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Optical Materials Express

Optical Materials Express

  • Editor: David J. Hagan
  • Vol. 2, Iss. 6 — Jun. 1, 2012
  • pp: 856–863
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TPD doped polystyrene as charge transporter in DiPBI sensitized photorefractive composites

Thomas Schemme, Evgenij Travkin, Katharina Ditte, Wei Jiang, Zhaohui Wang, and Cornelia Denz  »View Author Affiliations


Optical Materials Express, Vol. 2, Issue 6, pp. 856-863 (2012)
http://dx.doi.org/10.1364/OME.2.000856


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Abstract

We incorporate a mixture of polystyrene (PS) and the highly conductive N, N′-diphenyl-N, N′-bis(3-methylphenyl)-[1, 1′-biphenyl]-4, 4′-diamine (TPD) as charge transporting agent into a photorefractive composite, wherein the liquid crystal 4-cyano-4-n-pentylbiphenyl (5CB) is the electro-optical unit and the perylene bisimide dimer DiPBI acts as sensitizing component. Investigation of the photocurrent reveals a strong enhancement of the photoconductivity. Compared to composites, wherein poly-n-vinylcarbazole (PVK) is the charge transporting agent, the internal photocurrent efficiency is enhanced 11 times. This dramatic improvement is attributed to an increase of charge generation and transport and it allows for a reduction of the applied electric field to get a photoconductivity that is comparable to PVK comprising composites.

© 2012 OSA

1. Introduction

In recent years, large research efforts have been made to find fast and cheap materials that can be used in holographic applications. Typically, photorefractive inorganic crystals like iron doped lithium niobate are used in these applications [1

1. C. Denz, K.-O. Müller, T. Heimann, and T. Tschudi, “Volume holographic storage demonstrator based on phase-coded multiplexing,” IEEE J. Sel. Top. Quantum Electron. 4, 832–839 (1998). [CrossRef]

, 2

2. K. Buse, “Light-induced charge transport processes in photorefractive crystals II: Materials,” Appl. Phys. B: Lasers Opt. 64, 391–407 (1997). [CrossRef]

]. But beside their cost intensive and complex growth processes, their photorefractive performance is rather slow and they can only be manufactured in small dimensions. Photorefractive composites are one type of materials, which feature the possibility to replace inorganic crystals in holographic applications [3

3. W. Moerner, A. Grunnet-Jepsen, and C. Thompson, “Photorefractive Polymers,” Annu. Rev. Mater. Sci. 27, 585–623 (1997). [CrossRef]

]. Especially if large area devices, fast response times, or easy and cheap fabrication are needed, photorefractive composites outmatch their inorganic counterparts. Due to these properties, photorefractive composites are ideal candidates to be employed as optical beam couplers, fast storage devices [4

4. O. Ostroverkhova and W. Moerner, “Organic photorefractives: Mechanisms, materials, and applications,” Chem. Rev. 104, 3267–3314 (2004). [CrossRef] [PubMed]

], holographic 3D displays [5

5. J. Thomas, R. A. Norwood, and N. Peyghambarian, “Non-linear optical polymers for photorefractive applications,” J. Mater. Chem. 19, 7476–7489 (2009). [CrossRef]

, 6

6. P.-A. Blanche, A. Bablumian, R. Voorakaranam, C. Christenson, W. Lin, T. Gu, D. Flores, P. Wang, W.-Y. Hsieh, M. Kathaperumal, B. Rachwal, O. Siddiqui, J. Thomas, R. A. Norwood, M. Yamamoto, and N. Peyghambarian, “Holographic three-dimensional telepresence using large-area photorefractive polymer,” Nature 468, 80–83 (2010). [CrossRef] [PubMed]

], and tomographs for living tissue [7

7. M. Salvador, J. Prauzner, S. Köber, K. Meerholz, J. J. Turek, K. Jeong, and D. D. Nolte, “Three-dimensional holographic imaging of living tissue using a highly sensitive photorefractive polymer device,” Opt. Express 17, 11834–11849 (2009). [CrossRef] [PubMed]

].

