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Journal ArticleDOI

Electron transport in copper phthalocyanines

22 Feb 2010-Journal of Applied Physics (American Institute of Physics)-Vol. 107, Iss: 4, pp 044509
TL;DR: In this article, the charge transport in copper phthalocyanine (CuPc), partially fluorinated CuPc (F4cuPc) and fluorinated F16cuPC based organic thin film transistors is studied using dual SiO2/polymethylmethacrylate gate dielectrics.
Abstract: Charge transport in copper phthalocyanine (CuPc), partially fluorinated CuPc (F4CuPc), and fluorinated CuPc (F16CuPc) based organic thin film transistors is studied using dual SiO2/polymethylmethacrylate gate dielectrics. We demonstrate the strong influence of air/moisture induced electron traps on electron transport when the lowest unoccupied molecular orbital is close to the vacuum irrespective of hydroxyl-free dielectrics used in the devices.
Citations
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TL;DR: This review summarizes the developments in small molecular donors, acceptors, and donor-acceptor dyad systems for high-performance multilayer, bulk heterojunction, and single-component OPVs and focuses on correlations of molecular chemical structures with properties, such as absorption, energy levels, charge mobilities, and photovoltaic performances.
Abstract: Organic photovoltaic cells (OPVs) are a promising cost-effective alternative to silicon-based solar cells, and possess light-weight, low-cost, and flexibility advantages. Significant progress has been achieved in the development of novel photovoltaic materials and device structures in the last decade. Nowadays small molecular semiconductors for OPVs have attracted considerable attention, due to their advantages over their polymer counterparts, including well-defined molecular structure, definite molecular weight, and high purity without batch to batch variations. The highest power conversion efficiencies of OPVs based on small molecular donor/fullerene acceptors or polymeric donor/fullerene acceptors are up to 6.7% and 8.3%, respectively, and meanwhile nonfullerene acceptors have also exhibited some promising results. In this review we summarize the developments in small molecular donors, acceptors (fullerene derivatives and nonfullerene molecules), and donor–acceptor dyad systems for high-performance multilayer, bulk heterojunction, and single-component OPVs. We focus on correlations of molecular chemical structures with properties, such as absorption, energy levels, charge mobilities, and photovoltaic performances. This structure–property relationship analysis may guide rational structural design and evaluation of photovoltaic materials (253 references).

1,515 citations

Journal ArticleDOI
TL;DR: In this article, a donor-acceptor polymer semiconductor (PDPP-TBT) was proposed for low-bandgap OTFTs with balanced hole and electron mobilities of 0.35 cm2 V1s-1 and 0.40 cm 2 V-1s -1, respectively.
Abstract: A new, solution-processable, low-bandgap, diketopyrrolopyrrole- benzothiadiazole-based, donor-acceptor polymer semiconductor (PDPP-TBT) is reported. This polymer exhibits ambipolar charge transport when used as a single component active semiconductor in OTFTs with balanced hole and electron mobilities of 0.35 cm2 V-1s-1 and 0.40 cm 2 V-1s-1, respectively. This polymer has the potential for ambipolar transistor-based complementary circuits in printed electronics.

406 citations

Journal ArticleDOI
TL;DR: In this article, the recent progress of copper complexes in the fields of organic light emitting devices (OLEDs), photovoltaic cells (dye-sensitized solar cells), and bulk heterojunction solar cells (BHJSCs) in the past two decades is presented.

138 citations

Journal ArticleDOI
TL;DR: Furan substituted diketopyrrolopyrrole (DBF) combined with benzothiadiazole based polymer semiconductor PDPP-FBF has been synthesized and evaluated as an ambipolar semiconductor in organic thin-film transistors.

85 citations

Journal ArticleDOI
TL;DR: In this paper, an organic thin film transistors (OTFTs) based on copper phthalocyanine (CuPc) having electrodes consisting of isolated carbon nanotube (CNT) arrays embedded in the organic layer are reported.
Abstract: We report on organic thin film transistors (OTFTs) based on copper phthalocyanine (CuPc) having electrodes consisting of isolated carbon nanotube (CNT) arrays embedded in the organic layer. CuPc OTFT with CNT array electrodes show p-type behavior with Ohmic hole injection, high hole mobility, and enhanced switching characteristics at low voltage. The p-type devices are converted to ambipolar OTFT by vacuum annealing. Despite the large offset between the CNT work function and the CuPc energy levels, electron injection characteristics are also Ohmic. The extension of CNT electrodes to the phthalocyanine family confirms the validity of this contact approach for organic electronic devices.

