential fluctuations in quantum wells could be calculated exactly in terms of hypergeometric functions. Our algorithms are much easier for coding and much faster and more accurate then previously developed. Moreover, our approach enables real time processing of experimental data. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Characteristics of Photoexcitations and Interfacial Energy Levels of Regioregular Poly(3-hexythiophene-2,5-diyl) on Gold,

CHEMPHYSCHEM, Issue 13 2007
Youngku Sohn Dr.
Abstract We have studied characteristics of photoexcitations and interfacial electronic structures of regioregular poly(3-hexlythiophene-2,5-diyl) (P3HT) on gold using two-photon photoemission (2PPE) spectroscopy. The vacuum level threshold is decreased by 1.3 eV from that of bare gold, attributable to interface dipole effects. The 2PPE spectral width narrows as the film thickness increases. We tentatively understand that this is due to destabilization of long-lived localized polaron, attributed to strong interchain interactions. On the basis of the analysis of the 2PPE distribution as a function of photon energy and laser power, the polaron level is located at 3.1 eV below the vacuum level. Using this value and a polaron level of 1.75 eV above the HOMO, we indirectly estimate an ionization potential of 4.85 eV for P3HT. An increase in two-photon photoemission yield with increasing photon energy is attributed to an enhanced electron-hole pair dissociation yield at higher photo-excitation levels. The decrease in power law slope with increasing film thickness is understood by Langevin recombination kinetics and saturation of photoexcitations [source]