Low-Temperature and Corrosion-Resistant Gas Diffusion Multibarrier

Subscriber access provided by UNIV OF LOUISIANA

Organic Electronic Devices

Low-Temperature and Corrosion-Resistant Gas Diffusion Multi-Barrier with UV and Heat Rejection Capability – A Strategy to Ensure Reliability of Organic Electronics Jeong Hyun Kwon, Yongmin Jeon, Do-Geun Kim, Seunghun Lee, Sangmin Lee, Taek-Soo Kim, and Kyung Cheol Choi ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b02268 • Publication Date (Web): 12 Apr 2019 Downloaded from http://pubs.acs.org on April 12, 2019

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 21 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

ACS Applied Materials & Interfaces

Low-Temperature and Corrosion-Resistant Gas Diffusion Multi-Barrier with UV and Heat Rejection Capability – A Strategy to Ensure Reliability of Organic Electronics Jeong Hyun Kwon†, Yongmin Jeon‡, Do-Geun Kim†, Seunghun Lee†, Sangmin Lee§, Taek-Soo Kim§ and Kyung Cheol Choi*,‡

Advanced Nano-Surface Department, Korea Institute of Materials Science, Changwon, Gyeongnam 51508, Republic of Korea ‡ School of Electrical Engineering, KAIST, Daejeon 34141, Republic of Korea § Department of Mechanical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea †

* E-mail

: [email protected]

Keywords. Organic electronic devices; UV filter; gas diffusion multibarrier; Dielectric/Metal/Dielectric (DMD); thin film passivation

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

Abstract When placed in an outdoor environment, organic electronic devices (OEDs) can degrade on exposure to moisture, UV light, and heat, owing to the chemical sensitivity and decomposition of the organic materials. Therefore, to protect OEDs from outdoor environments, thin film passivation, which can block harmful elements from reaching organic materials, is required. To meet the demands and trends in encapsulation technologies, in this study, we developed a low-temperature, simple, and effective gas diffusion multibarrier (GDM), which is UV- and heat-reflective as well as corrosion-resistant. The designed UV- and heat-reflective gas diffusion multibarrier (UHGDM) has a multistacked structure in the form of a UV filter/Ag/gas diffusion barrier (GDB)/polymer based on a dielectric/metal/dielectric (DMD) configuration. First, the DMD structure was used as a heat mirror for infrared reflectance. Second, the bottom dielectric layer of the DMD structure was used as the UV filter, and it consisted of a ZnS/LiF multistacked structure with large differences in refractive indexes. Third, a nanolaminate-based GDB barrier with multi-interfacial and defect-decoupling systems, which achieved a water vapor transmission rate of 1.58 × 10−5 g/m2/day at a thickness of 60 nm, was used as the top dielectric layer of the DMD structure. Finally, an inorganic/organic hybrid polymer layer was coated on the DMD structure to provide corrosion-resistance and waterproofing properties. The fabricated UHGDM showed high transparency in the visible region and excellent reflectance in the UV and IR regions, resulting in excellent UV and heat rejection capability in practical UV and heat reflection tests. In addition to optical functionalities, the UHGDM maintained its functionality against harsh environmental conditions due to the GDB/polymer structure. Finally, the feasibility of the UHGDM was demonstrated using organic solar cells through water immersion and shelf lifetime tests.

1. Introduction Organic electronic devices (OEDs), such as organic light-emitting diodes (OLEDs), organic solar cells (OSCs), and organic thin-film transistors, have been actively studied.1–4 Although current OEDs show excellent device efficiency, they have critical environmental reliability issues. In particular, among OEDs, when OSCs are placed in an outdoor environment and exposed to sunlight, which is composed of ultraviolet (UV), infrared (IR), visible light, and reactive gases, they are easily degraded due to their sensitivity to environmental factors, resulting in decreased efficiency and lifetime.5–7 While various OSCs, including organic-inorganic hybrid perovskite8–10, crystalline silicon11, and Cu(In, Ga)(Se,S) solar cells12, have been studied extensively to achieve efficiency greater than 30%, environmental reliability issues need to be addressed for the realization of highly reliable OSCs.13–15 The environmental reliability issues are mostly related to reactive gases13,15, UV light6,16, and heat4,17; these elements should be blocked to address these reliability issues. Therefore, to achieve the long-term reliability of OSCs, thin film passivation, which combines multiple functionalities, is required. However, previously proposed passivation strategies concentrated on the development of passivation with only a single function of a gas diffusion barrier (GDB) or IR reflectance or UV reflectance (RUV).13,16,18 Reliability issues related to environmental factors have still not been resolved; hence, further functionally customized thin film passivation technology should be developed. In this study, we demonstrate a low-temperature, simple, and effective gas diffusion multibarrier (GDM) with


Page 2 of 21

Page 3 of 21 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


UV and heat rejection capability. The proposed thin film passivation layer is composed of a UV filter/Ag/GDB/polymer structure that not only optically blocks UV light and heat but also physically and chemically prevents water vapor and water to resolve the environmental reliability issues of OSCs. For these functionalities, we introduced a dielectric-metal-dielectric (DMD) structure with functional dielectric layers and a silane-based inorganic/organic hybrid polymer (silamer) layer. In general, the DMD structure has been used as a transparent flexible electrode and as a heat mirror that effectively reflects the light of the IR region.18–20 In addition, the optical properties of DMD structures vary with the optical properties of the dielectric layers.21 The final silamer layer effectively protects the underlying multilayer structure against water and water vapor through chemical interaction at the interface with the GDB film. Therefore, the combination of the DMD based on the functional dielectric layers and a silamer layer enables customized passivation applicable to OSCs.

