Browsing by Issue Date, starting with "2020-06-18"

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Germanium Possessing Facet-Specific Trap States and Carrier Lifetimes
(2020-06-18)
Tan, Chih-Shan
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Lu, Ming-Yen
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Peng, Wei-Hao
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Chen, Lih-Juann
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Huang, Michael H.
Previously, the notable differences in the band structure and changes in bond length and bond distortion between the semiconducting and metal-like planes of germanium have been used to understand the facet-dependent electrical conductivity properties of germanium wafers. To gain further insights into the appearance of electrical facet behaviors, impedance measurements were performed on the Ge{111}, {110}, and {100} wafers. Impedance data and several conductivity-related parameters were used to produce a diagram showing the amount of trap states and the trap state energies. The trap states are found within the germanium band gap with a facet-specific distribution of energies. Compared to the {100} and {110} wafers, the Ge{111} wafer has the lowest trap state density in the probed voltage range. This is consistent with its best conductivity property, as trap states hinder the direct excitation of electrons to the conduction band. Carrier lifetime can also be obtained from the impedance data. The {111} surface generally has the shortest carrier lifetime, which is related to its high electrical conductivity. Interestingly, diffuse reflectance and ultraviolet photoelectron spectral (UPS) measurements yield the smallest Schottky barrier between Ag and the most conductive Ge{111} surface, showing this approach to understanding electrical facet effects can still be useful despite its inadequacy to account for the facet-specific conductivity behaviors of Si wafers. However, one should not rely solely on the experimentally determined Schottky barriers to explain electrical facet effects.
Effect of Lauric Acid on the Thermal and Mechanical Properties of Polyhydroxybutyrate (PHB)/Starch Composite Biofilms
(2020-06-19)
Adorna, Joemer A., Jr.
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Aleman, Camelle Kaye A.
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Gonzaga, Ian Lorenzo E.
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Pangasinan, Jamela N.
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Sisican, Kim Marie D.
Polyhydroxybutyrate (PHB) is a biopolymer of natural origin, one of the suitable alternatives for synthetic plastics. However, pure PHB has a high production cost, is relatively brittle, and has poor processability, hence its limited application. Combining PHB with biomass fillers and plasticizers can significantly improve the properties of the polymer, leading to its commercial usage. In this study, PHB was incorporated with starch (S) as a cheap biomass filler and lauric acid (LA) as a potential plasticizer. The PHB/S/LA composites were prepared using a modified solvent casting method with the incremental addition of LA. The PHB/S ratio was maintained at a ratio of 80/20 (w/w). Physicochemical characterization via EDS, XRD, and FTIR proved that the composite components have blended through nucleation and plasticization processes. The morphology of the PHB/S blends was found to be a heterogeneous matrix, with decreased inhomogeneity upon the addition of LA in the composite. Thermal characterization done by TGA and DSC showed that the thermal properties of PHB/S films improved with the addition of LA. Mechanical tests (UTM) proved that the elastic strain of the films also increased with the addition of LA, although the tensile strength decreased slightly compared to pure PHB/S. Overall, the results of this study provide baseline information on the improvement of PHB-based bioplastics.
Applications of Tamm plasmon-liquid crystal devices
(2020-06-20)
Jeng, Shie-Chang
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影像與生醫光電研究所
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Institute of Imaging and Biomedical Photonics
The Tamm-plasmon-polariton (TPP) occurs at the interface between a metallic film and the photonic-crystal (PC) substrate. Unlike conventional surface-plasmon-polariton (SPP), TPP can be directly excited by both the transverse electric (TE) and transverse magnetic (TM) electromagnetic waves without using additional coupling optics. The fact that the optical functionality of most plasmonics devices is determined after fabrication limits their applications. Tunable SPP devices by applying liquid crystals (LCs) have been widely demonstrated due to their large birefringence and easy controllability via external stimuli. However, actively tuning TPP is difficult because the localised electric field is between the metallic film and PC substrate, the change of refractive index above the metallic film has only small influences on TPP. This article is intended to briefly review recent progress towards using LCs for actively tuning TPP devices. Not only TPP devices can gain benefits from LCs, we will also discuss the applications of TPP for measuring the anisotropy of the alignment films of LC devices. The sensitivity of the proposed scheme will be discussed.
