Electrochemically Monitored Photoluminescence of Conjugated Polymers

Montilla, F.; Huerta, Francisco

doi:10.1007/978-3-319-49137-0_4

Cited by 8 publications

(7 citation statements)

References 124 publications

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“…The main absorption peak at 642 nm and shoulders at around 590 and 540 nm are characteristic of hole polarons residing in the β-phase of PFO films . The main peak shows a linear increase with hole density up to 2 × 10 19 cm –3 , and this allows us to determine the absorption cross section of 4 × 10 16 cm 2 for hole polarons at 642 nm, which is consistent with the literature values. , This gives us independent verification of the charge densities in our experiments.…”

Section: Resultssupporting

confidence: 91%

“…16 The main peak shows a linear increase with hole density up to of 2×10 19 cm -3 and this allows us to determine the absorption cross-section of 4×10 16 cm 2 for hole polarons at 642 nm which is consistent with literature values. 16,18 This gives us independent verification of the charge densities in our experiments. The PL lifetime in undoped PFO film is 142 ps and similar to the previously found 170 ps PL lifetime in films with a high proportion of β-phase.…”

Section: Resultssupporting

confidence: 70%

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Exciton–Polaron Interactions in Polyfluorene Films with β-Phase

2018

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Fluorescence quenching by electric charges is an important loss mechanism in highbrightness organic light emitting diodes (OLEDs) but its effect is difficult to quantify in working devices. Here we combine an electrochemical technique to control the charge density with time-resolved photoluminescence to distinguish between different quenching mechanisms. The material studied was the blue electroluminescent polymer poly(9,9dioctylfluorenene) with β phase. Our results show that quenching occurs by Förster resonance energy transfer and is mediated by exciton diffusion. We determine the quenching parameters over a wide range of charge concentrations and estimate their impact on the OLED efficiency roll-off at high current density. We find that fluorescence quenching by charges and singlettriplet exciton annihilation are the two main mechanisms leading to the efficiency roll-off.Our results suggest that hole polarons are not very effective quenchers of singlet excitons which is important for understanding current devices and encouraging for the development of high-brightness OLEDs and lasers.

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Section: Resultssupporting

confidence: 91%

Section: Resultssupporting

confidence: 70%

Exciton–Polaron Interactions in Polyfluorene Films with β-Phase

2018

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“…The peak shis can have their origin in the effective conjugated length in the polymer. [24][25][26] Therefore; the same wavelength observed for the peaks shows equal effective conjugated length for both of the samples, being independent of APS to monomer molar ratio. The difference in PL spectra of the samples lays in the intensities of the peaks, which are higher for Pmic21.…”

Section: Thermal Analysismentioning

confidence: 53%

Continuous microfluidic fabrication of polypyrrole nanoparticles

2019

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“…57 However, at high-doping levels, the exciton−polaron annihilation is dominated by resonant energy transfer via dipole−dipole interaction, thus producing a better efficiency of the quenching process. 58 After the consumption of the excess of n-polarons, electrogenerated excitons are formed from the recombination of balanced concentrations of polarons with opposite sign, producing a maximum emission intensity. During the emission, n-polarons are completely consumed.…”

Section: Resultsmentioning

confidence: 99%

“…At low doping levels, the annihilation rate constant, k q , depends on the diffusion rate of the species implied in the annihilation process, excitons and quenchers57 . However at high-doping levels, the exciton-polaron annihilation is dominated by resonant energy transfer via dipole-dipole interaction thus producing a better efficiency of the quenching process 58. After the consumption of the excess of n polarons, electrogenerated excitons are formed from the recombination of balanced concentrations of polarons with opposite sign, producing a maximum emission intensity.…”

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confidence: 99%

Optimization of the Electrochemically Generated Luminescence of Polyfluorene Films

2018

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Electrochemically-generated chemiluminescence (ECL) from solid-state poly(9,9'octylfluorene) films was obtained by the successive electrochemical injection of polarons with opposite sign (annihilation ECL) in double potential steps. The processes involved in the recombination of polarons, the quenching of the electrochemically generated excitons and the emission stability have been also analysed. A systematic study at various electrochemical potentials has been carried out to determine optimal conditions to obtain a maximum ECL intensity, particularly with potentials of 0.4 V beyond the doping onsets (for both p and n doping). Results show that while the ECL emission is slightly affected by the potential of the emission, it is strongly dependent on the charging potential. Under large charging potential the electrochemically generated excitons formed in the emission step get quenched by an excess of polarons and bipolarons that are in detrimental of ECL. The maximum emission is obtained when the applied potentials are 0.4 V over the doping onset of the polymer conjugated chain. After partial depletion of the excess of polarons, the emission coming from the recombination of balanced polarons of opposite sign is observed. The stability of ECL emission in the optimal range was determined in continuous cathodic-anodic pulses. A rapid loss of the intensity in the initial stages is observed due to the dissolution of low molecular weight polymer fragments, that become soluble upon electrochemical doping. The emission spectrum remains stable during the complete lifetime of the polymer. The spectral shape of PFO films indicates that the emission occurs mainly from the β-phase domains in which the electrochemical charge is preferentially injected.

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Electrochemically Monitored Photoluminescence of Conjugated Polymers

Cited by 8 publications

References 124 publications

Exciton–Polaron Interactions in Polyfluorene Films with β-Phase

Exciton–Polaron Interactions in Polyfluorene Films with β-Phase

Continuous microfluidic fabrication of polypyrrole nanoparticles

Optimization of the Electrochemically Generated Luminescence of Polyfluorene Films

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