Perylene Bisimide as a Promising Zinc Oxide Surface Modifier

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Perylene Bisimide as a Promising Zinc Oxide Surface Modifier: Enhanced Interfacial Combination for Highly Efficient Inverted Polymer Solar Cells Li Nian, Wenqiang Zhang, Siping Wu, Leiqiang Qin, Linlin Liu, Zengqi Xie, Hong-Bin Wu, and Yuguang Ma ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.5b07759 • Publication Date (Web): 09 Nov 2015 Downloaded from http://pubs.acs.org on November 13, 2015

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ACS Applied Materials & Interfaces

Perylene Bisimide as a Promising Zinc Oxide Surface Modifier: Enhanced Interfacial Combination for Highly Efficient Inverted Polymer Solar Cells Li Nian, Wenqiang Zhang, Siping Wu, Leiqiang Qin, Linlin Liu, Zengqi Xie,* Hongbin Wu and Yuguang Ma Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China. KEYWORDS: perylene bisimide, zinc oxide modifier, inverted organic photovoltaics, highly efficient, interfacial combination

ABSTRACT: We report the application of a perylene bisimide (PBI-H) as zinc oxide (ZnO) surface modifier to afford an organic-inorganic co-interlayer for highly efficient inverted organic photovoltaics (i-OPV). By thermal annealing, N-Zn chemical bond formed between PBI-H and ZnO, inducing close organic-inorganic combination. In addition, this co-interlayer shows decreased work function, increased electron transportation and conductivity, which are benefits for the cathode to enhance charge extraction efficiency and decrease recombination losses. As a result a highly efficient i-OPV was achieved with a power conversion efficiency (PCE) of 9.43% based on this co-interlayer with PTB7:PC71BM as the active layer, which shows over 35% enhancement compared to that of the device without PBI-H layer. Moreover, this co-interlayer

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was widely applicable for i-OPVs based on various material systems, such as P3HT:PC61BM and PTB7-Th:PC71BM, resulting in PCE as high as 4.78% and 10.31% respectively.

INTRODUCTION Perylene bisimides (PBIs) are a class of archetype n-type organic semiconductors possessing the characteristic properties like high electron affinity and electron mobility as well as tunable electronic energy levels, which have been extensively investigated in the applications of organic photonic, electronic and photovoltaic devices.1-7 Recently, PBI derivatives were emerged to be used as cathode interlayer materials in solution processed organic photovoltaics (OPVs) either through controlling the solvent selective solubility or through formation of totally insoluble cross-linked films.8-11 Hains et al firstly reported the chemically cross-linkable perylene bisimide as n-type interfacial material for inverted OPVs (i-OPVs), the counterpart to the conventional OPVs (c-OPVs), using the cross-linked insoluble films of either itself or its blends with some conjugated polymers as the indium tin oxide (ITO) modifier.9 Such insoluble films were also achieved by us through in situ electrochemical polymerization reaction of multiple carbazole functionalized PBIs, and the improved device performance of i-OPVs was demonstrated.10 Li et al reported water-/ alcohol-soluble PBI derivatives applied as cathode interlayer for c-OPVs, which shows the much desired thickness-insensitive property owing to its self-assembly behavior and excellent electron mobility.11 Most recently, PBI was applied by us as photo sensitizer to achieve photoconductive cathode interlayer by doping it into the matrix of zinc oxide (ZnO), resulting in highly efficient i-OPVs.12 Although the original mechanism for the interlayer electronic process is still ambiguous till now, PBI derivatives show great potential due to the variety of molecule structures as well as the controllable supramolecular structures.13, 14