2. Results and discussion To design the UHGDM structure, we first fabricated a UV filter based on a distributed Bragg reflector (DBR) multilayer structure as a bottom dielectric layer. A DBR multilayer is a periodic structure formed with alternating dielectric layers with different refractive indexes, enabling the blockage of light of a specific wavelength band.22,23 Therefore, to design the UV-reflective and visible-transparent DBR multilayer, zinc sulfide (ZnS, n ~ 2.67) and lithium fluoride (LiF, n ~ 1.32) were alternately fabricated with a 3.5-dyad multistack using thermal evaporation. Each ZnS/LiF layer pair is referred to as a “dyad,” and 0.5 dyads denote an extra ZnS layer. The surface of the DBR multilayer with the outermost ZnS has high surface free energy (SFE), enabling the metal film to be quasi-perfect at ultralow thickness.24,25 On the other hand, LiF is a thermally evaporated material with a very low refractive index and low SFE. In designing the optimized DMD structure, the thickness of the quasi-perfect Ag thin film is important to achieve maximum visible transmittance (Tvis, λ of 400–720 nm).21 In general, thermally evaporated Ag films have exhibited island film growth, and it is well known that the minimum thickness for the formation of a continuous Ag thin film is influenced by the SFE, deposition rate, and vacuum level.21,26,27 In particular, the surface energies of the dielectric layers significantly influence the thickness of a continuous Ag thin film. Therefore, the outermost ZnS is effective to fabricate a transparent DMD structure as a film-forming accelerator. We hence investigated the surface morphologies of Ag films as a function of the thicknesses of the Ag films formed on various dielectric layers. Figure 1 shows scanning electron microscopy (SEM) images of the Ag surface as a function of the thickness (7, 8, and 9 nm) of the Ag film deposited on different types of dielectric layers (MgO/ZnO/Al2O3 nanolaminate (MZA), indium tin oxide (ITO), zinc oxide (ZnO), LiF, molybdenum trioxide (MoO3), and ZnS). The surface morphologies and sheet resistances of the Ag thin films show significant differences according to the bottom dielectric layers. In particular, the ZnS layer enables the formation of a continuous Ag thin film at the lowest thickness (around 8 nm); however, the 9 nm-thick Ag thin film on the LiF layer still shows an island-like morphology, and hence, the sheet resistance was not measured. Therefore, differences in the surface morphology and sheet resistance of the Ag thin film grown on the bottom seed layers result from the difference in the SFE of the dielectric layer. The SFEs of various dielectric layers were calculated using the Owen–Wendt method by measuring the contact angles of water, ethylene glycol, and diiodomethane on the tested surfaces (Table S1). As a result, the surface energy of ZnS was found to be 63.49 dyne/cm, which was much larger than



the surface energy of LiF (43.20 dyne/cm). Table S1 and Figure 1 show the correlation between the SFE and the Ag film growth. However, the LiF surface was not suitable for growing the Ag thin film considering its low SFE, indicated by the island cluster of the Ag film at a thickness of 9 nm. On the other hand, the ZnS surface with relatively high SFE can effectively promote connection with adjacent Ag clusters and provide an effective wetting effect for the ultrathin quasi-perfect Ag formation. Therefore, the UV filter with the outermost ZnS layer helped render the UHGDM considerably more transparent.

Figure 1. SEM images of the Ag surfaces as a function of Ag thickness (7, 8, and 9 nm) deposited on various dielectric layers (MZA nanolaminate, ITO, ZnO, MoO3, LiF, and ZnS). All Ag thin films were deposited with a deposition rate of 2 Å/s.


Page 4 of 21

Page 5 of 21 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 3.5-dyad ZnS/LiF multilayer was optimized through optical calculations based on MATLAB incorporating the transfer-matrix formalism to reflect UV wavelengths of less than 410 nm and to transmit visible light. Figure S1 shows the calculated transmittance in the wavelength range of 350–800 nm according to the thicknesses of ZnS/LiF and the number of dyads. Based on the simulation results, the UV filter was designed with a structure of a 3.5-dyad ZnS (33 nm)/LiF (62 nm) multilayer. It should be noted that we could use a 4.5 dyad ZnS/LiF multilayer not only to cut off the UV light much more effectively but also to obtain a high Tvis. Nevertheless, we fabricated a 3.5-dyad ZnS/LiF multilayer to demonstrate a simple methodology for UHGDMs.

Figure 2. a) Schematic of the low-temperature and water-resistant UHGDM structure based on a DMD structure. b) SEM cross-sectional images of the UV filter/Ag/MZA structure. The inset displays a TEM cross-sectional image of the MZA nanolaminate film with a layer-by-layer structure. Finally, after fabricating the UV filter/Ag (8 nm) structure, MZA nanolaminate as the main GDB and silamer layer as the water-resistant layer were sequentially formed using atomic layer deposition (ALD) and the spincoating method, respectively, to improve the barrier performance, environmental stability, and optical transmittance of the DMD structure.28–30 The MZA nanolaminate was optimized based on quasi-perfect sublayers in terms of barrier functionality and achieved water vapor transmission rates (WVTRs) on the order of ~ 10−5 g/m2/day at a thickness of less than 100 nm.19,28,31 Furthermore, the MZA nanolaminate film was fabricated at a low temperature of 60 °C to prevent the thermal degradation of OEDs in the ALD process. The silamer layer was then spin-coated to form a 150 nm-thick layer, and it was thermally cured for 15 min in an ALD chamber at 60 °C. The measured thickness of the thermally cured silamer layer after spin-coating was obtained using AFM analysis as shown in Figure S2. The AFM measurement result showed that the thickness of the spin-coated silamer layer was approximately 150 nm. Through the synergistic combination of the DMD structure and functional dielectric layers, the designed transparent functional UV- and heat-reflective gas diffusion multibarrier (UHGDM) assembly can effectively block not only optical heat and UV light, but also is impermeable to water vapor and water. Figure 2a shows a schematic of the fabricated UHGDM based on structural and material design. A cross-sectional SEM image of the fabricated UHGDM and a cross-sectional



transmission electron microscopy (TEM) image of the MZA nanolaminate structure are shown in Figure 2b. The MZA nanolaminate based on quasi-perfect sublayers shows a well-separated layer-by-layer structure between sublayers through TEM analysis.

