Photoconductivity and carrier transport process in poly(p-phenylene vinylene) film

Takiguchi, T.; Park, D.H.; Ueno, H.; Yoshino, Katsumi; Sugimoto, Ryuichi

doi:10.1016/0379-6779(87)90815-0

Cited by 82 publications

(28 citation statements)

References 3 publications

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“…27 In more direct, time-of-flight (TOF) studies of solid PPV samples the major carrier has been shown to be the hole with a mobility in the range 10 -7 -10 -8 m 2 /Vs. 4,5 In separate pulse-radiolysis TRMC experiments on solid samples, we have also found mobility values close to 10 -7 m 2 /V s. 28 The values for solid samples are seen to be similar to the minimum mobility estimated for the gel in the present work, indicating that the same mechanism of charge transport is probably operative and that the quantum yield for polaron pair formation in the gel is ca. 20% and possibly even larger.…”

Section: Resultssupporting

confidence: 81%

Polaron Pair Formation, Migration, and Decay on Photoexcited Poly(phenylenevinylene) Chains

1996

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Poly(2-(3,7-dimethyloctoxy)-5-methoxy-1,4-phenylenevinylene), (dMOM-PPV), undergoes a thermochromic transition on heating in benzene at approximately 35°C from a red gel to a yellow solution. The latter is metastable on cooling to room temperature and eventually reverts to the gel form after several hours. The absorption and emission spectrum of the gel can be resolved into two components, one which is identical with that for the solution and which is therefore associated with single-strand segments, and a second of similar spectral shape but lower energy which is ascribed to aggregated segments. Photoexcitation of dMOM-PPV in both the gel and solution results in a transient change in the microwave conductivity as monitored using the time-resolved microwave conductivity (TRMC) technique. The change in microwave conductivity for the gel is approximately an order of magnitude larger than for the solution. No TRMC transient is found on flash photolysis of a benzene solution of a dMOM-PPV derivative with 13% nonconjugated units in the polymer backbone. The effects are attributed to formation of mobile charge carriers (polaron pairs) on a single polymer chain in the case of the solution, whereas in the gel interchain charge transfer results in the predominant formation of charge carriers located on separated chains. The product of the quantum efficiency for polaron pair formation, φ p , and the sum of the mobilities, Σµ, is φ p Σµ ) (2.0 ( 0.3) × 10 -8 m 2 /Vs and (2.0 ( 0.5) × 10 -9 m 2 /Vs for the gel and solution respectively. The decay in microwave conductivity is nonexponential and extends to hundreds of nanoseconds.

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Section: Resultssupporting

confidence: 81%

Polaron Pair Formation, Migration, and Decay on Photoexcited Poly(phenylenevinylene) Chains

1996

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“…3,[9][10][11] The TOF measurements invariably display very disperse displacement currents with only slight evidence, if any, of Gaussian transport with a well-defined drift time in any of the samples studied. This can be explained by the complex morphology of the materials and the lack of monodomain samples with dimensions of tens of microns.…”

Section: Resultsmentioning

confidence: 96%

“…The mobility values, if obtainable at all, may therefore be considered to also be lower limits to the values which pertain at short times within well-organized monodomains of the material. Accordingly, the maximum TOF mobilities found for PPV or its derivatives are on the order of 10 -7 m 2 /(V s) or less, 3,10,11 i.e., considerably lower than the estimates from time-resolved conductivity measurements at short times based on φ p ) 0.01. In the majority of TOF studies the hole has been identified as the major charge carrier for times on the order of a microsecond or longer after photoionization.…”

Section: Introductionmentioning

confidence: 90%

Charge Carrier Dynamics in Pulse-Irradiated Polyphenylenevinylenes: Effects of Broken Conjugation, Temperature, and Accumulated Dose