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ZnO is a classical cathode interlayer material to modify ITO electrode for the construction of i-OPVs, owing to its easy solution procession, relatively high electron mobility, proper energy levels and high transparency across the whole visible spectral range.15-17 While the easily formed surface defects of ZnO during the fabrication process may trap electrons seriously for one hand, and the pure inorganic surface is another penalty for the unpreferred contact with organic materials, which may render large series resistance (Rs) and lead to weak electronic coupling with the active layer and severe back charge recombination.18-21 An effective approach to solve these problems is to modify the ZnO surface with a self-assembled monolayer (SAM) of organic molecules like fullerene derivatives.22-25 Jen's group systematically investigated fullerene-based SAMs modified ZnO as cathode interlayer in OPVs and proved their multiple functions, such as passivating surface charge traps, tuning the energy level offset and making up the upper organic layer morphology.26-29 Till now the reported surface modifiers for ZnO were mostly based on acidic anchoring groups, such as phosphonic acid and carboxylic acid groups, which have shown to potentially degrade and etch the ZnO layer.30 Using polyelectrolytes to modify ZnO is an alternative approach to renovate the surface of ZnO. Heeger's group demonstrated that the power conversion efficiency (PCE) was increased over 25% for small molecule organic solar cells by incorporating polyethylenimine ethoxylated (PEIE) atop of ZnO.31 Woo et al also showed significantly improved device performance of i-OPVs using polyethylenimine (PEI) to modify the surface of ZnO.32 These fascinating results show a bright future of modifying ZnO surface with suitable organic materials to achieve co-interlayers for highly efficient i-OPVs, and more improvement by applying new organic material system as the modifier is expected. In this work, we will demonstrate the application of a perylene bisimide (PBI-H) as ZnO surface modifier to afford an organic-inorganic co-interlayer (ZnO/PBI-H), between which the


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N-Zn chemical bond is formed inducing close organic-inorganic combination that facilitating charge transportation through the co-interlayer. In addition, this co-interlayer shows decreased work function, increased electron transportation and conductivity, which are benefits for the cathode to enhance charge extraction efficiency and decrease recombination losses. An i-OPV using ZnO/PBI-H as the cathode interlayer and PTB7:PC71BM as the active layer affords a very high PCE of 9.43%, which shows over 35% enhancement compared to that of the device without PBI-H layer. Moreover, this co-interlayer was widely applicable for various active materials and the highest PCE was achieved to be 10.31% using PTB7-Th:PC71BM as the active layer. RESULTS AND DISCUSSION The chemical structure of PBI-H is shown in Chart 1, which possesses two N-H groups at the tips of the molecule inducing the formation of one-dimensional nanofibers through multiple intermolecular hydrogen bonds.33 Sol-gel derived ZnO films on quartz or ITO substrates were prepared according to the previous reports.34 The PBI-H layers were coated onto the ZnO layer by spin-coating method from 1mg/ml PBI-H solution in anhydrous tetrahydrofuran (THF). The average thickness of this PBI-H thin layer was determined to be ~10 nm by surface profiler (the thickness of PBI-H was calculated by excluding the thickness of ZnO in ZnO/PBI-H film). We found that the initial color of PBI-H on ZnO was light blue, but the color was changed to light red after thermal treatment (>100℃). As comparison, we also fabricated the PBI-H films on different substrates like quartz, glass and ITO and then the thermal treatment was performed as well, but no obvious change of the color was found at high temperatures. Based on above observations, we proposed that PBI-H molecules might form chemical bond of N-Zn with ZnO during the thermal treatment process according to the recent report.35 To confirm the existence of this N-Zn chemical bond, we prepared the hybrid of PBI-H and ZnO for the X-ray photoelectron


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spectroscopy (XPS) measurement, using both individual components as the references. The results are given in Figure S1. Both signals of N 1s and Zn 2p of the hybrid show obvious shifts compared to the references, which clearly indicates the interaction between ZnO and PBI-H through N-Zn bond (see SI for details). It is noteworthy that the N-Zn chemical bond induces close organic-inorganic combination, which is beneficial to the electron transportation through this interlayer in devices that will be discussed in next section.

O O O

O

HN

NH

O

O O O

PBI-H

Chart 1. Chemical structure of PBI-H. To understand the effect of thermal annealing on the evolution of the morphological properties of PBI-H films on the substrates of ITO/ZnO, the films were treated under different temperatures and then subjected for atomic force microscope (AFM) measurements (Figure 1 and Figure S2). As shown in Figure 1a, rodlike PBI-H aggregates formed readily on ZnO layer with relatively large surface roughness (root mean square roughness (RMS) of 6.986nm); however, the surface morphology changed dramatically after thermal annealing (Figure 1b-d). In detail, after the rodlike aggregates of PBI-H on ZnO were annealed at 120℃ for 5min, the coverage density of the aggregates became sparse and the size of the aggregates became smaller (Figure 1b); while after annealed at 150℃ or 200℃ for 5min, the nanorod aggregates disappeared totally and much flat surface with nano-sized particles formed. The RMS for the 150℃ annealed sample is 1.470nm and that for the 200℃ annealed sample is 1.238nm, which are quite similar to the surface of ZnO film (Figure S2). The average thickness of the 150℃ annealed PBI-H film on