The photorefractive (PR) effect describes a reversible refractive index change, caused by inhomogeneous illumination of the material [8

8. P. Günter and J.-P. Huignard, Photorefractive Materials and their Applications 1: Basic Effects (Springer, 2006). [CrossRef]

]. This refractive index change has two underlying processes: photoconductivity and the electro-optic effect. When a photorefractive composite is illuminated with a light pattern, absorbing sensitizer molecules are excited in regions with high light intensity. Under the influence of an applied external electric field, these excitons are separated, and the mobile holes move through the (polymeric) hole transporter to the regions with low light intensity, while the electrons remain immobile in the excited sensitizer molecules. In the dark regions, holes can be trapped and hence the redistributed charges lead to the formation of a space-charge field. Nonlinear optical units, also called chromophores, provide the electro-optic effect and therefore can translate the space-charge field into the desired refractive index change [9

9. W. E. Moerner and S. M. Silence, “Polymeric photorefractive materials,” Chem. Rev. 94, 127–155 (1994). [CrossRef]

].

One challenge in the optimization process of PR composites is the reduction of the external electric field to achieve a refractive index change [10

10. S. Köber, M. Salvador, and K. Meerholz, “Organic Photorefractive Materials and Applications,” Adv. Mater. 23, 4725–4763 (2011). [CrossRef]

]. Currently, several tens to hundred V μm−1 have to be applied. This challenge can be addressed in different ways. One possibility is to find improved nonlinear optical units, that can generate the refractive index change more efficient and do not need large electric fields for preorientation. Another possibility is the optimization of the photoconductivity. As the photoconductivity is a combined phenomenon of charge generation and charge mobility [11

11. D. V. Steenwinckel, E. Hendrickx, and A. Persoons, “Dynamics and steady-state properties of photorefractive poly(N-vinylcarbazole)-based composites sensitized with (2,4,7-trinitro-9-fluorenylidene)malononitrile in a 0–3 wt % range,” J. Chem. Phys. 114, 9557–9564 (2001). [CrossRef]

], optimization of both effects can improve it. An enhanced charge generation will probably lead to a stronger space-charge field with reduced build-up time. Also an improvement of the mobility will lead to a faster redistribution of the charges and therefore a more rapid generation of the space-charge field. Recently, we achieved dramatically improved charge generation when we replaced C60 by the perylene bisimide dimer DiPBI as sensitizer in the well-known composite of the electro-optic liquid crystal 4-cyano-4-n-pentylbiphenyl (5CB) and the conductive polymer poly-n-vinylcarbazole (PVK) (5CB:PVK:C60) [12

12. J. Zhang and K. Singer, “Homogeneous photorefractive polymer/nematogen composite,” Appl. Phys. Lett. 72, 2948–2950 (1998). [CrossRef]

14

14. K. Ditte, W. Jiang, T. Schemme, C. Denz, and Z. Wang, “Innovative Sensitizer DiPBI Outperforms PCBM,” Adv. Mater. 24, 2104–2108 (2012). [CrossRef] [PubMed]

]. In this paper, we demonstrate an approach to further improve the photoconductivity by employing the highly conductive N, N′-diphenyl-N, N′-bis(3-methylphenyl)-[1, 1′-biphenyl]-4, 4′-diamine (TPD) embedded in polystyrene (PS) as charge transporting agent [15

15. G. B. Jung, M. Yoshida, T. Mutai, R. Fujimura, S. Ashihara, T. Shimura, K. Araki, and K. Kuroda, “High-speed TPD-based Photorefractive Polymer Composites,” Sen’i Gakkaishi 60, 193–197 (2004). [CrossRef] [PubMed]

, 16

16. S. R. Mohan and M. Joshi, “Field dependence of hole mobility in TPD-doped polystyrene,” Solid State Commun. 139, 181–185 (2006). [CrossRef]

] in our composites. TPD based charge transport has been studied for several years. Due to its high mobility, it is often used as a functional group in charge transporting polymers [6

6. P.-A. Blanche, A. Bablumian, R. Voorakaranam, C. Christenson, W. Lin, T. Gu, D. Flores, P. Wang, W.-Y. Hsieh, M. Kathaperumal, B. Rachwal, O. Siddiqui, J. Thomas, R. A. Norwood, M. Yamamoto, and N. Peyghambarian, “Holographic three-dimensional telepresence using large-area photorefractive polymer,” Nature 468, 80–83 (2010). [CrossRef] [PubMed]

, 17

17. K. Ogino, T. Nomura, T. Shichi, S.-H. Park, H. Sato, T. Aoyama, and T. Wada, “Synthesis of Polymers Having Tetraphenyldiaminobiphenyl Units for a Host Polymer of Photorefractive Composite,” Chem. Mater. 9, 2768–2775 (1997). [CrossRef]