Warman

1996

J. Phys. Chem.

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The transient conductivity resulting from nanosecond pulsed ionization of alkoxy-substituted phenylenevinylene/ethylidene copolymers, "dMOM-PPV(n)", with n the fractional vinylene content, has been studied using the pulse radiolysis time-resolved microwave conductivity (PR-TRMC) technique. Minimum values of the sum of the charge carrier mobilities within the bulk solids, ∑µ min , have been estimated from the endof-pulse conductivity. For the freshly precipitated materials at room temperature, ∑µ min decreases gradually with decreasing n from 1.8 × 10 -7 m 2 /(V s) for n ) 1 (full conjugation) to 0.4 × 10 -7 m 2 /(V s) for n ) 0.57. After annealing dMOM-PPV(1) at 100 and 150°C, ∑µ min at room temperature increased to 3.2 × 10 -7 and 8.0 × 10 -7 m 2 /(V s), respectively. No significant effect of high-temperature annealing was found for n e 0.87. On cooling dMOM-PPV(1) from 150 to -50°C, ∑µ min decreased initially with an activation energy of approximately 0.07 eV but approached a plateau at the lowest temperatures. The after-pulse decay of the conductivity was disperse in all cases. First half-lives of several microseconds were found for n ) 1. The decay kinetics were independent of the dose in the pulse. Large accumulated radiation doses (up to 1.2 MJ/kg) did not effect the end-of-pulse conductivity but did increase the decay rate. This effect could be reversed by high-temperature annealing.

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“…The Cambridge group references its PPV with a very low dark carrier concentration and consequently the formation of Schottky barriers at the PPV/Al interface is not expected. The mobility of the holes was measured at 10 -4 cm 2 V -1 s -1 [62] and that for the electrons is expected to be clearly lower.…”

Section: Metal/conjugated Polymer Contactsmentioning

confidence: 99%

Conjugated Polymer‐Based Plastic Solar Cells

Brabec

Sariçiftçi

1999

Semiconducting Polymers

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A tremendous research effort was devoted to the development of photovoltaic cells during the late seventies and early eighties. During this time interest was also devoted to the development of organic semiconductors, because they offer the advantages of low cost and facile processing. Organic materials for use in photovoltaic devices require a good chemical stability and large optical absorption in the visible range. For this purpose the first studied compounds were merocyanines [1] and phthalocyanines [2], which can readily be deposited as a thin film on various even flexible substrates by vacuum evaporation. Power conversion efficiencies of such devices are about 1% for small size photovoltaic elements.It is indeed intriguing and economically advantageous to think of large area photovoltaic elements based on thin plastic films, cut from rolls and deployed on permanent structures and surfaces. In order to fulfil these low cost and large area requirements, cheap production technologies for large scale coating must be used together with low cost material. Polymer photovoltaic cells hold the potential for such low cost cells. The flexibility of chemical tailoring of desired properties, as well as the cheap technology already well developed for all kinds of plastic thin film applications, meet exactly the above mentioned demands for cheap photovoltaic device production. The mechanical flexibility of plastic materials is useful for all photovoltaic applications onto curved surfaces for indoor as well as outdoor applications.Efficiencies of the first polymeric solar cells, based on hole conducting conjugated polymers (mainly polyacetylene) were rather discouraging [3]. However, the breakthrough to higher efficiencies was achieved by switching to different classes of electron-donor type-conjugated polymers (polythiophenes (PT), poly(para-phenylene vinylene)s (PPV) and their derivatives) and by mixing them with suitable electron acceptors [4]. Prototypes of photovoltaic devices based on a polymeric donor/acceptor networks showed solar energy conversion efficiencies of around 1% [5]. In particular, the photovoltaic properties and the photophysics of conjugated polymer/fullerene solid composites have been well investigated over the last few years [6].Besides the necessity for improvement in efficiency, stability is another problem for all the applications of conjugated polymers. First experiences on conjuSemiconducting Polymers: Chemistry, Physics and Engineering. Edited by G. Hadziioannou and P. F. van Hutten

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Photoconductivity and carrier transport process in poly(p-phenylene vinylene) film

Cited by 82 publications

References 3 publications

Polaron Pair Formation, Migration, and Decay on Photoexcited Poly(phenylenevinylene) Chains

Polaron Pair Formation, Migration, and Decay on Photoexcited Poly(phenylenevinylene) Chains

Charge Carrier Dynamics in Pulse-Irradiated Polyphenylenevinylenes: Effects of Broken Conjugation, Temperature, and Accumulated Dose

Conjugated Polymer‐Based Plastic Solar Cells

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