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ZnO was determined to be ~8 nm by surface profiler, which indicates that the PBI-H layer may cover the ZnO substrate well to form a uniform thin film. The small decrease in the thickness of PBI-H from 10 nm (as cast) to 8 nm (annealed at 150℃) could be understood in terms of the more compact film formed during the thermal annealing process. For comparison, we also investigated the morphology of the PBI-H on ITO substrate treated at different temperatures, but no obvious morphological evolution was observed even the annealing temperature was up to 200℃ as shown in Figure S2. The thermal-induced morphological change of PBI-H aggregates on ZnO surface, contrasting to the unchanged morphology on ITO, clearly indicates the unique interaction between PBI-H molecules and ZnO, which corresponds well to the observations of color change as discussed above.

Figure 1. AFM images of ZnO/PBI-H films; (a) as-cast and annealed at (b) 120℃, (c) 150℃, (d) 200℃. The scan size is 5μm × 5μm for all images. Since PBI-H molecules may chemically bound to ZnO surface and thus increase the combination between ZnO and PBI-H, it is reasonable to use ZnO/PBI-H as a co-interlayer in organic devices. Here, we fabricated i-OPVs with the device configuration of ITO/ ZnO (40nm)/ PBI-H (0 or 10nm)/ PTB7:PC71BM (90nm)/ MoO3 (10nm)/ Al (100nm). The current density-


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voltage (J-V) characteristics of the inverted cells under AM 1.5G irradiation at 1000W/m2 and in the dark are shown in Figure 2a and 2b respectively. The extracted device performance metrics, including Rs and shunt resistance (Rsh), are summarized in Table 1. The device with ZnO/PBI-H (as-cast) as the cathode co-interlayer gave a PCE of 7.99% with an open circuit voltage (Voc) of 0.74V, a short circuit current density (Jsc) of 15.76mA cm-2 and a fill factor (FF) of 68.51%, which is higher than the value obtained from the device with ZnO as the solo interlayer (PCE=6.98%, Voc=0.73V, Jsc=14.80 mA cm-2 and FF=64.64%). Moreover, the PCE of the ZnO/PBI-H based device was further increased to 9.43% after the co-interlayer was thermal treated at 150℃, mainly due to the enhanced inorganic-organic interfacial combination. As shown in Figure 2 and Table 1, the increased PCE is attributed to that all the device parameters were improved significantly compared to the ZnO based control device (Voc from 0.73V to 0.75V, Jsc from 14.80 mA cm-2 to16.84 mA cm-2, FF from 64.64% to 74.66%). The Rsh variation of the devices (0.43 kΩ cm2 for ZnO based device to 2.25 kΩ cm2 for ZnO/PBI-H based device) may be the major reason for the slightly increased Voc. As for the Rsh improvement, it may be attributed to the reduced leakage current as shown in Figure 2b. The increased Jsc could be understood by the reduced Rs (from 6.24 Ω cm2 to 2.71Ω cm2) and enhanced Rsh (from 0.43 kΩ cm2 to 2.25 kΩ cm2) of the ZnO/PBI-H (150℃ annealed) based device, which correlates to the improved interfacial combination between ZnO and PBI-H (by NZn chemical bonding) and the enhanced interfacial contact (from organic-inorganic contact for ZnO/ active layer to organic-organic contact for PBI-H/ active layer). The EQE spectra of iOPVs in Figure 2c support the increase in Jsc and the calculated Jsc obtained by integration of the EQE curves showed less than 2% mismatch compared with Jsc values obtained from the J-V curves. The improved morphology of PBI-H aggregates by thermal annealing promotes electron


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extraction from the active layer, and the close contact between PBI-H and ZnO facilitates the electron transportation that avoids the electron accumulation near the interlayer, and thus gives a high FF. In experiment, we also noted that if the ZnO/PBI-H co-interlayer was annealed at relatively higher temperature, e.g. 200℃, the device showed quite poor performance, which might be attributed to the unsuitable work function and reduced electron transportation as discussed below. (b)

0

ZnO ZnO/PBI-H as-cast o ZnO/PBI-H 120 C o ZnO/PBI-H 150 C o ZnO/PBI-H 200 C

Current Density (mA/cm )

