Intermolecular Electronic Transitions and ... - ACS Publications

Subscriber access provided by TULANE UNIVERSITY

C: Physical Processes in Nanomaterials and Nanostructures

Graphene-Organic Two-Dimensional Charge Transfer Complexes: InterMolecular Electronic Transitions and Broadband near Infrared Photoresponse Menghua Cui, Yuzheng Guo, Yiming Zhu, Haining Liu, Wen Wen, Juanxia Wu, Linxiu Cheng, Qingdao Zeng, and Liming Xie J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.8b01408 • Publication Date (Web): 15 Mar 2018 Downloaded from http://pubs.acs.org on March 16, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Graphene-Organic

Two-Dimensional

Charge

Transfer Complexes: Inter-Molecular Electronic Transitions

and

Broadband

Near

Infrared

Photoresponse †‡§

Menghua Cui , , , Yuzheng Guo

‖,*

†

†

†§

†

, Yiming Zhu , Haining Liu , Wen Wen , , Juanxia Wu , Linxiu

Cheng†, Qingdao Zeng† and Liming Xie†,§,* †

CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for

Excellence in Na-noscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China ‡

Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, P. R.

China §

University of Chinese Academy of Sciences, Beijing 100049, P. R. China

‖

College of Engineering, Swansea University, Swansea, SA1 8EN, United Kingdom

ACS Paragon Plus Environment

1

The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 18

ABSTRACT: Charge transfer (CT) complex with unique inter-molecule electronic transitions has attracted broad interest and holds great potentials in optoelectronic applications. Here, we report a new family of two-dimensional graphene-organic molecule CT complexes. Density functional theory (DFT) calculation has revealed low-energy CT bands in the near infrared (NIR) region up to 2000 nm for graphene-TCNQ (tetracyanoquinodimethane), graphene-F4TCNQ (2,3,5,6-Tetrafluoro-tetracyanoquinodimethane)

and

graphene-TCOQ

(tetrachloro-o-

benzoquinone) complexes. Raman and electrical measurements have confirmed a partial charge transfer between graphene and the molecules at the ground state. CT excitations have been calculated by DFT and verified by optoelectronic measurements. The graphene-organic CT complexes have shown a broadband photoresponse from visible to NIR range, attributing to the inter-molecule electronic transitions. Further, the photo-responsivity (up to 103 A/W) suggests a high photoelectrical gain arising from the photogating effect at the graphene/molecule interface. At last, the photoresponse property of the graphene-organic CT complexes can be tuned by electrical gating of graphene.


2

Page 3 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Introduction Since the discovery of tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) charge transfer (CT) complex in 19731, CT complex consisting of electron donors and electron acceptors has attracted great interest due to its unique electrical2-4, optical3-8 and magnetic9,10 properties. Owing to the molecular orbital overlapping and hybridization, CT complex has unique low-energy inter-molecule electronic transitions down to near infrared (NIR) region11-14. The inter-molecule electronic transition accomplishes high efficient charge separation and hence has great potentials in high-efficiency solar cells15,16 and high-performance photodetectors14. Graphene17, a layer of honeycomb sp2 carbon atoms with delocalized π electron system, is a promising candidate for CT complexes with atomic thickness18. Due to the continuous electronic states in graphene, graphene-based CT complexes can have broadband inter-molecule CT transitions down to infrared (IR) range. Further, the charge separation at the two-dimensional interface can make graphene-based CT complexes favorable for high-gain photodetection, in which the separated charges in graphene can circulate millions of circles before recombination with the opposite charges in the molecules due to the extremely high carrier mobility in graphene19-25 and slow charge recombination rate between graphene and the molecules. In the past years, graphene-organic molecule interactions26, such as doping27-32, excited state charge/energy transfer8,33-35, have been intensively investigated. However, inter-molecule electronic transition between graphene and organic molecules, i.e., CT transition, has not been reported. Here we have calculated electronic structure of graphene-organic CT complexes, a new kind of two-dimensional CT complex consisting of a conductive conjugated atomic layer and a layer of molecules. The investigated molecules include tetracyanoquinodimethane (TCNQ),