, 18

18. H. J. Bolink, V. V. Krasnikov, P. H. J. Kouwer, and G. Hadziioannou, “A Novel Polyaryl Ether Based Photorefractive Composite,” Chem. Mater. 10, 3951–3957 (1998). [CrossRef]

]. Additionally, charge transport in pure films of TPD and TPD doped polystyrene (PS:TPD) has been studied [16

16. S. R. Mohan and M. Joshi, “Field dependence of hole mobility in TPD-doped polystyrene,” Solid State Commun. 139, 181–185 (2006). [CrossRef]

, 19

19. E. Hendrickx, B. Kippelen, S. Thayumanavan, S. R. Marder, A. Persoons, and N. Peyghambarian, “High photogeneration efficiency of charge-transfer complexes formed between low ionization potential arylamines and C60,” J. Chem. Phys. 112, 9557–9561 (2000). [CrossRef]

]. Also the formation of charge transfer complexes in PS:TPD with C60 has been observed [19

19. E. Hendrickx, B. Kippelen, S. Thayumanavan, S. R. Marder, A. Persoons, and N. Peyghambarian, “High photogeneration efficiency of charge-transfer complexes formed between low ionization potential arylamines and C60,” J. Chem. Phys. 112, 9557–9561 (2000). [CrossRef]

].

2. Sample preparation and experimental techniques

To analyze the influence of PS:TPD on the photoconductivity, we apply our well characterized composition 5CB:PVK:DiPBI with a weight ratio of 40.18:59.80:0.02 wt% as reference system, and replace PVK by PS:TPD in a weight ratio of 80.00:20.00 wt%. If PVK is replaced by pristine TPD or higher doped PS, composites tend to unwanted crystallization and the composite loses its transparency [20

20. F. Khan, A.-M. Hor, and P. R. Sundararajan, “Morphological reasoning for the enhanced charge carrier mobility of a hole transport molecule in polystyrene,” Pure Appl. Chem. 76, 1509–1520 (2004). [CrossRef]

]. Because of the electro-optic as well as the plasticizing properties of 5CB, we have chosen this material as a nonlinear optical unit. As an advantage, no further plasticizing component is needed to adjust the glass transition temperature Tg of the composites. Referring to the publication of Zhang and Singer [12

12. J. Zhang and K. Singer, “Homogeneous photorefractive polymer/nematogen composite,” Appl. Phys. Lett. 72, 2948–2950 (1998). [CrossRef]

], Tg for the PVK comprising samples is about 40 °C. Khan et al. reported Tg ≈ 70 °C for PS:TPD at a ratio of 80.00:20.00 wt% [20

20. F. Khan, A.-M. Hor, and P. R. Sundararajan, “Morphological reasoning for the enhanced charge carrier mobility of a hole transport molecule in polystyrene,” Pure Appl. Chem. 76, 1509–1520 (2004). [CrossRef]

]. Assuming that 5CB further lowers the glass transition temperature, we estimate Tg for the PS:TPD comprising samples to be close to room temperature. The energy levels depicted in Table 1 illustrate that the differences between PVK and TPD are rather low and both should be suitable to build an efficient charge transporting complex with DiPBI. The difference between the HOMO levels of DiPBI and TPD is even larger than between DiPBI and PVK. This enhanced energetic difference can contribute to an improved charge separation between both components and therefore both can build a more efficient charge transfer complex than DiPBI and PVK. Because of the lower HOMO level of 5CB compared to the charge transporting agents, trapping of holes by 5CB molecules would be unlikely. Polystyrene works as an inert host material for TPD [20

20. F. Khan, A.-M. Hor, and P. R. Sundararajan, “Morphological reasoning for the enhanced charge carrier mobility of a hole transport molecule in polystyrene,” Pure Appl. Chem. 76, 1509–1520 (2004). [CrossRef]

], thus trapping by PS is not expected and all traps are considered as intrinsic and caused by the conformation of the components. Higher amounts of PS may lead to an increased spatial disorder and thus broadening of the density of states and more intrinsic traps, because TPD molecules are no longer surrounded by other TPD molecules, and the conductivity of PS:TPD is reduced. At the chosen ratio of PS and TPD, we assume that PS does not incorporate large amounts of traps into the composite.