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80

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0 300

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700

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Figure 2. (a) The current density-voltage (J-V) characteristics of the inverted devices with different interlayers under 1000W/m2 AM 1.5G illumination. (b) J-V curves in dark. (c) EQE curves. The device structure is ITO/ interlayer/ PTB7:PC71BM (90nm)/ MoO3 (10nm)/ Al


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(100nm), in which interlayer indicates ZnO (40nm) or ZnO (40nm)/ PBI-H(10nm) with different annealing temperatures. Table 1. Device performance based on PTB7:PC71BM under 1000W/m2 AM illumination with various interlayers. a) Cathode interlayer

Voc (V)

Jsc (mA/cm2)

PCE (%) b)

FF (%)

Rsc)

Rshd)

(Ω cm2)

(Ω cm2)

ZnO

0.73±0.005

14.55±0.25

64.40±0.24

6.77±0.19 (6.98)

6.24

428.26

ZnO/PBI-H (as-cast)

0.74±0.005

15.59±0.17

68.23±0.28

7.73±0.21 (7.99)

4.62

689.18

ZnO/PBI-H (120℃)

0.74±0.005

15.77±0.21

70.78±0.21

8.22±0.14 (8.39)

4.58

874.34

ZnO/PBI-H (150℃)

0.75±0.005

16.65±0.19

74.47±0.19

9.27±0.12 (9.43)

2.71

2251.02

ZnO/PBI-H (200℃)

0.69±0.005

15.41±0.26

58.30±0.31

6.02±0.25 (6.34)

7.99

216.35

a)

Statistic data achieved from 15 independent devices. b) The maxima PCEs in the brackets.

c)

Series resistance Rs and

d)

shunt resistance Rsh were defined from the J-V curves of the best

devices at V=Voc and V=0, respectively. As the work function of the interlayer has great influence on device performance, ultraviolet photoelectron spectroscopy (UPS) was used to test the electronic properties of ZnO, ZnO/PBI-H (annealed at 150℃ and 200℃) on ITO substrates as shown in Figure 3. ITO/ZnO film possesses a typical WF of 4.31eV; while ITO/ZnO/PBI-H (150℃ annealed) shows reduced WF with decreased value of 0.3eV. The low WF value of ZnO/PBI-H modified ITO allows to form ohmic contact with PC71BM acceptor and to increase the built-in field, which is a benefit to the enhanced charge extraction efficiency and the decreased recombination losses. However, the ZnO/PBI-H (200℃ annealed) showed higher WF compared with ZnO, which was unfavourable for the built-in field and charge extraction. The unsuitable WF also consisted with the low Voc for the device based on ZnO/PBI-H (200℃ annealed) interlayer.


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(a)

Normalized Intensity (a.u.)

ITO ITO/ZnO o ITO/ZnO/PBI-H 150 C o ITO/ZnO/PBI-H 200 C

0.31eV

3.0

3.5

0.13eV

4.0

4.5

5.0

Kinetic energy (eV)

Figure 3. (a) UPS spectra of bare ITO, ITO/ ZnO (40nm), and ITO/ ZnO (40nm)/ PBI-H (10nm) (annealed at 150℃) and ITO/ ZnO (40nm)/ PBI-H (10nm) (annealed at 200℃). (b) Energy level diagram of the components of the inverted device based on ZnO or ZnO/PBI-H (annealed at 150℃ and 200℃) interlayer under flat band condition (open-circuit voltage).

In our very recent report in the PBI-H doping ZnO system, the PBI-H doped ZnO film showed highly photoconductivity under 1000W/m2 AM 1.5G illumination due to the electron transfer from PBI-H to ZnO.12 Similar to the PBI-H doping ZnO system, the ZnO/PBI-H film (150℃ annealed) also showed much higher conductivity compared with the ZnO film under 1000W/m2 AM 1.5G illumination as shown in Figure 4, which is favorable for suppressing charge recombination and facilitating electron extraction for OPVs.12 60

ZnO under illumination o ZnO/PBI-H 150 C under illumination

50

Current (mA)