Figure 3. Measured and calculated spectral transmittance of a) UV filter, b) UV filter/Ag, and c) UHGDM structures formed on PET substrates in the range of 350–800 nm. d) Comparison of measured transmittances according to layer formation in the range of 350–2000 nm. Table 1. Optical transmittances of PET, PET/UV filter, PET/UV filter/Ag, and PET/UHGDM.

We compared the measured and calculated spectral transmittance of the UV filter, UV filter/Ag, and UHGDM


Page 6 of 21

Page 7 of 21 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


structures. Figure 3 shows the calculated and measured transmittance of the UV filter, UV filter/Ag, and UHGDM structures in a wavelength range of 350–2000 nm. The measured transmittances of all film structures were almost same as that of the corresponding calculated transmittances. The UV filter showed excellent reflectance at UV wavelengths less than 400 nm. After Ag formation on the UV filter structure, the UV filter/Ag structure showed significant reduction of transmittance in the visible and IR ranges. Through the final application of the MZA nanolaminate to the UV filter/Ag structure for obtaining improved Tvis and excellent barrier performance, the UHGDM structure exhibited significant transmittance improvement from 55.355 to 71.799% in the visible region and maintained excellent reflectance for IR wavelengths (Table 1). The Tvis and T550 nm of the UHGDM assembly were almost same as the corresponding values of the UV filter owing to the significant transmittance improvement induced by the DMD structure. Based on the synergistic combination of the DMD structure and functional dielectrics, the UHGDM structure was effectively designed to achieve optical properties suitable for use in OED passivation.

Figure 4. a) WVTR values of various oxide films measured at 30 °C/90% RH. b) Normalized conductances of UV filter/Ag, MZA, and UHGDM under 60 ° C/90% RH. c) Ca test results of MZA and MZA/silamer under 90 °C/90% RH. Transmittance changes of d) UV filter, e) UV filter/Ag, and f) UHGDM structures before and after 60 °C/90% RH storage for 48 h.

Table 2. Calculated lag times and WVTR values of UV filter/Ag, MZA, and MZA/silamer under 60°C/90% RH



Next, we evaluated the barrier performance and environmental stability of the water-resistant UHGDM structure. The MZA nanolaminate structure exhibited substantially improved GDB properties and mechanical properties in comparison to the Al2O3 single layer. In particular, the ALD-based nanolaminate structure can be optimized through the optimization of its constituent sublayers in terms of its impermeable and mechanical properties.19,31 We fabricated an alternately multistacked structure composed of MgO, ZnO, and Al2O3 sublayers at a low temperature of 60 °C. It is well known that ZnO and MgO thin films grown by ALD exhibit poor barrier performance owing to increased crystallinity with increasing film thickness.19,31,32 However, ZnO and MgO ALD sublayers can be effectively used as a GDB when their crystallinity is controlled, and chemical bonds then form at the interfaces with the Al2O3 sublayers. The ZnO film was etched by a trimethylaluminum (TMA) precursor for the Al2O3 ALD film. The etching process between Al2O3 and ZnO forms chemical bonding at the interfaces, making the MZA nanolaminate denser and more flexible. In addition, the MgO film formed an aluminate phase with the Al2O3 film, resulting from differences in the electronegativities between Al2O3 and MgO.19 In other words, chemical bonding generated at the interfaces of Al2O3/ZnO and Al2O3/MgO makes the MZA nanolaminate highly impermeable and robust. In addition, we previously studied that the MZA nanolaminate showed the best WVTR value at a thickness of around 60 nm and exhibited much better barrier performance in comparison to the 60 nm-thick other single layers under 30°C /90% RH (Figure 4a).28,31 Although the 60-nm-thick ZnO/MgO (ZM) nanolaminate is based on a nanolaminate system, its barrier performance with a WVTR on the order of 10-3 g/m2/day exhibited a limitation for use as a GDB. On the other hand, the Al2O3-based MZA nanolaminate exhibited a WVTR on the order of 10-5 g/m2/day at a 60 nm. Therefore, although the UV filter/Ag structure exhibited poor barrier performance on the order of 10-1 g/m2/day, the MZA worked as a main GDB owing to its excellent barrier properties that are attributed to the formation of densely packed aluminate phases at the interfaces and defect-decoupling, multi-interfacial effects between sublayers.31,33 The corrosion-resistant properties of the UHGDM structure according to the presence of the silamer were evaluated to investigate the effective function of the silamer layer as a protective layer. To calculate the lag times and WVTR values of each barrier film, the barrier films were stored under a harsh condition of 60°C /90% RH. Although WVTRs of MZA and MZA/silamer did not differ significantly in the steady-state region, their difference was significant at lag times of 62.40 and 111.84 hours, respectively. (Figure 4b and Table 2) This difference in lag time is due to the additional formation of the silamer layer as a protective layer.28,29 The silamer layer enables the underlying MZA film to be corrosion- and gas permeation resistant in harsh environments. In addition, Figure 4c shows Ca test results on the MZA and MZA/silamer conducted under the extremely harsh condition of 90°C/90% RH. Although the MZA nanolaminate was designed to obtain high impermeability to reactive gases, the MZA film easily degraded in the extremely harsh


Page 8 of 21

Page 9 of 21 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


temperature/humidity environment. However, the environmental stability of the MZA capped with the silamer layer was significantly improved in comparison to the bare MZA nanolaminate. As shown in Figure S3, although the barrier performance of the silamer layer itself was poor, the silamer layer with three-dimensional silica layers effectively filled pinhole defects of the MZA surface during thermal curing and effectively protected the underlying MZA nanolaminate from external environments. These synergistic effects make the UHGDM structure more impermeable and chemically stable. Therefore, the UHGDM structure can be used as a wearable functional passivation layer suitable for wearable electronic devices exposed to water by washing and weather.