Liquid crystal-based capacitive, electro-optical and dielectric biosensors for protein quantitation
(2020-06-20)
Lee, Mon-Juan
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Lee, Wei
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光電學院
;
College of Photonics
The electrical, electro-optical and dielectric properties of liquid crystals (LCs) are routinely manipulated in liquid-crystal display (LCD) devices, but their potential application in the development of biosensors is still in a nascent stage. In this review, utilising the electrical properties, electro-optical effect and dielectric anisotropy in LCs, we provide insights into several possible modes of label-free biodetection and describe how capacitance, electro-optical and dielectric measurements of various LCs assist in quantitative analysis of biomolecules. It is concluded that the electrically induced biosensing techniques proposed here provides new incentives for researchers to study the interaction between LCs and biomolecules and to resolve technical hurdles facing the development of LC-based biosensors.
Site-Selective Deposition of a Cobalt Cocatalyst onto a Plasmonic Au/TiO2 Photoanode for Improved Water Oxidation
(2020-06-22)
Okazaki, Megumi
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Suganami, Yoshiki
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Hirayama, Naoki
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Nakata, Hiroko
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Oshikiri, Tomoya
Plasmonic Au/TiO2 thin film works as a stable water oxidation photoanode. Here we show that site-selective deposition of nanosized CoOx as a water oxidation cocatalyst at the edge of Au nanoparticles on the TiO2 film improves the photoelectrochemical water oxidation activity. The nanosized CoOx was deposited by a photoassisted electrochemical method onto the Au/TiO2 thin film. The CoOx loading amount was controllable by changing the amount of electric charge that flowed during the deposition, which influenced the photoelectrochemical performance. Under visible light, the optimized CoOx/Au/TiO2 thin film generated stable photoanodic current, which was similar to 3 times higher than that obtained using Au/TiO2.
Quantifying sediment mass redistribution from joint time-lapse gravimetry and photogrammetry surveys
(2020-06-22)
Mouyen, Maxime
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Steer, Philippe
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Chang, Kuo-Jen
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Le Moigne, Nicolas
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Hwang, Cheinway
The accurate quantification of sediment mass redistribution is central to the study of surface processes, yet it remains a challenging task. Here we test a new combination of terrestrial gravity and drone photogrammetry methods to quantify sediment mass redistribution over a 1 km(2) area. Gravity and photogrammetry are complementary methods. Indeed, gravity changes are sensitive to mass changes and to their location. Thus, by using photogrammetry data to constrain this location, the sediment mass can be properly estimated from the gravity data. We carried out three joint gravimetry-photogrammetry surveys, once a year in 2015, 2016 and 2017, over a 1 km(2) area in southern Taiwan, featuring both a wide meander of the Laonong River and a slow landslide. We first removed the gravity changes from non-sediment effects, such as tides, groundwater, surface displacements and air pressure variations. Then, we inverted the density of the sediment with an attempt to distinguish the density of the landslide from the density of the river sediments. We eventually estimate an average loss of 3.7 +/- 0.4 x 10(9) kg of sediment from 2015 to 2017 mostly due to the slow landslide. Although the gravity devices used in this study are expensive and need week-long surveys, new instrumentation currently being developed will enable dense and continuous measurements at lower cost, making the method that has been developed and tested in this study well-suited for the estimation of erosion, sediment transfer and deposition in landscapes.
Electrical and optical properties of degenerate and semi-insulating ZnGa2O4: Electron/phonon scattering elucidated by quantum magnetoconductivity
(2020-06-22)
Look, David C.
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Leedy, Kevin D.
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Horng, Ray-Hua
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Santia, Marco D.
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Badescu, Stefan C.