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Al

40

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Figure 4. I-V curves of the devices for ITO/ ZnO (40nm)/ Al and ITO/ ZnO (40nm)/ PBI-H (10nm) (annealed at 150℃)/ Al under 1000W/m2 AM 1.5G illumination. To investigate the electron transport properties of the different interlayers, electron-only devices with an Al/ interlayer/ PTB7:PC71BM/ Ca/ Al configuration were fabricated (Figure 5a). The electron-current densities were increased significant for the as-cast, 120℃, 150℃ annealed ZnO/PBI-H based devices compared with ZnO based device. In particular, the electron-current density of the device based on 150℃ annealed ZnO/PBI-H interlayer was almost one order of magnitude higher than the device based on ZnO interlayer, indicating much better electron transportation. This result is consist with the higher FF value for the devices based on 150℃ annealed ZnO/PBI-H cathode interlayer (Figure 2a) and the enhanced dark current under forward bias in the dark J-V curves (Figure 2b). However, the electron-current density of 200℃ annealed device decreased almost two orders of magnitude compared with 150℃ annealed device, indicating much decreased electron transportation, which would be one reason for the poor device performance. To find out the reason for the improved electron transportation caused by PBI-H modification, we fabricated another type of electron only devices: Al/ ZnO or PBI-H/ Ca/ Al to test the electron mobility of ZnO and PBI-H respectively (Figure 5b). The electron mobility of PBI-H was almost one order of magnitude lower than ZnO (7.14×10-5 cm2 V-1 s-1 for PBI-H and 6.82×10-4 cm2 V-1 s-1 for ZnO), which was opposite to the much better electron transportation of ZnO/PBI-H/PTB7:PC71BM compared with ZnO/PTB7:PC71BM (Figure 5a). These distinct results indicated that the enhanced interfacial contact (from organic-inorganic contact for ZnO/ PC71BM to organic-organic contact for PBI-H/ PC71BM) should be the reason for the improved


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electron transportation for ZnO/PBI-H based device compared with ZnO based device, rather than the different electron mobility of PBI-H and ZnO. (a)

(b)

4

100 ZnO PBI-H

2

(A /m)

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ZnO ZnO/PBI-H as-cast

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60

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2.4

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Effective Voltage (V)

Figure 5. (a) J-V curves of the electron-only devices with ZnO and ZnO/PBI-H with different annealing temperatures as the interlayers based on PTB7:PC71BM blend. Electron-only device configuration: Al/ ZnO (40nm)/ PBI-H (0 or 10nm)/ PTB7:PC71BM (90nm)/ Ca/ Al. (b) J1/2~V characteristics of electron-only devices with configuration of Al/ ZnO (100 nm) or PBI-H (100 nm)/ Ca/ Al.

In order to test the widely applicable of the PBI-H modified ZnO cathode interlayer, we also fabricated i-OPVs using P3HT:PC61BM and PTB7-Th:PC71BM as the active layers. The current density-voltage (J-V) characteristics are shown in Figure 6 and the extracted device performance metrics are summarized in Table 2. The devices using ZnO/PBI-H (150℃) as cathode interlayer showed high PCEmax of 4.78% (based on P3HT:PC61BM) and PCEmax of 10.31% (based on PTB7-Th:PC71BM), both of which are much higher than that of the device with the same active layer but using ZnO cathode interlayer (PCEmax=3.51% based on P3HT:PC61BM and PCEmax=8.33% based on PTB7-Th:PC71BM).


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Figure 6. J-V characteristics of the i-OPVs with ZnO or ZnO/PBI-H 150℃ as cathode interlayer under 1000W/m2 AM 1.5G illumination. The device configurations are ITO/ ZnO/active layer/MoO3/Al or ITO/ ZnO/PBI-H (annealed at 150℃)/ active layer/ MoO3/ Al. The active layer is (a) P3HT:PC61BM (200nm) (b) PTB7-Th:PC71BM (90nm).

Table 2. Device performance based on different active layer under 1000W/m2 AM illumination with ZnO or ZnO/PBI-H 150℃ as cathode interlayer. a) Device configuration

Voc (V)

Jsc (mA/cm2)

FF (%)

PCE (%) b)

ITO/ZnO/P3HT:PC61BM/ MoO3/Al

0.61±0.005

9.30±0.23

60.18±0.19

3.13±0.28 (3.51)

ITO/ZnO/PBI-H/P3HT:PC61BM/ MoO3/Al

0.63±0.005

10.76±0.21

68.85±0.21

4.48±0.24 (4.78)

ITO/ZnO/PTB7-Th:PC71BM/ MoO3/Al

0.79±0.005

15.40±0.17

67.55±0.22

8.11±0.17 (8.33)

ITO/ZnO/PBI-H/ PTB7-Th:PC71BM/MoO3/Al

0.80±0.005

17.03±0.18

74.68±0.18

10.11±0.15 (10.31)

a)

Statistic data achieved from 10 independent devices. b) The maxima PCEs in the brackets.