Table 1. Energy Levels of the Components 5CB [21], PVK [22], TPD [23], and DiPBI [24]

table-icon
View This Table

Fig. 1 Absorption spectra of samples containing PS:TPD or PVK as hole transporter.

The characterization of the photoelectric properties of the samples is carried out by measurements of the photocurrent Iph with a Keithley 6485 picoammeter under homogeneous illumination by an expanded laser beam. The hole electrode area a = 39 mm2 of the samples is irradiated with an intensity of W = 16 mWcm−2 at a wavelength of 532 nm, and an applied external electric field Eext. During the measurement procedure, the dark current Idark as well as the current under homogeneous illumination I are investigated. The photocurrent Iph is given by Iph = IIdark. Then the photoconductivity is calculated by
σph=IphaEext.
(1)
To eliminate the influence of small differences in the absorption properties of the samples, we calculate the internal photocurrent efficiency ϕint [27

27. T. K. Däubler, R. Bittner, K. Meerholz, V. Cimrová, and D. Neher, “Charge carrier photogeneration, trapping, and space-charge field formation in PVK-based photorefractive materials,” Phys. Rev. B 61, 13515–13527 (2000). [CrossRef]

] with
ϕint=σphEexthνeαdW,
(2)
where h is Planck’s constant, ν the frequency of light, e the elementary charge, α the absorption coefficient of the particular sample and d the sample thickness.

The photorefractive qualities are investigated for different applied electric fields by the well-known two-beam coupling technique [28

28. P. Yeh, “Two-Wave Mixing in Nonlinear Media,” IEEE J. Quantum. Electron. 25, 97–132 (1989). [CrossRef]

]. We illuminate the sample with two interfering laser beams, each with an intensity of W1,2 = 8 mWcm−2. The sample normal is tilted with respect to beam 1 by 40° and beam 2 by 60°, resulting in a grating spacing of 2 μm, if a refractive index of n = 1.7 is assumed. The energy transfer between both p-polarized beams is given by the gain coefficient Γ, calculated with
Γ=1L[ln(γb)ln(1+bγ)],
(3)
where b is the intensity ratio between the beams in front of the sample and L the optical path length inside the sample. The gain γ is measured after propagation through the sample via a photo diode and is described by the expression γ = W1(W2 > 0)/W1(W2 = 0).

3. Photoconductive and photorefractive properties

The photocurrent measurements reveal stronger dark- and photocurrents for the PS:TPD comprising samples. These results can be directly transferred to the photo- and dark conductivities, as their relation is linear. At an applied field of 30 V μm−1, the dark conductivities are σd,PVK = (0.013±0.001) pScm−1 and σd,PS:TPD = (0.036 ± 0.002) pScm−1, and the corresponding photoconductivities σph,PVK = (0.009 ± 0.001) pScm−1 and σph,PS:TPD = (0.112 ± 0.004) pScm−1. Therefore, the dark conductivity in the PS:TPD comprising composites is about three times larger than in composites incorporating PVK as hole transporter. In contrast, the photoconductivity is 12 times larger for PS:TPD than for PVK containing samples. The internal photocurrent efficiencies, calculated by Eq. (2), in dependence on the applied electric field are depicted in Fig. 2. It can be observed, that both compositions provide an explicit increase of ϕint with rising Eext. For the PS:TPD composition, an enhancement of the internal photocurrent efficiency by a factor 11 at an electric field of 30 V μm−1 is observed. The values at this field are (5.0 ± 1.0) × 10−6 and (5.5 ± 1.1) × 10−5 for PVK and PS:TPD comprising samples, respectively. This enhancement is attributed to an improved charge separation between DiPBI and TPD molecules, and a much larger mobility of the holes in TPD, caused by a reduced trap concentration compared to PVK. Further aspects, such as the higher mobility in pristine TPD relative to pristine PVK [17

17. K. Ogino, T. Nomura, T. Shichi, S.-H. Park, H. Sato, T. Aoyama, and T. Wada, “Synthesis of Polymers Having Tetraphenyldiaminobiphenyl Units for a Host Polymer of Photorefractive Composite,” Chem. Mater. 9, 2768–2775 (1997). [CrossRef]

