Photoinduced Enhancement of Photoluminescence Intensity in PPV Films

2001 ◽  
Vol 665 ◽  
Author(s):  
Yara Galvão Gobato ◽  
Alexandre Marletta ◽  
Jucimar M. Souza ◽  
Ernesto Pereira ◽  
Roberto M. Faria ◽  
...  
Keyword(s):  
Laser Power ◽  
Blue Shift ◽  
Sample Thickness ◽  
Phenylene Vinylene ◽  
Photoluminescence Intensity ◽  
Carbonyl Groups ◽  
Conjugation Length ◽  
Ion Laser ◽  
Pl Intensity ◽  
Effective Conjugation Length

ABSTRACTPoly(p-phenylene vinylene) (PPV) films are usually photodegraded in air. We report on the enhancement of photoluminescence (PL) intensity of PPV films induced by Ar ion laser in the presence of air. The PL spectra were measured as function of laser power, time exposure and sample thickness. The initial PL intensity increases up to 300% without significant changes in peak positions by optimizing such parameters. This effect is accompanied by a blue-shift in the absorption spectrum resulting in shortened effective conjugation length and by a formation of defects such as carbonyl groups. Mechanisms for the observed photoluminescence intensity enhancements are suggested.

Influence of Preliminary Plasma Processing on Luminescent Properties of Porous Silicon

2014 ◽  
Vol 213 ◽  
pp. 90-95
Author(s):  
Nikolay Gennadievich Galkin ◽  
Dmitrii Tkhyarbonovich Yan ◽  
Evgeniy Anatolievich Chusovitin ◽  
Anton Borisovich Rasin ◽  
Konstantin Nikolaevich Galkin ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Plasma Treatment ◽  
Spectral Composition ◽  
Silicon Layer ◽  
Luminescent Properties ◽  
Blue Shift ◽  
Porous Silicon Layer ◽  
Radiative Properties ◽  
Photoluminescence Intensity ◽  
Pl Intensity

Measurements of radiative properties of porous silicon after compression plasma treatment have been carried out. Significant increase of photoluminescence intensity and blue shift of spectra have been observed on studied samples in comparison with porous layers formed on monocrystalline silicon without preliminary plasma treatment. An influence of long storage of plasma modified porous silicon layer on the intensity and spectral composition of photoluminescence has been checked. A rise of PL intensity during first moth of storage and following decrease of PL intensity in the next three months has been observed. Mechanisms of changes in a spectral composition of PL and alterations of PL intensity during storage have been discussed.

Study on effect of supercritical CO2 on structural ordering and charge transporting property in thiophene-based block copolymer

2022 ◽  
Author(s):  
Satomi Hosokawa ◽  
Eri Tomita ◽  
Shinji Kanehashi ◽  
Kenji Ogino
Keyword(s):  
Supercritical Co2 ◽  
Hole Mobility ◽  
Amorphous Region ◽  
Crystalline Region ◽  
Space Charge Limited Current ◽  
Conjugation Length ◽  
Enhanced Mobility ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Effective Conjugation Length

Abstract We reported that supercritical (sc) annealing of poly(3-hexylthiophene) (P3HT), and its block copolymers with poly(ethylene oxide) (PEO) and polystyrene (PSt) brought about improvements in the crystal structure and hole mobility, determined by the space charge limited current (SCLC) measurement. P3HT-b-PEO showed the largest increase in mobility. From XRD profile, it was found that the treatment with scCO2 increased the crystallite size and crystallinity. UV-vis spectra showed that the effective conjugation length in the scCO2 treated films was increased compared to the as-spun, suggesting that CO2 molecules are incorporated into domains of the second block domains and P3HT amorphous region, and assist to alter the characteristics of the crystalline region. Then, it was considered that the change in the crystalline structure and the improvement of P3HT chains packing led to the enhanced mobility. Since PEO is known to have a higher affinity for CO2, the increase of mobility was specifically intensive.

A Self-Threading Polythiophene: Defect-Free Insulated Molecular Wires Endowed with Long Effective Conjugation Length

2010 ◽  
Vol 132 (42) ◽  
pp. 14754-14756 ◽  
Author(s):  
Kazunori Sugiyasu ◽  
Yoshihito Honsho ◽  
Ryan M. Harrison ◽  
Akira Sato ◽  
Takeshi Yasuda ◽  
...  
Keyword(s):  
Molecular Wires ◽  
Conjugation Length ◽  
Effective Conjugation Length