Figure 5. a) UV aligner equipment for UV reflection tests. b) UV-reflective capabilities of various substrates and film structures. We evaluated the environmental stability of the UHGDM structure against harsh conditions of 60 °C/90% RH. The UV filter, UV filter/Ag, and UHGDM structures were stored for two days under 60 °C/90% RH, following which their optical transmittances were measured before and after storage. From the results, the UV filter and UV filter/Ag structures degraded under high temperature and humidity owing to environmental instability,



whereas the UHGDM structure almost fully maintained its transmittance by minimizing the permeation of water vapor and oxygen due to the excellent moisture- and water-resistant properties of the MZA nanolaminate/silamer structure. Thus, the functionally and optically designed UHGDM exhibited excellent environmental stability, and as such, is applicable to various OEDs employed outdoors. The UV-reflective capability of the UHGDM structure was evaluated under real UV exposure. UV exposure was achieved using UV aligner equipment with a specified UV wavelength range of 350–380 nm, with a UV light intensity meter providing an intensity reading of the UV light (Figure 5a). Figure 5b shows the UVfiltering results of various substrates and thin films. Bare glass and bare polyethylene terephthalate (PET) substrates could hardly block UV light. In addition, transparent indium tin oxide (ITO) and semitransparent Ag thin film, which are commonly used as electrodes, did not effectively block UV light. However, the UV filterbased structures showed a UV rejection capability of 97% or more. Therefore, our designed UHGDM structure was optically transparent while effectively blocking UV light through real UV exposure.

Figure 6. a) Schematic of thermal reflection test. b) Samples remained fixed to the bars. c) Measured temperature profiles of various samples formed on glass substrates after exposure to a heat source for 30 s. After the UV reflection test, a heat reflection test was conducted to investigate the heat rejection capability of the UHGDM structure. First, we fabricated OSC devices with the ITO (150 nm)/ZnO (40 nm)/poly[N-9′heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]:[6,6]-phenyl-C71 butyric acid methyl ester (PCDTBT:PC70BM, 10 nm)/MoOx (10 nm)/Al (100 nm) structure to investigate the correlation between the storage temperature and electrical characteristics of commonly studied OSCs.34–36 To prevent degradation induced by water vapor and oxygen, the fabricated OSCs were encapsulated with a glass lid. The current density–voltage (J–V) characteristics of the OSCs were measured after being stored for 2 h in a vacuum chamber at 60, 70, and 80 °C (Figure S4). From the measurements, the OSCs stored in a chamber at 70 and 80 °C showed significant differences in the J–V characteristics. However, no significant changes were observed in the J–V characteristics of the OSCs stored at 60 °C. It is well known that most OSCs suffer from thermal stress at high temperatures, presumably due to the poor thermal stability of the organic small molecule-


Page 10 of 21

Page 11 of 21 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


PCDTBT:PC70BM.13–15,37 Therefore, determining the process temperatures that do not cause device degradation is important in optimizing encapsulation technologies. We confirmed that the thermal stability of the PCDTBT:PC70BM-based OSCs and the maximum process temperature for UHGDM is limited to 60 °C. The UV filter, UV filter/Ag, and UHGDM structures deposited on glass substrates and bare glass were evaluated together to investigate the thermal reflectance effects induced by the sequential formation of each layer. For reliable temperature measurements, the surface emissivity and distance between the IR camera and samples should be identical. As shown in Figure 6a, temperatures of the back side of glass substrates with various film structures were measured using an IR camera for identical emissivity (glass, ε = 0.9). In addition, a thermal barrier was placed in front of the heat source to minimize heat transfer by convection and the positions of the samples remained fixed on the bars (Figures 6a and b). The fixed samples were exposed to the farinfrared heat source for 30 s and the measurement results are shown in Figure 6c. The UHGDM and UV filter/Ag structures cut off heat effectively, consistent with IR transmittance measurements, whereas the other structures without the ultrathin Ag film showed a significant temperature increase up to 46 °C. Therefore, the UHGDM structure demonstrated a high Tvis of more than 70% and high IR reflectance through thickness optimization despite the use of a semitransparent Ag thin film.



Figure 7. a) J–V characteristics of glass-encapsulated OSCs without UHGDM after UV light exposure. b) J–V characteristics of glass-encapsulated OSCs with UHGDM after UV light exposure. c) J–V characteristics of OSC passivated with UHGDM before and after water immersion for 30 min. d) Shelf lifetimes of bare OSC and UHGDM-passivated OSC under 30 °C/90% RH. After another UHGDM-passivated OSC was immersed in water for 30 min, its shelf life was measured. (e) Current density–voltage and (f) current efficiency–current density curves of PhOLEDs before and after the bending test. (Inset: Photograph of the red-emitting PhOLED passivated with the UHGDM).