], or the change in the ionization potential between PVK and TPD [19

19. E. Hendrickx, B. Kippelen, S. Thayumanavan, S. R. Marder, A. Persoons, and N. Peyghambarian, “High photogeneration efficiency of charge-transfer complexes formed between low ionization potential arylamines and C60,” J. Chem. Phys. 112, 9557–9561 (2000). [CrossRef]

] also contribute to the enhancements. Due to the high mobility, charges are transported more effective through the composite and therefore the enhanced photoconductivity can be explained. The change in the ionization potential crucially enhances the charge separation between sensitizer and charge transporting agent and hence, also contributes strongly to the enhanced photoconductivity. The increased dark conductivity hints to a decreased trap concentration in PS:TPD. Regarding to these aspects of the PS:TPD system, it allows for effective charge generation and transport at low applied electric fields.

Fig. 2 Comparison of the internal photocurrent efficiency of samples containing PS:TPD or PVK as hole transporter in dependence on the applied electric field.

Fig. 3 Dependence of the two-beam coupling gain coefficient on the applied electric field for PS:TPD and PVK containing samples.

The gain coefficient of the two-beam coupling experiment strongly depends on the strength of the space-charge field and on the phase shift of the refractive index grating. For highest gain coefficients, strong space-charge fields and a 90° phase shift of the refractive index grating with respect to the incident light pattern are desired. Therefore, the low gain of the samples can be caused by weak space-charge fields or too small phase shifts. The lower performance of the PS:TPD samples is explained by a too low trap concentration in the samples. For a strong and fast PR performance not only the mobility has to be high, but also there has to be enough trapping of redistributed charges for a strong space-charge field. High dark currents and therefore low trapping inevitably lead to low photorefractivity because of weak space-charge fields. Whereas TPD is known to provide a high mobility, PS is an inert material in PS:TPD. As reported earlier, charge transport operates well in the chosen ratio of PS and TPD [16

16. S. R. Mohan and M. Joshi, “Field dependence of hole mobility in TPD-doped polystyrene,” Solid State Commun. 139, 181–185 (2006). [CrossRef]

]. Therefore, an increased trapping rate compared to PVK resulting in a reduced phase shift of the refractive index grating during the two-beam coupling experiment is not expected. Therefore we do not estimate the phase shift to be smaller than 90° and therefore, the small gain coefficients in the PS:TPD samples are attributed to the small amplitude of the space-charge field. To further improve PR properties of the composites, the contrast between photo- and dark conductivity has to be enlarged. In the presented composition, this may be realized by a reduction of the TPD content or doping with a further component to incorporate more traps. Due to these steps, the mobility of the holes will be lowered and so the photoconductivity, resulting in the need of higher applied fields. Therefore, a trade-off between the photo- and dark conductivity has to be found.

When the overall performance in a photorefractive material is low, it is difficult to observe a fast photorefractive response. Due to the small amplitudes of the two-beam coupling, we could not determine the time constants of the two-beam coupling, and therefore, could not prove the assumption that PS:TPD would help in the space charge build-up and increase photorefractive speed.

4. Conclusion

We characterize the photorefractive composite 5CB:PS:TPD:DiPBI by absorption spectroscopy, photocurrent measurements, and two-beam coupling and compare the results with the reference composition 5CB:PVK:DiPBI. Incisive improvements of the photoconductive properties in PS:TPD comprising composites are observed. These enhancements are attributed to the outstanding properties of the charge generator DiPBI and the hole transporting PS:TPD system, namely: broad absorption, highly effective charge generation and transport. Consequently, the choice of a TPD based charge transporting agent in combination with DiPBI as sensitizer is a promising approach for photorefractive composites operating at reduced electric fields. The two-beam coupling gain coefficient in TPD comprising samples remains lower than in the PVK comprising composites. We attribute the smaller PR performance to the lower trap concentration in PS:TPD and so to the reduced space-charge field.

Acknowledgments

Financial support by Deutsche Forschungsgemeinschaft within the SFB/Transregio TRR 61 and Open Access Publication Fund of University of Münster is gratefully acknowledged.

References and links

1.

C. Denz, K.-O. Müller, T. Heimann, and T. Tschudi, “Volume holographic storage demonstrator based on phase-coded multiplexing,” IEEE J. Sel. Top. Quantum Electron. 4, 832–839 (1998). [CrossRef]

2.

K. Buse, “Light-induced charge transport processes in photorefractive crystals II: Materials,” Appl. Phys. B: Lasers Opt. 64, 391–407 (1997). [CrossRef]

3.