3


2,3,5,6-tetrafluoro-tetracyanoquinodimethane

(F4TCNQ)

and

Page 4 of 18

tetrachloro-o-benzoquinone

(TCOQ). Taking graphene-TCNQ CT complex as an example, density functional theory (DFT) calculation has revealed inter-molecule CT transitions covering a spectrum range from 500 to 2400 nm. Field-effect transistors (FETs) of graphene-TCNQ CT complex have been fabricated and showed ultrahigh NIR photoresponse from visible to 2000 nm with a peak responsivity higher than 2000 A/W. In addition, the photoresponse can be tuned by electrical gating of graphene. Methods DFT calculation. All electronic and optical properties are cal-culated with plane-wave pseudopotential package CASTEP. It has been confirmed by previous calculation that local density functionals could describe the electronic structure of graphene quite accurately. PBEstyle GGA functional was used for all the calculation. A graphene supercell of 12 Å × 12 Å was constructed with different molecule absorbed on just one side. The van der Waals interaction was included in the empirical TS scheme. The structure was relaxed by BFGS scheme with a residual force smaller than 0.01 eV/Å. A standard ultrasoft pseuopotential was used with a cut off energy of 450 eV. Only Γ point was used for geometry optimization while a 3×3 Monkhorst-Pack grid was used for electronic and optical properties calculation. Materials. TCNQ (PN#1427366, 98%), F4TCNQ (PN#2157887, 97%) and TCOQ (PN#1309782, 97%) were purchased from Sigma Aldrich. Characterization. AFM (Dimension 3100, Veeco, America) was performed with tapping mode. STM (Nanoscope IIIa, Bruker, Germany) images were conducted at Iset =491.3 pA, Vbais


4

Page 5 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


=559.1 mV. Raman spectrum was measured on a home-built setup with 532 nm continuous laser and the laser power was below 0.2 mW/µm2. Device fabrication. Graphene flakes were obtained by me-chanical exfoliation of Kish graphite (Covalent Material Corp., Japan) on a silicon wafer with 300 nm SiO2 layer. Copper TEM grid with 10 µm spacing was used as a shadow mask. 10 nm Ti and 50 nm Au were deposited for the electrodes. After evapora-tion, the electrodes and back silicon gate were wired to a home-made chip carrier. The device was then immersed in TCNQ, F4TCNQ or TCOQ saturated solution in acetone for adsorption and dried in N2 blow before photocurrent measurements. Photoresponse measurement. The photocurrent measure-ment system was home-built with a pulsed laser (EXR-4, NKT, Denmark, output wavelength from 540 to 2400 nm). A series of bandpass filters from 700 nm to 2000 nm (FKB-VIS-40, FKB-IR-10, FB1750-500 and FB2000500, Thorlabs Inc., USA) and neu-tral density filters (GCC-301041, GCC-301061 and GCC301071, Daheng Optics, China; NENIR10A, NENIR20A and NENIR30A, Thorlabs Inc., USA) were used to select the output wavelength and output power. The light spot diameter was about 2 mm. The laser power under each condition was measured by a pow-er meter (PM100A, Thorlabs Inc., USA) with different sensors suitable for the various wavelengths. The photoresponse rate was measured by an amperemeter (DMM7510, Tektronix Inc., USA) with light chopping up to 10 kHz (MC2000B, Thorlabs Inc., USA). Results & Discussion Figure 1 shows calculated electronic structure of graphene-TCNQ CT complex. The Mulliken charge analysis shows that there is 0.18 e transferred from graphene to TCNQ per molecule. The