Page 12 of 21

Page 13 of 21 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


Finally, we demonstrated the effects of improved reliability induced by the application of UHGDM to OSCs in terms of UV light, heat, and reactive gases. First, prior to the OSC fabrication, the UHGDM structure was formed on the back side of a glass substrate and an OSC was formed on the front side of a glass substrate. The OSCs were then encapsulated with a glass lid to prevent degradation induced by water vapor and oxygen. The J–V characteristics of the OSCs without and with the UHGDM were evaluated before and after UV exposure as a function of time (Figure 7 and Table S1). UV light was illuminated on the OSC devices using a UV aligner, as shown in Figure 4a. Figure 7a shows the J–V characteristics of bare OSCs exposed to UV light for 0, 0.5, and 2 h. The OSCs show significant performance degradation by UV exposure; the degradation is more severe for longer exposure times. In other words, UV light was detrimental to OSCs composed of organic layers and therefore should be minimized through the application of a transparent optical passivation layer for the longterm reliability of outdoor OSCs exposed to sunlight. Figure 7b shows the UV-induced performance degradation levels of OSCs with the UHGDM. Despite UV exposure for 2 h, OSCs passivated with the UHGDM show negligible performance degradation in comparison to the J–V characteristics of pristine OSCs without the UHGDM. After the OSCs with the UHGDM were exposed to UV light for 2 h, their open-circuit voltage (Voc) level was maintained at 0.84 V, similar to the initial value; however, the short-circuit current density (Jsc) dropped from 15.03 to 13.54 mA/cm2 due to light blocking resulting from the UHGDM structure. In other words, OSCs with the UHGDM showed excellent reliability against UV light even though they showed a slight decrease in performance because of a decrease in transmittance induced by the UHGDM. After testing the UV rejection capability of the UHGDM, a UHGDM was passivated directly into OSCs to investigate the change in the J–V characteristics and shelf lifetimes of OSCs according to exposure to water and accelerated conditions. As shown in Figure 7c, owing to the excellent water-resistant properties of the UHGDM, the J–V characteristics of the passivated OSC did not degrade at all after immersion in water. The synergistic MZA/silamer structure effectively blocked water ingress to the UV filter/Ag and OSC. Shelf life tests for bare OSC, UHGDM-passivated OSC, and UHGDM-passivated, water-immersed OSC were then conducted under accelerated conditions of 30 °C/90% RH (Figure 7d). The normalized power conversion efficiency (PCE) of the OSC without passivation abruptly decreased to 10% within 10 days upon exposure to a humidity environment, whereas the passivated OSC showed little efficiency degradation after 40 days due to the excellent barrier functionality of the UHGDM, as expected. In addition, after passivation of the OSC, the passivated OSC immersed in water for 30 min recorded the same efficiency after 40 days in comparison to the passivated OSC unexposed to water. Then, to confirm the mechanical stability of the UHGDM-passivated organic devices, thermally evaporated OLEDs were used. The OSCs based on a high-temperature process were difficult to form stably on plastic substrates, and they thus demonstrated low yield and low efficiency. Instead, we fabricated the phosphorescent OLEDs (PhOLEDs) composed of 4,4 ′ -bis(N-phenyl-1-naphthylamino)biphenyl (NPB, 50 nm)/Ag (30 nm)/MoO3(5 nm)/NPB (68 nm)/bis(10-hydroxybenzo[h] quinolinato)beryllium complex: tris(1phenylisoquinoline)iridium (Bebq2: 8% Ir(ppy)3, 70 nm)/lithium quinolate (Liq, 1 nm)/aluminum (100 nm) on a 50-µm-thick PET substrate using a thermal evaporation system. The J–V–L characteristics of the UHGDMpassivated OLEDs were compared before and after the bending test with a bending radius of 10 mm. Figures 7e and f show the J–V–L curves of the PhOLED devices. After a tensile strain is applied to the OLED devices, the electric-optical characteristics of the devices were maintained without little change. However, the OLED cells were cracked at a smaller bending radius, indicating unstable device operation. This result is attributed to the



poor flexibility of the UV filter composed of brittle and thick ZnS and LiF films, respectively. Although the UV filter was more brittle than the other layers, the mechanical flexibility of the UHGDM structure was significantly improved by the introduction of the silamer layer. The UV filter/Ag/MZA and UV filter/Ag/MZA/silamer (UHGDM) fabricated on PET substrates were bent up to a bending radius of 3 mm. As shown in Figure S5, the multilayer without the silamer layer show partial cracking and delamination of the UV filter, leading to uneven surfaces and a change in transmittance. On the other hand, the UHGDM almost maintained uniform and clean surface and visible transmittance even after bending. Therefore, the silamer layer acts as a stress-relieving as well as a protective layer. Through a series of measurements, our designed UHGDM not only effectively prevented water penetration, but also did not degrade even when exposed to water owing to the water-resistant silamer layer; thus, we demonstrated its applicability for wearable encapsulation technologies. However, the UV filter needs to be fabricated using a UV-blocking organic single layer or an organic multilayer composed of largely different refractive indexes for the realization of highly flexible UHGDM-passivated device.

3. Conclusion We demonstrated a low-temperature and corrosion-resistant GDM with UV and heat rejection capability, based on a synergistic combination of a DMD structure and functional dielectric layers as a customized passivation layer for OEDs. The proposed UHGDM was designed with a multistacked structure of a sequential UV filter, Ag, nanolaminate, and silamer, using a process temperature of less than 60 °C to realize highly efficient and reliable OEDs, thus overcoming the reliability issues caused by environmental factors such as UV, heat, and reactive gases. The transparent UHGDM structure showed excellent UV and heat rejection capability in UV and heat reflection tests owing to the combination of the UV filter and the DMD structure. In addition, the UHGDM structure achieved a WVTR value of 1.58 × 10−5 g/m2/day and exhibited excellent water-resistant properties through the introduction of the GDB/silamer structure. Finally, with a functionally well-designed UHGDM structure, the OSCs were passivated and showed excellent environmental reliability for even more severe UV and temperature/humidity exposure than the outside environment. Therefore, based on various characterization evaluations and device reliability tests, our UHGDM provides an effective solution customized to overcome all environmental reliability issues. In addition, the UHGDM-passivated OLEDs were fabricated to evaluate their mechanical stability, and they maintained their electro-optical characteristics in the bending test with a bending radius of 10 mm. Therefore, the multifunctional UHGDM structure can be used not only as an effective passivation layer for the actively investigated perovskite solar cells, where their absorber is highly sensitive to environmental factors, but also as UV- and heat-reflective automotive tinting films that can warm the inside of a car in winter and cool it in summer. Given that the proposed UHGDM structure can be fabricated in situ sequentially via ALD and is compatible with commercially available OEDs, it is expected to accelerate the commercialization of OSCs and OLEDs that require effective UV and heat blocking. In the near future, further work on transparent conductive UHGDMs will be conducted for various practical applications as an electrode beyond the present UHGDM proposed as an insulating multibarrier structure.