W. Moerner, A. Grunnet-Jepsen, and C. Thompson, “Photorefractive Polymers,” Annu. Rev. Mater. Sci. 27, 585–623 (1997). [CrossRef]

4.

O. Ostroverkhova and W. Moerner, “Organic photorefractives: Mechanisms, materials, and applications,” Chem. Rev. 104, 3267–3314 (2004). [CrossRef] [PubMed]

5.

J. Thomas, R. A. Norwood, and N. Peyghambarian, “Non-linear optical polymers for photorefractive applications,” J. Mater. Chem. 19, 7476–7489 (2009). [CrossRef]

6.

P.-A. Blanche, A. Bablumian, R. Voorakaranam, C. Christenson, W. Lin, T. Gu, D. Flores, P. Wang, W.-Y. Hsieh, M. Kathaperumal, B. Rachwal, O. Siddiqui, J. Thomas, R. A. Norwood, M. Yamamoto, and N. Peyghambarian, “Holographic three-dimensional telepresence using large-area photorefractive polymer,” Nature 468, 80–83 (2010). [CrossRef] [PubMed]

7.

M. Salvador, J. Prauzner, S. Köber, K. Meerholz, J. J. Turek, K. Jeong, and D. D. Nolte, “Three-dimensional holographic imaging of living tissue using a highly sensitive photorefractive polymer device,” Opt. Express 17, 11834–11849 (2009). [CrossRef] [PubMed]

8.

P. Günter and J.-P. Huignard, Photorefractive Materials and their Applications 1: Basic Effects (Springer, 2006). [CrossRef]

9.

W. E. Moerner and S. M. Silence, “Polymeric photorefractive materials,” Chem. Rev. 94, 127–155 (1994). [CrossRef]

10.

S. Köber, M. Salvador, and K. Meerholz, “Organic Photorefractive Materials and Applications,” Adv. Mater. 23, 4725–4763 (2011). [CrossRef]

11.

D. V. Steenwinckel, E. Hendrickx, and A. Persoons, “Dynamics and steady-state properties of photorefractive poly(N-vinylcarbazole)-based composites sensitized with (2,4,7-trinitro-9-fluorenylidene)malononitrile in a 0–3 wt % range,” J. Chem. Phys. 114, 9557–9564 (2001). [CrossRef]

12.

J. Zhang and K. Singer, “Homogeneous photorefractive polymer/nematogen composite,” Appl. Phys. Lett. 72, 2948–2950 (1998). [CrossRef]

13.

O. Ostroverkhova and K. Singer, “Space-charge dynamics in photorefractive polymers,” J. Appl. Phys. 92, 1727–1743 (2002). [CrossRef]

14.

K. Ditte, W. Jiang, T. Schemme, C. Denz, and Z. Wang, “Innovative Sensitizer DiPBI Outperforms PCBM,” Adv. Mater. 24, 2104–2108 (2012). [CrossRef] [PubMed]

15.

G. B. Jung, M. Yoshida, T. Mutai, R. Fujimura, S. Ashihara, T. Shimura, K. Araki, and K. Kuroda, “High-speed TPD-based Photorefractive Polymer Composites,” Sen’i Gakkaishi 60, 193–197 (2004). [CrossRef] [PubMed]

16.

S. R. Mohan and M. Joshi, “Field dependence of hole mobility in TPD-doped polystyrene,” Solid State Commun. 139, 181–185 (2006). [CrossRef]

17.

K. Ogino, T. Nomura, T. Shichi, S.-H. Park, H. Sato, T. Aoyama, and T. Wada, “Synthesis of Polymers Having Tetraphenyldiaminobiphenyl Units for a Host Polymer of Photorefractive Composite,” Chem. Mater. 9, 2768–2775 (1997). [CrossRef]

18.

H. J. Bolink, V. V. Krasnikov, P. H. J. Kouwer, and G. Hadziioannou, “A Novel Polyaryl Ether Based Photorefractive Composite,” Chem. Mater. 10, 3951–3957 (1998). [CrossRef]

19.

E. Hendrickx, B. Kippelen, S. Thayumanavan, S. R. Marder, A. Persoons, and N. Peyghambarian, “High photogeneration efficiency of charge-transfer complexes formed between low ionization potential arylamines and C60,” J. Chem. Phys. 112, 9557–9561 (2000). [CrossRef]

20.