5


Page 6 of 18

optimized structure is shown in Figure 1a. The partial density of states (PDOS) is shown in Figure 1b. The Fermi level in graphene is shifted down by 0.2 eV from the Dirac point, resulting from the electron transfer from graphene to TCNQ at the ground state. Absorption spectrum is calculated for graphene-TCNQ complex, showing three new peaks at longer wavelengths (~600, 900 and 1750 nm, Figure 1c). The three peaks correspond to electronic transitions from the highest occupied molecule orbital (HOMO) to three unoccupied orbitals. The HOMO is mainly contributed by graphene (96%) while the three unoccupied orbitals are contributed by both graphene (48% to 64%) and TCNQ (52% to 36%) (Figure 1c insets). This suggests that the three electronic transitions involve partial electron transfer from graphene to TCNQ, i.e., intermolecule CT transitions. Similar results have been observed for graphene-F4TCNQ and graphene-TCOQ CT complexes (Figure S1 and S2). In brief, graphene-F4TCNQ shows CT bands around 900, 1900 nm and graphene-TCOQ shows CT bands around 900 nm.


6

Page 7 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. Calculated electronic structure of graphene-TCNQ change transfer (CT) complex. (a) CT complex structure, (b) partial density of states (PDOS) and (c) calculated absorption spectrum of graphene-TCNQ CT complex. Insets in panel c are the highest occupied molecule orbital (HOMO) and unoccupied orbitals (corresponding to the CT bands). The numbers are the orbital contributions of graphene or TCNQ. Graphene was exfoliated on SiO2/Si substrates and then soaked in TCNQ solution for molecule adsorption. Scanning tunneling microscopic (STM) imaging confirmed TCNQ adsorption on graphite surface (Figure 2a inset). Raman spectroscopic characterization showed


7


Page 8 of 18

an upshift of the G band from 1584 to 1589 cm-1 (Figure 2b), indicating a p-doping effect. This is consistent with the DFT calculation result of electron transfer from graphene to TCNQ at the ground state. This p-doping effect of TCNQ on graphene was also observed from field-effect transport measurements (Figure 2c,d), in which the minimum conductance point (the Dirac point) shifted to a more positive gate voltage after TCNQ adsorption.

Figure 2. Characterization of graphene-TCNQ CT complex. (a) A typical atomic force microscopic (AFM) image of graphene. The inset is a scanning tunneling microscopic (STM) image of adsorbed TCNQ molecules on graphite. (b) Raman spectra, (c) Source-drain current (Ids) to gate-source voltage (Vgs) curves and (d) Ids to source-drain voltage (Vds) curves of graphene before and after TCNQ adsorption.


8

Page 9 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Further, graphene-organic CT complexes were put under NIR light illumination for photoresponse measurements (Figure 3a). For the graphene-TCNQ device shown in Figure 2c, a photocurrent of µA level was observed under 1000 nm illumination with powers from 0.35 nW to 0.19 µW (Figure 3b). Since graphene was gated at p-type region (Vgs was -40 V), the positive photocurrent indicates hole injection into graphene at light illumination. That is consistent with DFT calculation result, i.e., the CT bands associate electron transfer from graphene to TCNQ (Figure 1c).

Figure 3. Photoresponse of graphene-TCNQ charge transfer (CT) complex. (a) Scheme of photocurrent measurement setup. (b) photoresponse (base current was subtracted), (c) extracted photocurrent and responsivity of graphene-TCNQ complex measured at 1000 nm with different


9


Page 10 of 18

powers. The inset in (b) is a typical optical image of graphene-TCNQ device. (d,e) photoresponse of graphene-TCNQ complex at different chopping frequencies.