4. Experimental Section


Page 14 of 21

Page 15 of 21 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


Fabrication of the UHGDM structure. The UV filter and Ag thin film were deposited on a 125-um-thick PET substrate using thermal evaporation. The UV filter composed of 3.5-dyad multi-stacked ZnS(33 nm)/LiF(62 nm) was fabricated by thermal evaporation with a constant deposition rate of 1 Å/s at vacuum pressure of 1 × 10−6 Torr and then a 8-nm-thick Ag film was sequentially deposited at a constant deposition rate of 2 Å/s. The UV filter/Ag structure was transferred to an ALD chamber maintained at 60 °C to deposit a MZA nanolaminate. The growth rates of MgO, ZnO, and Al2O3 films deposited at 60°C are 0.95, 0.98, and 0.79 Å/cycle, respectively. The optimized cyclic ratio of MgO, ZnO, and Al2O3 sublayers for MZA nanolaminate was obtained to form 1-nm-thick sublayers. The silamer layer was spin-coated to be 150-nm-thick. The silamer layer based on methanol as solvent was thermally curable for 15 min in an ALD chamber maintained at a vacuum level of 3 × 10−2 Torr and a temperature of 60 °C for complete layer formation. Device Fabrication and Characterization. OSCs on a 150-nm-thick ITO-coated glass substrate (2.5 cm × 2.5 cm) were fabricated using spin-coating and thermal evaporation. A sol-gel ZnO (1M) solution was spin coated on an ITO-coated glass substrate at 3000 rpm for 1 min and a ZnO film was annealed at 150°C for 10min. PCDTBT:PC70BM (1:4 wt%) was spin coated on the ZnO film at 900 rpm for 40s and thereafter the film was dried in a nitrogen filled glove box for 1 hour. The samples were transferred to a thermal evaporator and MoOx (10nm) and Al (100nm) were evaporated sequentially. J-V characteristics of the devices were measured with a source-measure unit (Keithley2611A) and a solar simulator (CEP-25ML, Bunkoukeiki). The samples were kept in a mini-vacuum chamber with quartz glass to illuminate light from an AM 1.5G solar simulator. To calibrate 1 sun (AM 1.5G), a crystalline silicon reference cell was used. The total transmittance and reflectance were obtained using a UV/VIS/NIR spectrophotometer (Perkin Elmer, Lambda 950) with a 150 mm integrating sphere. Thin Film Characterization. For WVTR measurements through an electrical Ca test, the patterned Al (100 nm) and Ca (250 nm) films were deposited sequentially via thermal evaporation on a glass substrate (4 cm × 2.5 cm). The passivated plastic film was then attached to a Ca-deposited cell using UV-curable sealant (XNR5570, Japan). The Ca sensors were kept in 30 °C and 90% RH and WVTR measurement and real-time resistance measurements were carried out using a Keithely source-meter (DMM 2750, USA). A UV reflection test was conducted using a UV aligner (MIDAS, MDA-8000) and a UV intensity meter reads the transmitting UV light through thin films. In addition, in the heat reflection test, IR images and temperature profiles of each sample were taken by an IR camera (FLIR T450sc).



5. ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Calculated transmittance in the wavelength range of 350 - 800 nm according to the thicknesses of ZnS/LiF and the number of dyads; Ca test result of the 150-nm-thick silamer layer under 60°C/90 % RH; Schematic of the synergistic multilayer structure composed of MZA nanolaminate and silmer with randomly formed silica layers; J-V characteristics of glass-encapsulated OSCs before and after heating at 80, 70, and 60 °C for 2 hours, respectively; Solar cell parameters of OSCs according to the presence of UHGDM before and after UV exposure;

6. AUTHOR INFORMATION Corresponding Author K.C. Choi.* Author is with the School of Electrical Engineering, the Korea Advanced Institute of Science and Technology, Yuseong-gu, Daejeon 34141, Republic of Korea (corresponding author phone: +82-42-350-3482; fax: +82-42-350-8082; e-mail: kyungcc@ kaist.ac.kr). ORCID Kyung Cheol Choi: 0000-0001-6483-9516 Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest.

7. ACKNOWLEDGEMENT This work was supported by the Engineering Research Center of Excellence (ERC) Program (Grant No. NRF-2017R1A5A1014708) and the Nano·Material Technology Development Program (Grant No. NRF2016M3A7B4910635) through the National Research Foundation (NRF) funded by Korean Ministry of Science & ICT (MSIT). In addition, this work was supported by the NRF and Korea Institute of Materials Science (KIMS) funded by Korean MSIT (No. PNK5720) and supported by the Technology Innovation Program (20000489, Interactive fiber based wearable display platforms for clothing displays) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea), respectively.

References (1)

Lee, J.; Han, T. H.; Park, M. H.; Jung, D. Y.; Seo, J.; Seo, H. K.; Cho, H.; Kim, E.; Chung, J.; Choi, S.Y.; Kim, T.-S.; Lee, T.-W.; Yoo, S. Synergetic Electrode Architecture for Efficient Graphene-Based Flexible Organic Light-Emitting Diodes. Nat. Commun. 2016, 7, 1–9.


Page 16 of 21

Page 17 of 21 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


(2)

Yokota, T.; Zalar, P.; Kaltenbrunner, M.; Jinno, H.; Matsuhisa, N.; Kitanosako, H.; Tachibana, Y.; Yukita, W.; Koizumi, M.; Someya, T. Ultraflexible Organic Photonic Skin. Sci. Adv. 2016, 2 (4), 1–9.

(3)

Moon, H.; Seong, H.; Shin, W. C.; Park, W.-T.; Kim, M.; Lee, S.; Bong, J. H.; Noh, Y.-Y.; Cho, B. J.; Yoo, S.; Im, S. G. Synthesis of Ultrathin Polymer Insulating Layers by Initiated Chemical Vapour Deposition for Low-Power Soft Electronics. Nat. Mater. 2015, 14 (6), 628–635.