F. Khan, A.-M. Hor, and P. R. Sundararajan, “Morphological reasoning for the enhanced charge carrier mobility of a hole transport molecule in polystyrene,” Pure Appl. Chem. 76, 1509–1520 (2004). [CrossRef]

21.

A. Grunnet-Jepsen, D. Wright, B. Smith, M. Bratcher, M. DeClue, J. Siegel, and W. Moerner, “Spectroscopic determination of trap density in C-60-sensitized photorefractive polymers,” Chem. Phys. Lett. 291, 553–561 (1998). [CrossRef]

22.

M.-M. Shi, H.-Z. Chen, J.-Z. Sun, J. Ye, and M. Wang, “Excellent ambipolar photoconductivity of PVK film doped with fluoroperylene diimide,” Chem. Phys. Lett. 381, 666–671 (2003). [CrossRef]

23.

J. Morgado, L. Alccer, M. Esteves, N. Pires, and B. Gigante, “New stylbene-based arylamines with dehydroabietic acid methyl ester moieties for organic light-emitting diodes,” Thin Solid Films 515, 7697–7700 (2007). [CrossRef]

24.

A. Lv, S. R. Puniredd, J. Zhang, Z. Li, H. Zhu, W. Jiang, H. Dong, Y. He, L. Jiang, Y. Li, W. Pisula, Q. Meng, W. Hu, and Z. Wang, “High Mobility Air Stable Organic Single Crystal Transistors of a n-Type Diperylene Bisimide,” Adv. Mater. (to be published). [PubMed]

25.

H. Qian, Z. Wang, W. Yue, and D. Zhu, “Exceptional Coupling of Tetrachloroperylene Bisimide: Combination of Ullmann Reaction and C–H Transformation,” J. Am. Chem. Soc. 129, 10664–10665 (2007). [CrossRef] [PubMed]

26.

D. F. Swinehart, “The Beer-Lambert Law,” J. Chem. Educ. 39, 333–335 (1962). [CrossRef]

27.

T. K. Däubler, R. Bittner, K. Meerholz, V. Cimrová, and D. Neher, “Charge carrier photogeneration, trapping, and space-charge field formation in PVK-based photorefractive materials,” Phys. Rev. B 61, 13515–13527 (2000). [CrossRef]

28.

P. Yeh, “Two-Wave Mixing in Nonlinear Media,” IEEE J. Quantum. Electron. 25, 97–132 (1989). [CrossRef]

OCIS Codes
(050.7330) Diffraction and gratings : Volume gratings
(160.4890) Materials : Organic materials
(160.5320) Materials : Photorefractive materials

ToC Category:
Photorefractive Materials

History
Original Manuscript: February 22, 2012
Revised Manuscript: April 20, 2012
Manuscript Accepted: May 3, 2012
Published: May 23, 2012

Citation
Thomas Schemme, Evgenij Travkin, Katharina Ditte, Wei Jiang, Zhaohui Wang, and Cornelia Denz, "TPD doped polystyrene as charge transporter in DiPBI sensitized photorefractive composites," Opt. Mater. Express 2, 856-863 (2012)
http://www.opticsinfobase.org/ome/abstract.cfm?URI=ome-2-6-856


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References

  1. C. Denz, K.-O. Müller, T. Heimann, and T. Tschudi, “Volume holographic storage demonstrator based on phase-coded multiplexing,” IEEE J. Sel. Top. Quantum Electron.4, 832–839 (1998). [CrossRef]
  2. K. Buse, “Light-induced charge transport processes in photorefractive crystals II: Materials,” Appl. Phys. B: Lasers Opt.64, 391–407 (1997). [CrossRef]
  3. W. Moerner, A. Grunnet-Jepsen, and C. Thompson, “Photorefractive Polymers,” Annu. Rev. Mater. Sci.27, 585–623 (1997). [CrossRef]
  4. O. Ostroverkhova and W. Moerner, “Organic photorefractives: Mechanisms, materials, and applications,” Chem. Rev.104, 3267–3314 (2004). [CrossRef] [PubMed]
  5. J. Thomas, R. A. Norwood, and N. Peyghambarian, “Non-linear optical polymers for photorefractive applications,” J. Mater. Chem.19, 7476–7489 (2009). [CrossRef]
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