The photoresponsivity of graphene-TCNQ complex at low light illumination was as high as ~2000 A/W (Figure 3c, red data), indicating an ultrahigh photoelectrical gain. Similarly, high responsivity up to 120 A/W (at 1000 nm) and 240 A/W (at 1000 nm) were observed for graphene-F4TCNQ and graphene-TCOQ complexes, respectively (Figure S3 and S4). The gain is attributed to the photogating effect20,36,37, i.e., the holes in graphene circulate many times in the device before recombination with electrons in TCNQ due to the extremely high carrier mobility in graphene and slow charge recombination rate between graphene and TCNQ. As light power increased, the photocurrent increased but not linearly (Figure 3c). This is a saturation effect which is commonly observed in graphene20,22 and MoS238,39 based photogating photodetectors. The photoresponse speed was also measured by light chopping. As the light chopping frequency increased to 10 kHz, the responsivity only dropped about 30% (Figure 3d,e). This suggests that the electron-hole recombination rate in graphene-TCNQ is still faster than 0.1 ms. Further, wavelength-dependent photoresponse of graphene-organic CT complex was measured (Figure 4). Graphene-TCNQ complex has a broad photoresponse from visible to 2000 nm. While graphene-F4TCNQ and graphene-TCOQ have photoresponse from visible to 1200 nm. The wavelength-dependent responsivity (in A/W) matches well with the calculated absorption spectrum below 1200 nm. For graphene-TCNQ complex, at longer wavelength from 1400 to 2000 nm, the measured photoresponse is lower than the calculated absorption, in which the explanation is not clear and it needs further investigation.


10

Page 11 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. Wavelength-dependent photoresponse of (a) graphene-TCNQ, (b) graphene-F4TCNQ and (c) graphene-TCOQ charge transfer (CT) complexes. The light power at different wavelengths is shown in Figure S5.

The Fermi level of graphene can be tuned by the gate voltage17,40. At negative gate voltages, graphene is p-doped with major carriers of holes. In a quantitatively picture, considering graphene Dirac point at -4.6 eV and the lowest unoccupied molecule orbital (LUMO) of TCNQ, F4TCNQ, TCOQ at -4.6, -5.2 and -4.5 eV, respectively, the charge (electron) transfer transition is allowed from graphene to LUMO of the molecules (Figure 5a left panel). However, when the Fermi level of graphene rises to a n-doped region at strong positive gate voltages, the Fermi level of graphene is higher than the LUMO of the molecules. As a result, the charge (electron) transfer transition from graphene to organic molecule is blocked (Figure 5a right panel).


11


(a)

Graphene at Positive Vgs

Graphene at Negative Vgs

+

+ Molecule EF

Vgs

Molecule

EF

Vgs

×

LUMO

LUMO HOMO

HOMO

-

-

0

0 -80 -40

0

40

Vgs (V)

80

G-F4TCNQ

1

700nm 850nm 900nm 1000nm 1100nm

-80 -40

0

40

(d) Relative responsivity

(c)

700 nm 1000 nm 1200 nm 1600 nm 2000 nm

G-TCNQ

1

Relative responsivity

(b) Relative responsivity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 18

80

Vgs (V)

1

0

G-TCOQ

700 nm 800 nm 900 nm 1000 nm 1100 nm

-80 -40 0

40 80

Vgs (V)

Figure 5. (a) Charge-transfer (CT) transitions in graphene-organic CT complex at different gate voltages. Gate-dependent photoresponse of (b) graphene-TCNQ, (c) graphene-F4TCNQ and (d) graphene-TCOQ CT complexes.

In experiments, strong photoresponse was observed at negative gate voltages while no photoresponse was observed at gate voltages higher than 40 V for all graphene-TCNQ, graphene-F4TCNQ and graphene-TCOQ complexes (Figure 5b,c,d). This is consistent with the quantitative picture shown in Figure 5a. Therefore, the external electrical gating can be used to tune electronic excitations in graphene-organic CT complexes. Conclusions In conclusion, we have calculated the electronic structure of graphene-organic CT complexes: a new type of CT complexes with broadband NIR CT transitions. Taking advantages of the high


