Photoconductivity in Langmuir—Blodgett multilayer structures of phthalocyaninato-polysiloxane

Gattinger, P.; Rengel, H.; Neher, Dieter

doi:10.1016/s0379-6779(96)04490-6

Cited by 14 publications

(8 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Current-voltage (I-V) characteristics were recorded in dry nitrogen atmosphere in a temperature stabilized setup 19 . For experiments under illumination a 689 nm diode laser with a photon flux of about 5×10 17 photons/cm 2 s was used.…”

Section: Methodsmentioning

confidence: 99%

<title>Photoconductivity and charge-carrier photogeneration in photorefractive polymers</title>

Daeubler¹,

Kulikovsky²,

Neher³

et al. 2002

SPIE Proceedings

View full text Add to dashboard Cite

We have studied photogeneration, transport, trapping and recombination as the governing mechanisms for the saturation field strength and the time response of the photorefractive (PR) effect in PVK-based PR materials, utilizing xerographic discharge and photoconductivity experiments. Both the charge carrier photogeneration efficiency and the photocurrent efficiency were found to be independent of chromophore content, suggesting that the chromophore does not participate in carrier generation and trapping. The photoconductivity gain factor G defined as the number of charge carriers measured in photoconductivity in relation to the number of carriers initially photogenerated as determined by the xerographic experiments is found to be much smaller than unity, which indicates that the mean free path of the photogenerated charge carriers is less than the grating period. Photoconductivity data can be explained over 3 orders of magnitude in field, assuming a field-independent trap density. Based on the photoelectric data, PR response times have been predicted by Yeh's model for the build-up of space or by calculating the time, which is necessary to fill all traps by photogenerated holes. Only the latter model can reasonably well explain the observed field dependence of the PR growth time, suggesting that trap -filling essentially controls the PR onset behaviour.

show abstract

Section: Methodsmentioning

confidence: 99%

<title>Photoconductivity and charge-carrier photogeneration in photorefractive polymers</title>

Daeubler¹,

Kulikovsky²,

Neher³

et al. 2002

SPIE Proceedings

View full text Add to dashboard Cite

show abstract

“…22 The spectral intensity variation of the xenon lamp that was used for illumination was corrected such that a constant photon flux of about 10 13 ph/cm 2 sec was established at the film side facing the light source. Data were recorded pointwise and refer to photocurrents established after 80 sec illumination.…”

Section: Methodsmentioning

confidence: 99%

Efficient bulk photogeneration of charge carriers and photoconductivity gain in arylamino-PPV polymer sandwich cells

et al. 1999

Self Cite

View full text Add to dashboard Cite

Stationary photoconductivity has been measured for sandwich cells of poly͑phenylimino-1,4-phenylene-1,2ethenylene-2,5-dioctyloxy-1,4-phenylene-1,2-ethenylene-1,4-phenylene͒ between gold and aluminum electrodes. Films with thicknesses below and above 1 m were examined in order to separate photocurrent contributions arising from processes at the polymer/electrode interfaces and the bulk. Spectra recorded under forward bias were almost identical in shape and size for irradiation through either the anode or the cathode indicating that the photocurrent is dominated by bulk photogeneration of charge carriers. Large charge carrier collection efficiencies exceeding those of typical PPV derivatives are derived from these experiments. The photogeneration is clearly enhanced within the tail of the polymer absorption and photoaction spectra recorded under forward bias resemble well the shape of solid-state photoexcitation spectra. We presume that both photoluminescence and photoconductivity in the studied arylamino-PPV compound are dominated by the excitation of states or sites rather deep in the density of states distribution. Under reverse bias the photoaction spectra depend strongly on illumination conditions. For illumination through the positively biased aluminum electrode the photocurrent spectra are almost symbatic with the polymer absorption while antibatic behavior is observed upon illumination through the gold electrode. The data can qualitatively be explained by the buildup of a negative space-charge region by immobile photogenerated electrons. Upon illumination through the positively biased aluminum electrode collection efficiencies of up to 2000% are observed. This is attributed to photocurrent multiplication arising from the accumulation of electrons near the interface, which promotes tunneling of holes into the film.