We study the electrical and optical properties of degenerate ZnGa2O4 films grown by metalorganic chemical vapor deposition (MOCVD) on sapphire and semi-insulating films grown by pulsed laser deposition (PLD) on fused silica. After a forming-gas anneal at 700 degrees C, the MOCVD film is highly conducting, with a room-temperature carrier concentration of 2 x 10(20)cm(-3), a mobility of 20cm(2)/V s, and direct bandgap absorptions at 3.65eV and 4.60eV. Under the same annealing conditions, the PLD film is semi-insulating, with a direct bandgap absorption at 5.25eV. The phonon structure, important for electrical and thermal conduction as well as superconductivity and other quantum phenomena, is very complicated due to the large number of atoms (and, thus, phonon branches) in the unit cell. However, we show that the phonon contributions to electron mobility (mu(ph)) can be directly measured by quantum-based magnetoconductivity over the temperature span T=10-200 K. From an approximate analytical formula, mu(ph) = function (T-ph, T), we calculate an effective phonon energy kT(ph)(T) that takes account of all phonon contributions at temperature T. For T=10-200K, the value of kT(ph) ranges from about 10 to 90meV, consistent with the energy range of the ZnGa2O4 phonon density of states (at 0K) calculated by density functional theory. The total measured mobility can then be modeled by mu(-1)(tot) = mu(-1)(ii) + mu(-1)(ph), where mu(ii) is the mobility due to ionized-impurity scattering. With a high bandgap, controllable conductivity, high breakdown voltage, and bulk-growth capability, ZnGa2O4 offers opportunities for high-power electronics and UV detectors. Published under license by AIP Publishing.
Interfacial Structure-Modulated Plasmon-Induced Water Oxidation on Strontium Titanate
(2020-06-22)
Shi, Xu
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Li, Xiaowei
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Toda, Takahiro
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Oshikiri, Tomoya
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Ueno, Kosei
Plasmon-induced carrier transfer at metallic nanoparticle/semiconductor heterojunctions has received great attention because of its tremendous potential in applications, such as photocatalysis and photoelectric and energy conversion. The interfacial structure of the heterojunction is known to play an important role in charge transfer as well as the subsequent chemical reactions. Here, we studied the Au nanoparticle (Au-NP)-loaded (100)-, (110)-, and (111)-oriented single-crystalline strontium titanate (STO) as a model to investigate the effects of interfacial structure on the plasmon-induced charge separation between the metallic nanoparticles and semiconductors. Via photoelectrochemical characterizations, we found that the efficiency of the plasmon-induced water oxidation reaction on STO(100) is more than 1.4 times higher than that on the other two orientation facets. This enhancement was demonstrated to stem from the high oxidation ability of plasmon-induced holes captured in the surface states. Furthermore, the molecular processes of water oxidation were investigated by monitoring the surface oxidation status of Au-NP/STO as intermediates of plasmon-induced water oxidation using in situ electrochemical surface-enhanced Raman spectroscopy. The onset potential of Au-O vibrations on Au-NP/STO(100) was determined to be 0.4 V more negative than that of Au-NP/STO(110), further confirming the higher oxidation ability of the plasmon-induced holes. Our observation provides an opportunity to efficiently modulate plasmon-excited hot-carrier reaction processes for photochemical applications through interfacial engineering.
Switching between spectral broadening and narrowing of the exciton absorption band of a CH3NH3PbI3 film on altering the polarity of an applied electric field
(2020-06-22)
Awasthi, Kamlesh
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Kala, Kannankutty
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Rana, Shailesh
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Diau, Eric Wei-Guang
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Ohta, Nobuhiro
Electric field-induced broadening and narrowing of an exciton absorption band have been observed to depend on the polarity of the applied electric field for methylammonium lead triiodide perovskite (MAPbI(3)) as a thin film sandwiched between a conducting film of fluorine-doped tin oxide (FTO) and an insulating film of poly(methyl methacrylate) (PMMA). The width of the absorption band increased or decreased when the direction of the applied field was toward FTO or PMMA, respectively, indicating that the spectral broadening and narrowing become switchable on altering the direction of the applied electric field. When titanium oxide (TiO2) in a compact layer was introduced between the MAPbI(3) and FTO layers, the linear electric field effect that depended on the polarity was either not observed or decreased significantly although the quadratic field effects on the exciton absorption band were similarly observed with or without the TiO2 layer.