12

Page 13 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


carrier mobility of graphene and the photogating effect at graphene/molecule interface, high photoresponsivity (up to 2000 A/W) and high speed (10 kHz) photodetection have been measured from graphene-organic CT complexes. This provides a new type of tailorable NIR optical materials with potential applications in highly responsive photodetectors. ASSOCIATED CONTENT Supporting Information. Calculated absorption spectra of graphene-F4TCNQ and graphene-TCOQ CT complexes, characterization and photoresponse of graphene-F4TCNQ CT complex, characterization and photoresponse of graphene-TCOQ CT complex, laser power at different wavelength used in Figure 4, and full author lists for Reference 3 and 39. AUTHOR INFORMATION Corresponding Author *[email protected], Tel.: +8610-82545722. *[email protected], Tel.: +44-1792602994. Author Contributions M. C. did device fabrication and photoresponse experiments, organized the data and supporting information. Y. G. did the DFT calculation. Y. Z., W. W. and J. W. participated in the device fabrication and photoresponse experiments. H. L. did the Raman and AFM characterization. L. C. and Q. Z. did the STM imaging. L. X. designed the project. All authors contributed the manuscript.


13


Page 14 of 18

Notes The authors declare no competing financial interests. ACKNOWLEDGMENT L.X. acknowledges support from the Key Research Program of Frontier Sciences of CAS (QYZDB-SSW-SYS031), NSFC (21673058) and Beijing Talents Fund (2015000021223ZK17). REFERENCES (1) Grobman, W. D.; Pollak, R. A.; Eastman, D. E.; Maas, E. T.; Scott, B. A. Valence Electronic Structure and Charge Transfer in Tetrathiofulvalinium Tetracyanoquinodimethane (TTF-TCNQ) from Photoemission Spectroscopy. Phys. Rev. Lett. 1974, 32, 534-537. (2) Goetz, K. P.; Vermeulen, D.; Payne, M. E.; Kloc, C.; McNeil, L. E.; Jurchescu, O. D. Charge-Transfer Complexes: New Perspectives on an Old Class of Compounds. J. Mater. Chem. C 2014, 2, 3065-3076. (3) Goetz, K. P.; Tsutsumi, J. y.; Pookpanratana, S.; Chen, J.; Corbin, N. S.; Behera, R. K.; Coropceanu, V.; Richter, C. A.; Hacker, C. A.; Hasegawa, T.; et al. Polymorphism in the 1:1 Charge-Transfer Complex DBTTF–TCNQ and Its Effects on Optical and Electronic Properties. Adv. Electron Mater. 2016, 2, 1600203-n/a. (4) Abdou, M. S. A.; Orfino, F. P.; Son, Y.; Holdcroft, S. Interaction of Oxygen with Conjugated Polymers: Charge Transfer Complex Formation with Poly(3-Alkylthiophenes). J. Am. Chem. Soc. 1997, 119, 4518-4524. (5) Manna, A. K.; Pati, S. K. Tuning the Electronic Structure of Graphene by Molecular Charge Transfer: A Computational Study. Chem-Asian J. 2009, 4, 855-860. (6) Rabie, U. M. A Review on Electronic Spectral Studies of Charge Transfer Complexes. J. Mol. Struct. 2013, 1034, 393-403. (7) Lei, Y. L.; Liao, L. S.; Lee, S. T. Selective Growth of Dual-Color-Emitting Heterogeneous Microdumbbells Composed of Organic Charge-Transfer Complexes. J. Am. Chem. Soc. 2013, 135, 3744-3747.