(4)

Li, X.; Ibrahim Dar, M.; Yi, C.; Luo, J.; Tschumi, M.; Zakeeruddin, S. M.; Nazeeruddin, M. K.; Han, H.; Grätzel, M. Improved Performance and Stability of Perovskite Solar Cells by Crystal Crosslinking with Alkylphosphonic Acid ω -Ammonium Chlorides. Nat. Chem. 2015, 7 (9), 703–711.

(5)

Jørgensen, M.; Norrman, K.; Gevorgyan, S. A.; Tromholt, T.; Andreasen, B.; Krebs, F. C. Stability of Polymer Solar Cells. Adv. Mater. 2012, 24 (5), 580–612.

(6)

Lee, S.-W.; Kim, S.; Bae, S.; Cho, K.; Chung, T.; Mundt, L. E.; Lee, S.; Park, S.; Park, H.; Schubert, M. C.; Glunz, S. W.; Ko, Y.; Jun, Y.; Kang, Y.; Lee, H.-S.; Kim, D. UV Degradation and Recovery of Perovskite Solar Cells. Sci. Rep. 2016, 6 (1), 38150.

(7)

Kwon, J. H.; Choi, S.; Jeon, Y.; Kim, H.; Chang, K. S.; Choi, K. C. Functional Design of DielectricMetal-Dielectric-Based Thin-Film Encapsulation with Heat Transfer and Flexibility for Flexible Displays. ACS Appl. Mater. Interfaces 2017, 9 (32), 27062–27072.

(8)

Matteocci, F.; Cinà, L.; Lamanna, E.; Cacovich, S.; Divitini, G.; Midgley, P. A.; Ducati, C.; Di Carlo, A. Encapsulation for Long-Term Stability Enhancement of Perovskite Solar Cells. Nano Energy 2016, 30, 162–172.

(9)

Tan, H.; Jain, A.; Voznyy, O.; Lan, X.; Arquer, F. P. G. de; Fan, J. Z.; Quintero-Bermudez, R.; Yuan, M.; Zhang, B.; Zhao, Y.; Fan, F.;Li, P.; Quan, L. N.; Zhao, Y.; Lu, Z.-H.; Yang, Z.; Hoogland, S.; Sargent, E. H. Efficient and Stable Solution Processed Planar Perovskite Solar Cell via Contact Passivation. Science (80-. ). 2017, 355 (6326), 722–726.

(10)

Brinkmann, K. O.; Zhao, J.; Pourdavoud, N.; Becker, T.; Hu, T.; Olthof, S.; Meerholz, K.; Hoffmann, L.; Gahlmann, T.; Heiderhoff, R.; Oszajca, M. F.; Rogalla, D.; Chen, Y.; Cheng, B.; Riedl, T. Suppressed Decomposition of Organometal Halide Perovskites by Impermeable Electron-Extraction Layers in Inverted Solar Cells. Nat. Commun. 2017, 8, 1–9.

(11)

System, M. H. V; Assurance, P.; Corporation, I. B. M. ADHESION MEASUREMENT OF THIN FILMS. 1976, 3 (C), 21–42.

(12)

Yang, Y. M.; Chen, Q.; Hsieh, Y.-T.; Song, T.-B.; Marco, N. De; Zhou, H.; Yang, Y. Multilayer Transparent Top Electrode for Solution Processed Perovskite/ Cu(In,Ga)(Se,S)2 Four Terminal Tandem Solar Cells. ACS Nano 2015, 9 (7), 7714-7721

(13)

Lee, Y. Il; Jeon, N. J.; Kim, B. J.; Shim, H.; Yang, T. Y.; Seok, S. Il; Seo, J.; Im, S. G. A Low-



Temperature Thin-Film Encapsulation for Enhanced Stability of a Highly Efficient Perovskite Solar Cell. Adv. Energy Mater. 2018, 8 (9), 1–8. (14)

Mesquita, I.; Andrade, L.; Mendes, A. Perovskite Solar Cells: Materials, Configurations and Stability. Renew. Sustain. Energy Rev. 2018, 82 (May 2017), 2471–2489.

(15)

Asghar, M. I.; Zhang, J.; Wang, H.; Lund, P. D. Device Stability of Perovskite Solar Cells – A Review. Renew. Sustain. Energy Rev. 2017, 77, 131–146.

(16)

Leijtens, T.; Eperon, G. E.; Pathak, S.; Abate, A.; Lee, M. M.; Snaith, H. J. Overcoming Ultraviolet Light Instability of Sensitized TiO2with Meso-Superstructured Organometal Tri-Halide Perovskite Solar Cells. Nat. Commun. 2013, 4, 1–8.

(17)

Habisreutinger, S. N.; Leijtens, T.; Eperon, G. E.; Stranks, S. D.; Nicholas, R. J.; Snaith, H. J. Carbon Nanotube/Polymer Composites as a Highly Stable Hole Collection Layer in Perovskite Solar Cells. Nano Lett. 2014, 14 (10), 5561–5568.

(18)

Kim, H.; Kim, H. S.; Ha, J.; Park, N. G.; Yoo, S. Empowering Semi-Transparent Solar Cells with Thermal-Mirror Functionality. Adv. Energy Mater. 2016, 6 (14), 1–9.

(19)

Kwon, J. H.; Park, J. H.; Lee, M. K.; Park, J. W.; Jeon, Y.; Shin, J. Bin; Nam, M.; Kim, C.; Choi, Y.; Choi, K. C. Low-Temperature Fabrication of Robust , Transparent , and Flexible Thin Film Transistor with Nano-Laminated Insulator. ACS Appl. Mater. Interfaces 2018, 10, 15829–15840.

(20)

Al-Kuhaili, M. F.; Al-Aswad, a. H.; Durrani, S. M. a.; Bakhtiari, I. a. Transparent Heat Mirrors Based on Tungsten Oxide–silver Multilayer Structures. Sol. Energy 2009, 83 (9), 1571–1577.