show abstract

“…(Phthalocyaninato)polysiloxane (PcPSi) composed of siloxane-polymerized, cofacially stacked phthalocyanines (Pc), staggered at an angle of 36°, is a one-dimensional molecular conductor . The linear stacking and the rather small ring−ring interplanar spacing of about 0.33 nm − favor efficient intermacrocycle π−π interactions, so that optical excitation is expected to lead to extensive excitonic coupling between the extended π-conjugated electron systems of the phthalocyanine cycles. ,, In particular, Langmuir−Blodgett multilayer structures of PcPSi exhibit high photoconductivity and strong light absorption in the visible, properties that are the basis for the successful development of photoactive devices such as photodiodes and sensors. , The photogeneration of charges in PcPSi films has been the subject of intense research for many years. ,− There are several issues of central importance in studying the photogeneration of charge carriers as well as the transport dynamics of excited states and charge carriers. The proper characterization of the relaxation dynamics of the initially excited electronic states and, in particular, of the exciton transport dynamics is of great interest in this regard.…”

Section: Introductionmentioning

confidence: 99%

“…1 The linear stacking and the rather small ring-ring interplanar spacing of about 0.33 nm [1][2][3] favor efficient intermacrocycle π-π interactions, so that optical excitation is expected to lead to extensive excitonic coupling between the extended π-conjugated electron systems of the phthalocyanine cycles. 2,4,5 In particular, Langmuir-Blodgett multilayer structures of PcPSi exhibit high photoconductivity and strong light absorption in the visible, properties that are the basis for the successful development of photoactive devices such as photodiodes and sensors. 6,7 The photogeneration of charges in PcPSi films has been the subject of intense research for many years.…”

Section: Introductionmentioning

confidence: 99%

“…6,7 The photogeneration of charges in PcPSi films has been the subject of intense research for many years. 2,[4][5][6][7][8] There are several issues of central importance in studying the photogeneration of charge carriers as well as the transport dynamics of excited states and charge carriers. The proper characterization of the relaxation dynamics of the initially excited electronic states and, in particular, of the exciton transport dynamics is of great interest in this regard.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Femtosecond Study of Exciton Transport Dynamics in (Phthalocyaninato)polysiloxane

et al. 1999

View full text Add to dashboard Cite

The transport and relaxation dynamics of singlet excitons of rodlike [tetramethoxytetrakis(octyloxy)phthalocyaninato]polysiloxane (PcPSi) in tetrahydrofuran solution were investigated on the femtosecond scale by transient absorption spectroscopy. Singlet excitons are generated upon excitation into the ground-state absorption at 555 nm using laser pulses of 120 fs duration with different intensities. Transient absorption spectra were recorded at variable delays using a white-light continuum probe pulse. Both photoinduced bleaching and transient absorption show nonexponential decay dynamics with a pronounced dependence on the excitation energy density. The analysis of the decay dynamics of the photoinduced bleaching and transient absorption at lower excitation densities is made by including, in addition to the monomolecular, exponential decay with lifetime τ, a time-dependent bimolecular exciton−exciton annihilation rate constant γt -1/2, characteristic of one-dimensional diffusive exciton transport. At high excitation densities, the observed decay strongly deviates from this behavior, as a new relaxation channel is opened, which is attributed to short-lived, charge-separated states.

show abstract

Photoconductivity in Langmuir—Blodgett multilayer structures of phthalocyaninato-polysiloxane

Cited by 14 publications

References 12 publications

<title>Photoconductivity and charge-carrier photogeneration in photorefractive polymers</title>

<title>Photoconductivity and charge-carrier photogeneration in photorefractive polymers</title>

Efficient bulk photogeneration of charge carriers and photoconductivity gain in arylamino-PPV polymer sandwich cells

Femtosecond Study of Exciton Transport Dynamics in (Phthalocyaninato)polysiloxane

Contact Info

Product

Resources

About