14

Page 15 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(8) Lei, Y.-L.; Jin, Y.; Zhou, D.-Y.; Gu, W.; Shi, X.-B.; Liao, L.-S.; Lee, S.-T. White-Light Emitting Microtubes of Mixed Organic Charge-Transfer Complexes. Adv. Mater. 2012, 24, 5345-5351. (9) Shil, S.; Paul, S.; Misra, A. Charge-Transfer-Induced Magnetism in Mixed-Stack Complexes. J. Phys. Chem. C 2013, 117, 2016-2023. (10) Enoki, T.; Miyazaki, A. Magnetic Ttf-Based Charge-Transfer Complexes. Chem. Rev. 2004, 104, 5449-5478. (11) Friedrich, H. B.; Person, W. B. Infrared Spectra of Charge‐Transfer Complexes. Vi. Theory. J. Chem. Phys. 1966, 44, 2161-2170. (12) Wu, S. P.; Kang, Y.; Liu, T. L.; Jin, Z. H.; Jiang, N.; Lu, Z. H. Formation of ChargeTransfer-Complex in Organic:Metal Oxides Systems. Appl. Phys. Lett. 2013, 102, 163304. (13) Cameron, L. A.; Ziller, J. W.; Heyduk, A. F. Near-Ir Absorbing Donor-Acceptor Ligandto-Ligand Charge-Transfer Complexes of Nickel(Ii). Chem. Sci. 2016, 7, 1807-1814. (14) Ng, T.-W.; Lo, M.-F.; Fung, M.-K.; Zhang, W.-J.; Lee, C.-S. Charge-Transfer Complexes and Their Role in Exciplex Emission and near-Infrared Photovoltaics. Adv. Mater. 2014, 26, 5569-5574. (15) Deibel, C.; Strobel, T.; Dyakonov, V. Role of the Charge Transfer State in Organic Donor– Acceptor Solar Cells. Adv. Mater. 2010, 22, 4097-4111. (16) Vandewal, K.; Gadisa, A.; Oosterbaan, W. D.; Bertho, S.; Banishoeib, F.; Van Severen, I.; Lutsen, L.; Cleij, T. J.; Vanderzande, D.; Manca, J. V. The Relation between Open-Circuit Voltage and the Onset of Photocurrent Generation by Charge-Transfer Absorption in Polymer : Fullerene Bulk Heterojunction Solar Cells. Adv. Funct. Mater. 2008, 18, 2064-2070. (17) Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A. Electric Field Effect in Atomically Thin Carbon Films. Sci. 2004, 306, 666-669. (18) Muruganathan, M.; Sun, J.; Imamura, T.; Mizuta, H. Electrically Tunable Van Der Waals Interaction in Graphene–Molecule Complex. Nano Lett. 2015, 15, 8176-8180. (19) Vicarelli, L.; Vitiello, M. S.; Coquillat, D.; Lombardo, A.; Ferrari, A. C.; Knap, W.; Polini, M.; Pellegrini, V.; Tredicucci, A. Graphene Field-Effect Transistors as Room-Temperature Terahertz Detectors. Nat. Mater. 2012, 11, 865.


15


Page 16 of 18

(20) Konstantatos, G.; Badioli, M.; Gaudreau, L.; Osmond, J.; Bernechea, M.; de Arquer, F. P. G.; Gatti, F.; Koppens, F. H. L. Hybrid Graphene–Quantum Dot Phototransistors with Ultrahigh Gain. Nat. Nanotech. 2012, 7, 363. (21) Tan, W.-C.; Shih, W.-H.; Chen, Y. F. A Highly Sensitive Graphene-Organic Hybrid Photodetector with a Piezoelectric Substrate. Adv. Funct. Mater. 2014, 24, 6818-6825. (22) Liu, C.-H.; Chang, Y.-C.; Norris, T. B.; Zhong, Z. Graphene Photodetectors with UltraBroadband and High Responsivity at Room Temperature. Nat. Nanotech. 2014, 9, 273. (23) Seong Jun, K.; Wooseok, S.; Sungho, K.; Min, A. K.; Sung, M.; Sun Sook, L.; Jongsun, L.; Ki-Seok, A. Tunable Functionalization of Graphene Nanosheets for Graphene-Organic Hybrid Photodetectors. Nanotech. 2016, 27, 075709. (24) Lee, Y.; Yu, S. H.; Jeon, J.; Kim, H.; Lee, J. Y.; Kim, H.; Ahn, J.-H.; Hwang, E.; Cho, J. H. Hybrid Structures of Organic Dye and Graphene for Ultrahigh Gain Photodetectors. Carbon 2015, 88, 165-172. (25) Fang, H.; Hu, W. Photogating in Low Dimensional Photodetectors. Adv. Sci. 2017, 4, 1700323-n/a. (26) Das, B.; Voggu, R.; Rout, C. S.; Rao, C. N. R. Changes in the Electronic Structure and Properties of Graphene Induced by Molecular Charge-Transfer. Chem. Commun. 2008, 51555157. (27) Sun, J. T.; Lu, Y. H.; Chen, W.; Feng, Y. P.; Wee, A. T. S. Linear Tuning of Charge Carriers in Graphene by Organic Molecules and Charge-Transfer Complexes. Phys. Rev. B 2010, 81, 155403. (28) Koch, N.; Duhm, S.; Rabe, J. P.; Vollmer, A.; Johnson, R. L. Optimized Hole Injection with Strong Electron Acceptors at Organic-Metal Interfaces. Phys. Rev. Lett. 2005, 95, 237601. (29) Hu, T.; Gerber, I. C. Theoretical Study of the Interaction of Electron Donor and Acceptor Molecules with Graphene. J. Phys. Chem. C 2013, 117, 2411-2420. (30) Samuels, A. J.; Carey, J. D. Molecular Doping and Band-Gap Opening of Bilayer Graphene. ACS Nano 2013, 7, 2790-2799. (31) Du, A.; Ng, Y. H.; Bell, N. J.; Zhu, Z.; Amal, R.; Smith, S. C. Hybrid Graphene/Titania Nanocomposite: Interface Charge Transfer, Hole Doping, and Sensitization for Visible Light Response. J. Phys. Chem. Lett. 2011, 2, 894-899.