Plasmonic effects of copper nanoparticles in polymer photovoltaic devices for outdoor and indoor applications
(2020-06-22)
Huang, Chien-Lun
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Kumar, Gautham
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Sharma, Ganesh D.
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Chen, Fang-Chung
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交大名義發表
The use of metal nanoparticles (NPs) that can trigger localized surface plasmon resonance (LSPR) is an effective method for improving the performance of organic photovoltaics (OPVs). Currently, most plasmonic NPs are based on noble metals, including gold and silver; their high cost limits their commercial applications in the cost-effective OPVs. Herein, copper (Cu) NPs, which are more abundant and cheaper, are adopted to fabricate OPVs. To avoid oxidation of Cu NPs, they are positioned at the cathode interface, so that their fabrication could be implemented in an inert environment. The resulting OPVs exhibited improved power conversion efficiencies (PCEs) under illumination at 1 sun, and the device enhancement could be attributed to the LSPR effects of Cu NPs. Further, their potential to enhance the performance of OPVs under indoor lighting conditions is evaluated. The enhancement factor of PCEs was higher, while the light source had a lower color temperature. It could be due to the fact that the main plasmonic band of the Cu NPs is localized in the red spectral range. The results reveal the consideration of matching between the LSPR spectral range and the emission spectra of the artificial light sources is very critical for indoor applications.
Nitrogen-Doped Graphene Quantum Dots for Remarkable Solar Hydrogen Production
(2020-06-22)
Tsai, Kai-An
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Hsieh, Ping-Yen
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Lai, Ting-Hsuan
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Tsao, Chun-Wen
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Pan, Hui
We synthesized nitrogen (N)-doped graphene quantum dots (N-GQDs) using a top-down hydrothermal cutting approach. The concentration of N dopants was readily controlled by adjusting the concentration of the N source of urea. When N dopants were incorporated into GQDs, visible absorption was induced by C-N bonds, which created another pathway for generating photoluminescence (PL). Time-resolved PL data revealed that the carrier lifetime of GQDs was increased upon doping with the optimized N concentration. The photoelectrochemical properties of N-GQDs toward water splitting were studied, and the results showed that 2N-GQDs prepared with 2 g of urea produced the highest photocurrent. The photocatalytic activity of 2N-GQDs powder photocatalyst for hydrogen production was also examined under AM 1.5G illumination, showing substantial enhancement over that of pristine GQDs. Electrochemical impedance spectroscopy data further revealed a significant improvement in charge dynamics and reaction kinetics and an increased carrier concentration as a result of N doping.
Analysis of Hydroxyl Radical and Hydrogen Peroxide Generated in Helium-Based Atmospheric-Pressure Plasma Jet and in Different Solutions Treated by Plasma for Bioapplications
(2020-06-22)
Chen, Tsung-Wen
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Liu, Chih-Tung
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Chen, Chao-Yu
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Wu, Mu-Chien
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Chien, Po-Chien
This study systematically analyzed reactive species generated with self-built helium-based low-temperature atmospheric-pressure plasma jet (He-APPJ); we measured the hydroxyl radical (OH) and hydrogen peroxide (H2O2) above surfaces of plasma-treating solutions and in plasma-treated medium (PTM) of different solutions, including deionized water, phosphate buffered saline, and Dulbecco's modified Eagle medium. The effects of adding O(2)into He working gas on OH and H(2)O(2)generation were discussed. The MCF7 cell responses to plasma treatment were also observed. The OH emission (309 nm) in He-APPJ and above surfaces of plasma-treating solutions were analyzed through optical emission spectroscopy, and concentrations of OH and H(2)O(2)in different solutions were measured using terephthalic acid and Amplex Red, respectively. In our plasma system, it was observed that higher conductivity of solutions may cause stronger OH emission above solution. The ingredients of the solution may affect the concentrations of OH and H2O2. Addition of 0.1% O(2)generates strongest OH emission above surfaces of plasma-treating solution with our He-APPJ, and thus, the highest H(2)O(2)concentration in PTM. The MCF7 cell viability is influenced by the H(2)O(2)concentration in PTM. The results of this study can facilitate further study of plasma effects on PTM and cell culture.