(21)

Yun, J. Ultrathin Metal Films for Transparent Electrodes of Flexible Optoelectronic Devices. Adv. Funct. Mater. 2017, 27 (18), 1606641.

(22)

Kim, E.; Jang, W. J.; Kim, W.; Park, J.; Lee, M. K.; Park, S. H. K.; Choi, K. C. Suppressed Instability of A-IGZO Thin-Film Transistors Under Negative Bias Illumination Stress Using the Distributed Bragg Reflectors. IEEE Trans. Electron Devices 2016, 63 (3), 1066–1071.

(23)

Dubey, R. S.; Ganesan, V. Fabrication and Characterization of TiO2/SiO2based Bragg Reflectors for Light Trapping Applications. Results Phys. 2017, 7, 2271–2276.

(24)

Yang, D. Y.; Lee, S.-M.; Jang, W. J.; Choi, K. C. Flexible Organic Light-Emitting Diodes with ZnS/Ag/ZnO/Ag/WO3 Multilayer Electrode as a Transparent Anode. Org. Electron. 2014, 15 (10), 2468–2475.

(25)

Kim, D.-Y.; Han, Y. C.; Kim, H. C.; Jeong, E. G.; Choi, K. C. Highly Transparent and Flexible Organic Light-Emitting Diodes with Structure Optimized for Anode/Cathode Multilayer Electrodes. Adv. Funct. Mater. 2015, 25 (46), 7145–7153.


Page 18 of 21

Page 19 of 21 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


(26)

Cattin, L.; Bernède, J. C.; Morsli, M. Toward Indium-Free Optoelectronic Devices: Dielectric/Metal/Dielectric Alternative Transparent Conductive Electrode in Organic Photovoltaic Cells. Phys. Status Solidi Appl. Mater. Sci. 2013, 210 (6), 1047–1061.

(27)

Lee, S. M.; Kwon, J. H.; Kwon, S.; Choi, K. C. A Review of Flexible OLEDs Toward Highly Durable Unusual Displays. IEEE Trans. Electron Devices 2017, 64 (5), 1922–1931.

(28)

Kwon, J. H.; Jeon, Y.; Choi, S.; Kim, H.; Choi, K. C. Synergistic Gas Diffusion Multilayer Architecture Based on the Nanolaminate and Inorganic-Organic Hybrid Organic Layer. J. Inf. Disp. 2018, 19 (3), 135-142.

(29)

Kwon, J. H.; Jeong, E. G.; Jeon, Y.; Kim, D.; Lee, S.; Choi, K. C. Design of Highly Water Resistant , Impermeable , and Flexible Thin- Film Encapsulation Based on Inorganic / Organic Hybrid Layers. ACS Appl. Mater. Interfaces 2019, 11, 3251–3261.

(30)

Jeong, E. G.; Jeon, Y.; Cho, S. H.; Choi, K. C. Textile-based washable polymer solar cells for optoelectronic modules: Toward self- powered smart clothing. Energy Environ. Sci., 2019, DOI: 10.1039/c8ee03271h

(31)

Kwon, J. H.; Jeon, Y.; Choi, S.; Park, J. W.; Kim, H.; Choi, K. C. Functional Design of Highly Robust and Flexible Thin-Film Encapsulation Composed of Quasi-Perfect Sublayers for Transparent, Flexible Displays. ACS Appl. Mater. Interfaces 2017, 9 (50), 43983–43992.

(32)

Kwon, J. H.; Jeon, Y.; Choi, K. C. Robust Transparent and Conductive Gas Di Ff Usion Multibarrier Based on Mg- and Al-Doped ZnO as Indium Tin Oxide-Free Electrodes for Organic Electronics. ACS Appl. Mater. Interfaces 2018, 10, 32387–32396.

(33)

Meyer, J.; Schmidt, H.; Kowalsky, W.; Riedl, T.; Kahn, a. The Origin of Low Water Vapor Transmission Rates through Al[Sub 2]O[Sub 3]/ZrO[Sub 2] Nanolaminate Gas-Diffusion Barriers Grown by Atomic Layer Deposition. Appl. Phys. Lett. 2010, 96 (August 2015), 243308.

(34)

Wang, D. H.; Park, K. H.; Seo, J. H.; Seifter, J.; Jeon, J. H.; Kim, J. K.; Park, J. H.; Park, O. O.; Heeger, A. J. Enhanced Power Conversion Efficiency in PCDTBT/PC70BM Bulk Heterojunction Photovoltaic Devices with Embedded Silver Nanoparticle Clusters. Adv. Energy Mater. 2011, 1 (5), 766–770.

(35)

Albrecht, S.; Schäfer, S.; Lange, I.; Yilmaz, S.; Dumsch, I.; Allard, S.; Scherf, U.; Hertwig, A.; Neher, D. Light Management in PCPDTBT:PC70BM Solar Cells: A Comparison of Standard and Inverted Device Structures. Org. Electron. physics, Mater. Appl. 2012, 13 (4), 615–622.

(36)

Constantinou, I.; Lai, T. H.; Hsu, H. Y.; Cheung, S. H.; Klump, E. D.; Schanze, K. S.; So, S. K.; So, F. Effect of Thermal Annealing on Charge Transfer States and Charge Trapping in PCDTBT:PC70BM Solar Cells. Adv. Electron. Mater. 2015, 1 (9), 1–5.

(37)

Li, Z.; Ho Chiu, K.; Shahid Ashraf, R.; Fearn, S.; Dattani, R.; Cheng Wong, H.; Tan, C. H.; Wu, J.;



Cabral, J. T.; Durrant, J. R. Toward Improved Lifetimes of Organic Solar Cells under Thermal Stress: Substrate-Dependent Morphological Stability of PCDTBT:PCBM Films and Devices. Sci. Rep. 2015, 5 (August), 1–9.


Page 20 of 21

Page 21 of 21 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


Table of Contents


Low-Temperature and Corrosion-Resistant Gas Diffusion Multibarrier

Recommend Documents