43 citations

References
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Journal ArticleDOI
10 Mar 2005-Nature
TL;DR: It is demonstrated that the use of an appropriate hydroxyl-free gate dielectric—such as a divinyltetramethylsiloxane-bis(benzocyclobutene) derivative (BCB; ref. 6)—can yield n-channel FET conduction in most conjugated polymers, revealing that electrons are considerably more mobile in these materials than previously thought.
Abstract: Organic semiconductors have been the subject of active research for over a decade now, with applications emerging in light-emitting displays and printable electronic circuits. One characteristic feature of these materials is the strong trapping of electrons but not holes1: organic field-effect transistors (FETs) typically show p-type, but not n-type, conduction even with the appropriate low-work-function electrodes, except for a few special high-electron-affinity2,3,4 or low-bandgap5 organic semiconductors. Here we demonstrate that the use of an appropriate hydroxyl-free gate dielectric—such as a divinyltetramethylsiloxane-bis(benzocyclobutene) derivative (BCB; ref. 6)—can yield n-channel FET conduction in most conjugated polymers. The FET electron mobilities thus obtained reveal that electrons are considerably more mobile in these materials than previously thought. Electron mobilities of the order of 10-3 to 10-2 cm2 V-1 s-1 have been measured in a number of polyfluorene copolymers and in a dialkyl-substituted poly(p-phenylenevinylene), all in the unaligned state. We further show that the reason why n-type behaviour has previously been so elusive is the trapping of electrons at the semiconductor–dielectric interface by hydroxyl groups, present in the form of silanols in the case of the commonly used SiO2 dielectric. These findings should therefore open up new opportunities for organic complementary metal-oxide semiconductor (CMOS) circuits, in which both p-type and n-type behaviours are harnessed.

2,191 citations

Journal ArticleDOI
TL;DR: In this paper, the authors derived the stability requirements on electrode potentials of n-type doped conducting polymers and compared the predictions with experimental data on stability of polymers, and showed that an electrode potential of about 0 to + 0.5 V (SCE) is required for stable polymers.

1,349 citations

Journal ArticleDOI
TL;DR: Analysis of the molecular geometries and energetics in these materials reveals a correlation between electron mobility and substituent-induced arylene core distortion, while Vth and I(off) are generally affected by LUMO ener getics.
Abstract: Structural and electronic criteria for ambient stability in n-type organic materials for organic field-effect transistors (OFETs) are investigated by systematically varying LUMO energetics and molecular substituents of arylene diimide-based materials Six OFETs on n+-Si/SiO2 substrates exhibit OFET response parameters as follows: N,N'-bis(n-octyl)perylene-3,4:9,10-bis(dicarboximide) (PDI-8): mu = 032 cm2 V(-1) s(-1), Vth = 55 V, I(on)/I(off) = 10(5); N,N'-bis(n-octyl)-1,7- and N,N'-bis(n-octyl)-1,6-dibromoperylene-3,4:9,10-bis(dicarboximide) (PDI-8Br2): mu = 3 x 10(-5) cm2 V(-1) s(-1), Vth = 62 V, I(on)/I(off) = 10(3); N,N'-bis(n-octyl)-1,6,7,12-tetrachloroperylene-3,4:9,10-bis(dicarboximide) (PDI-8Cl4): mu = 4 x 10(-3) cm2 V(-1) (s-1), Vth = 37 V, I(on)/I(off) = 10(4); N,N'-bis(n-octyl)-2-cyanonaphthalene-1,4,5,8-bis(dicarboximide) (NDI-8CN): mu = 47 x 10(-3) cm2 V(-1) s(-1), Vth = 28, I(on)/I(off) = 10(5); N,N'-bis(n-octyl)-1,7- and N,N'-bis(n-octyl)-1,6-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI-8CN2): mu = 013 cm2 V(-1) s(-1), Vth = -14 V, I(on)/I(off) = 10(3); and N,N'-bis(n-octyl)-2,6-dicyanonaphthalene-1,4,5,8-bis(dicarboximide) (NDI-8CN2): mu = 015 cm2 V(-1) s(-1), Vth = -37 V, I(on)/I(off) = 10(2) Analysis of the molecular geometries and energetics in these materials reveals a correlation between electron mobility and substituent-induced arylene core distortion, while Vth and I(off) are generally affected by LUMO energetics Our findings also indicate that resistance to ambient charge carrier trapping observed in films of N-(n-octyl)arylene diimides occurs at a molecular reduction potential more positive than approximately -01 V (vs SCE) OFET threshold voltage shifts between vacuum and ambient atmosphere operation suggest that, at E(red1) -01 V, the trap density increase is negligible OFETs fabricated with the present n-type materials having E(red1) > -01 V operate at conventional gate biases with minimal hysteresis in air This reduction potential corresponds to an overpotential for the reaction of the charge carriers with O2 of approximately 06 V N,N'-1H,1H-Perfluorobutyl derivatives of the perylene-based semiconductors were also synthesized and used to fabricate OFETs, resulting in air-stable devices for all fluorocarbon-substituted materials, despite generally having E(red1) < -01 V This behavior is consistent with a fluorocarbon-based O2 barrier mechanism OFET cycling measurements in air for dicyanated vs fluorinated materials demonstrate that energetic stabilization of the charge carriers results in greater device longevity in comparison to the OFET degradation observed in air-stable semiconductors with fluorocarbon barriers

976 citations