The Dust-to-Gas Ratio, Size Distribution, and Dust Fall-Back Fraction of Comet 67P/Churyumov-Gerasimenko: Inferences From Linking the Optical and Dynamical Properties of the Inner Comae
(2020-06-24)
Marschall, Raphael
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Markkanen, Johannes
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Gerig, Selina-Barbara
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Pinzon-Rodriguez, Olga
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Thomas, Nicolas
In this work, we present results that simultaneously constrain the dust size distribution, dust-to-gas ratio, fraction of dust re-deposition, and total mass production rates for comet 67P/Churyumov-Gerasimenko. We use a 3D Direct Simulation Monte Carlo (DSMC) gas dynamics code to simulate the inner gas coma of the comet for the duration of the Rosetta mission. The gas model is constrained by ROSINA/COPS data. Further, we simulate for different epochs the inner dust coma using a 3D dust dynamics code including gas drag and the nucleus' gravity. Using advanced dust scattering properties these results are used to produce synthetic images that can be compared to the OSIRIS data set. These simulations allow us to constrain the properties of the dust coma and the total gas and dust production rates. We determined a total volatile mass loss of (6.1 +/- 1.5) center dot 10(9)kg during the 2015 apparition. Further, we found that power-laws withq=3.7-0.078+0.57are consistent with the data. This results in a total of5.1-4.9+6.0 center dot 109kg of dust being ejected from the nucleus surface, of which4.4-4.2+4.9 center dot 109kg escape to space and6.8-6.8+11 center dot 108kg (or an equivalent of14-14+22cm over the smooth regions) is re-deposited on the surface. This leads to a dust-to-gas ratio of0.73-0.70+1.3for the escaping material and0.84-0.81+1.6for the ejected material. We have further found that the smallest dust size must be strictly smaller than similar to 30 mu m and nominally even smaller than similar to 12 mu m.
Facet-Specific Photocatalytic Activity Enhancement of Cu2O Polyhedra Functionalized with 4-Ethynylanaline Resulting from Band Structure Tuning
(2020-06-24)
Chen, Tzu-Ning
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Kao, Jui-Cheng
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Zhong, Xin-Yan
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Chan, Shang-Ju
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Patra, Anindya S.
Cu2O rhombic dodecahedra, octahedra, and cubes were densely modified with conjugated 4-ethynylaniline (4-EA) for facet-dependent photocatalytic activity examination. Infrared spectroscopy affirms bonding of the acetylenic group of 4-EA onto the surface copper atoms. The photocatalytically inactive Cu2O cubes showed surprisingly high activity toward methyl orange photodegradation after 4-EA modification, while the already active Cu2O rhombic dodecahedra and octahedra exhibited a photocatalytic activity enhancement. Electron, hole, and radical scavenger experiments prove that the photocatalytic charge transport processes have occurred in the functionalized Cu2O cubes. Electrochemical impedance spectroscopy also indicates reduced charge transfer resistance of the functionalized Cu2O crystals. A band diagram constructed from UV-vis spectral and Mott-Schottky measurements reveals significant band energy shifts in all Cu2O samples after decorating with 4-EA. From density functional theory (DFT) calculations, a new band has emerged slightly above the valence band maximum within the band gap of Cu2O, which has been found to originate from 4-EA through band-decomposed charge density analysis. The increased charge density localized on the 4-EA molecule and the smallest electron transition energy to reach the 4-EA-generated band are factors making {100}-bound Cu2O cubes photocatalytically active. Proper molecular decoration represents a powerful approach to improving the photocatalytic efficiency of semiconductors.