16

Page 17 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(32) Zhou, X.; He, S.; Brown, K. A.; Mendez-Arroyo, J.; Boey, F.; Mirkin, C. A. Locally Altering the Electronic Properties of Graphene by Nanoscopically Doping It with Rhodamine 6G. Nano Lett. 2013, 13, 1616-1621. (33) Stein, T.; Kronik, L.; Baer, R. Reliable Prediction of Charge Transfer Excitations in Molecular Complexes Using Time-Dependent Density Functional Theory. J. Am. Chem. Soc. 2009, 131, 2818-2820. (34) Xie, L.; Ling, X.; Fang, Y.; Zhang, J.; Liu, Z. Graphene as a Substrate to Suppress Fluorescence in Resonance Raman Spectroscopy. J. Am. Chem. Soc. 2009, 131, 9890-9891. (35) Ling, X.; Xie, L.; Fang, Y.; Xu, H.; Zhang, H.; Kong, J.; Dresselhaus, M. S.; Zhang, J.; Liu, Z. Can Graphene Be Used as a Substrate for Raman Enhancement? Nano Lett. 2010, 10, 553-561. (36) Koppens, F. H. L.; Mueller, T.; Avouris, P.; Ferrari, A. C.; Vitiello, M. S.; Polini, M. Photodetectors Based on Graphene, Other Two-Dimensional Materials and Hybrid Systems. Nat. Nanotech. 2014, 9, 780. (37) Sun, Z.; Liu, Z.; Li, J.; Tai, G.-a.; Lau, S.-P.; Yan, F. Infrared Photodetectors Based on CVD-Grown Graphene and PbS Quantum Dots with Ultrahigh Responsivity. Adv. Mater. 2012, 24, 5878-5883. (38) Lopez-Sanchez, O.; Lembke, D.; Kayci, M.; Radenovic, A.; Kis, A. Ultrasensitive Photodetectors Based on Monolayer MoS2. Nat. Nanotech. 2013, 8, 497. (39) Chen, C.; Qiao, H.; Lin, S.; Man Luk, C.; Liu, Y.; Xu, Z.; Song, J.; Xue, Y.; Li, D.; Yuan, J.; et al. Highly Responsive MoS2 Photodetectors Enhanced by Graphene Quantum Dots. Sci. Rep. 2015, 5, 11830. (40) Dharmendar, R.; Leonard, F. R.; Gary, D. C.; Sanjay, K. B. Graphene Field-Effect Transistors. J. Phys. D: Appl. Phys. 2011, 44, 313001.


17


Page 18 of 18

Table of contents graphic


18

Intermolecular Electronic Transitions and ... - ACS Publications

Recommend Documents