Laser-Induced Dry Etching of GaAs with High Aspect Ratio

1991 ◽  
Vol 236 ◽  
Author(s):  
Cheon Lee ◽  
Hirokazu Sayama ◽  
Susumu Namba ◽  
Mikio Takai
Keyword(s):  
Aspect Ratio ◽  
Electron Spectroscopy ◽  
Laser Power ◽  
Chemical Compositions ◽  
Reaction Products ◽  
Scan Speed ◽  
Ion Laser ◽  
Etched Surface ◽  
Argon Ion ◽  
Scattering Measurement

AbstractLaser-induced thermochemical reactions have been investigated for GaAs in a CCl2F2 gas ambient using an argon-ion laser. The chemical compositions of the reaction products deposited on the etched groove were measured by Auger electron spectroscopy (AES). The conditions of laser power, scan speed, and CC12F2 gas pressure under which the etching reaction occurs without deposition of the residue were clarified. High etching rates up to 267 μm/s and an aspect ratio of 4.5 have been achieved by a single scan of a laser beam. Microprobe photoluminescence and Raman scattering measurement were carried out on the etched surface to characterize damage induced by this processing.

Stability of PPV Derivatives: The Effect of Side Group Functionalities

1995 ◽  
Vol 413 ◽  
Author(s):  
B. H. Cumpston ◽  
K. F. Jensen ◽  
F. Klavettert ◽  
E. G. J. Staring ◽  
R. C. J. E. Demand
Keyword(s):  
Double Bond ◽  
Singlet Oxygen ◽  
Degradation Pathway ◽  
Phenylene Vinylene ◽  
Conjugation Length ◽  
Trans Stilbene ◽  
Thin Polymer ◽  
Singlet Oxygen Reaction ◽  
Semi Empirical

ABSTRACTWe have identified excited-state singlet oxygen as a reactive intermediate in the solid state photo-oxidation of two poly(p-phenylene vinylene) (PPV) derivatives, poly(2,5-bis(5,6- cholestanoxy)-1,4-phenylene vinylene) (BCHA-PPV) and poly(2-methoxy,5-(2'-ethyl-hexoxy)- 1,4-phenylene vinylene) (MEH-PPV). Singlet oxygen is photosensitized via energy transfer from the polymer and undergoes 1,2-cycloaddition across the electron-rich vinyl double bond in the backbone of the polymer resulting in the formation of highly oxidized species such as esters. Volatile carbonyl species are also formed, and, consequently, the film thins. This degradation pathway occurs when the polymer film is exposed in air to light having energy above the bandgap of the polymer, from either a low-pressure UV mercury lamp or an Ar+ laser operating at 514 or 457 nm. Interestingly, the singlet oxygen reaction does not take place in model compounds with similar structures such as trans-stilbene. In an effort to understand which properties of the polymer make it susceptible to singlet oxygen attack, we have studied the effect of conjugation length and side groups on the reactivity of thin polymer films. Specifically, the role of electron withdrawing groups, steric protection of the vinyl double bond, and conjugation length effects have been investigated using both FrIR spectroscopy and semi-empirical computational chemistry calculations.

scholarly journals Nonlinear correlations between ν1 Raman band and global scalar properties for different length carotenoids

2019 ◽  
Vol 58 (4) ◽  
Author(s):  
Mindaugas Mačernis
Keyword(s):  
Linear Dependence ◽  
Density Functional ◽  
Chemical Potential ◽  
Raman Band ◽  
Conjugation Length ◽  
Electrophilicity Index ◽  
Special Groups ◽  
Scalar Properties ◽  
Nonlinear Correlations ◽  
Effective Conjugation Length

The Raman ν1 band corresponding to the polarization of various length carotenoid (Car) and polyene molecules was theoretically analysed using the density functional theory (DFT) approach. The polarization and other properties of Car and polyene monomers were estimated by using global scalar properties. The results demonstrate a linear dependence between the frequency of the so-called ν1 Raman band corresponding to the C=C stretching modes, and the global hardness (and global softness) for all molecules of different conjugation lengths. Linear correlations between all global scalar properties and the conjugation length were for polyene structures only. From these calculations an additional relationship was also identified: upon s-cis-isomerisation the effective conjugation length and global softness increased for polyenes, while the effective conjugation length and global softness decreased for carotenoids containing β-rings at their ends. According to the electrophilicity index study, charge transfer processes (CT) should be favourable in longer carotenoid and polyene structures. A linear dependence of electronegativity was found for polyene and particular Cars subgroups. The electrophilicity index was very sensitive to special groups bonded to the polyene chain of Cars. Finally, the conjugation length of the Cars did not have a linear dependence on the electronegativity, chemical potential and electrophilicity index, but almost a linear dependence was seen on the global hardness while the polyene models had a linear dependence in all cases.

Sign in / Sign up

Export Citation Format

Share Document