CONCLUSIONS In conclusion, we have successfully demonstrated enhanced PCEs in i-OPVs through using a cointerlayer of ZnO/PBI-H. This co-interlayer showed decreased work function and increased electron transportation and conductivity, compared to the solo ZnO interlayer. By thermal


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annealing, the co-interlayer showed enhanced interfacial combination by forming N-Zn chemical bond, which facilitated the electron extraction from the active layer in device and resulted in significantly enhanced PCE up to 9.43% for PTB7:PC71BM based device. In addition, this cointerlayer was widely applicable for various material systems based i-OPVs, such as P3HT:PC61BM (PCEmax=4.78%) and PTB7-Th:PC71BM (PCEmax=10.31%). We highlight that combining ZnO and a n-type small molecule like PBI-H as cathode interlayer can achieve very high efficiency in i-OPVs, by means of proper design of molecule. We also anticipate that our findings will catalyze the development of new interlayer materials and may improve the efficiency of other organic electronic devices like perovskite solar cells.

ASSOCIATED CONTENT Supporting Information. Detailed experimental procedures, XPS, AFM images, water contact angle images, UV-visible absorption and UPS of ZnO, PBI-H and ZnO:PBI-H thin films. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author * E-mail: [email protected]. Fax: +86-20-87110606; Tel: +86-20-22237035. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT


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We thank the financial supports from the Natural Science Foundation of China (51373054, 51303057, 51473052, 21334002), National Basic Research Program of China (973 Program) (2014CB643504, 2013CB834705), Fundamental Research Funds for the Central Universities (2015ZZ003) and Introduced Innovative R&D Team of Guangdong (201101C0105067115). REFERENCES (1) Würthner, F. Perylene Bisimide Dyes as Versatile Building Blocks for Functional Supramolecular Architectures. Chem. Commun. 2004, 40, 1564-1579. (2) Schmidt-Mende, L.; Fechtenkötter, A.; Müllen, K.; Moons, E.; Friend, R. H.; MacKenzie, J. D. Self-Organized Discotic Liquid Crystals for High-Efficiency Organic Photovoltaics. Science 2001, 293, 1119-1122. (3) Li, C.; Wonneberger, H. Perylene Imides for Organic Photovoltaics: Yesterday, Today, and Tomorrow. Adv. Mater. 2012, 24, 613-636. (4) Zhong, Y.; Trinh, M. T.; Chen, R.; Wang, W.; Khlyabich, P. P.; Kumar, B.; Xu, Q.; Nam, C.- Y.; Sfeir, M. Y.; Black, C.; Steigerwald, M. L.; Loo, Y.- L.; Xiao, S.; Ng, F.; Zhu, X.- Y.; Nuckolls, C. Efficient Organic Solar Cells with Helical Perylene Diimide Electron Acceptors. J. Am. Chem. Soc. 2014, 136, 15215-15221. (5) Zhao, Y.; Guo, Y.; Liu, Y. 25th Anniversary Article: Recent Advances in n-Type and Ambipolar Organic Field-Effect Transistors. Adv. Mater. 2013, 25, 5372-5391. (6) Lin, Y.; Wang, Y.; Wang, J.; Hou, J.; Li, Y.; Zhu, D.; Zhan, X. A Star-Shaped Perylene Diimide Electron Acceptor for High-Performance Organic Solar Cells. Adv. Mater. 2014, 26, 5137-5142. (7) Troeger, A.; Ledendecker, M.; Margraf, J. T.; Sgobba, V.; Guldi, D. M.; Vieweg, B. F.; Spiecker, E.; Suraru, S.- L.; Würthner, F. p-Doped Multiwall Carbon Nanotube/Perylene


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Coordination Polymers: Syntheses, Crystal Structures and Properties. Cryst. Growth Des. 2012, 12, 4580-4587.

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Perylene Bisimide as a Promising Zinc Oxide Surface Modifier

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