Lasing Properties Activation by Constitutional Isomerism of an Electron-Accepting Group
(2020-06-25)
Szukalski, Adam
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Haupa, Karolina A.
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Janczak, Jan
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Przybyl, Bartosz
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Sznitko, Lech
Materials engineering plays a pivotal role considering its manifold applications, i.e., in medicine as individualized drug carriers or in advanced technologies such as optoelectronic devices and others. Recently, increasing interest in the pyrazoline derivatives family of compounds was noticed. In this paper, we report on the constitutional isomerism influence on photophysical properties of low molecular, push-pull type of pyrazole-based organic chromophores. Particularly, we show the ability of optical properties tailoring by changing the substitution of phenyl ring extended by effective electron-accepting moiety in ortho and para positions. Such a structural change in molecule results in a shift of photoluminescence spectra as well as the activation or deactivation of gain mechanism for multimode laser emission. In order to confirm ground state molecular structures for both isomers we performed time-dependent DFT calculations in a solvent environment. In addition, structural analysis of spontaneously grown single crystals was carried out using X-ray spectroscopy. The above-mentioned studies allowed us to define the isomer's molecular geometries and charge distribution in excited and ground states and to distinguish the significant differences in crystallographic structures. Combined experimental and theoretical research have resulted in a hypothesis of the molecular mechanism standing behind observed differences in optical properties of both isomers. Importantly, such an approach can be useful for materials engineering, allowing us to predict the features of novel materials for optoelectronics and photonics.
Linear, mixed-valent homocatenated tri-tin complexes featuring Sn-Sn bonds
(2020-06-25)
Chang, Wei-Chieh
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Raj, Ankit
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Hiramatsu, Hirotsugu
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Li, Han-Jung
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Ziegler, Micah S.
A series of tri-tin complexes((LSn)-Sn-Ph)(3)Xwith triple-decker structures (L-Ph= 2,5-di(o-pyridyl)-3,4-diphenylpyrrolate; X = Cl, AlCl4, OTf, and PF6) was synthesized by reducingL(Ph)SnClwith (LiBBu3H)-Bu-s and subsequent reactions. Structural characterization of((LSn)-Sn-Ph)(3)Clrevealed a Sn-Sn-Sn core, and DFT calculations suggest that its HOMO is primarily sigma-bonding along the tri-tin framework.((LSn)-Sn-Ph)(3)Clreacts with W(CO)(5)THF to afford((LSn)-Sn-Ph)(2)(W(CO)(5))(2)andL(Ph)SnCl, implying that((LSn)-Sn-Ph)(3)Clmay exhibit dynamic behavior in solution.
CONY: A Bayesian procedure for detecting copy number variations from sequencing read depths
(2020-06-26)
Wei, Yu-Chung
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Huang, Guan-Hua
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統計學研究所
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Institute of Statistics
Copy number variations (CNVs) are genomic structural mutations consisting of abnormal numbers of fragment copies. Next-generation sequencing of read-depth signals mirrors these variants. Some tools used to predict CNVs by depth have been published, but most of these tools can be applied to only a specific data type due to modeling limitations. We develop a tool for copy number variation detection by a Bayesian procedure, i.e., CONY, that adopts a Bayesian hierarchical model and an efficient reversible-jump Markov chain Monte Carlo inference algorithm for whole genome sequencing of read-depth data. CONY can be applied not only to individual samples for estimating the absolute number of copies but also to case-control pairs for detecting patient-specific variations. We evaluate the performance of CONY and compare CONY with competing approaches through simulations and by using experimental data from the 1000 Genomes Project. CONY outperforms the other methods in terms of accuracy in both single-sample and paired-samples analyses. In addition, CONY performs well regardless of whether the data coverage is high or low. CONY is useful for detecting both absolute and relative CNVs from read-depth data sequences. The package is available at https://github.com/weiyuchung/CONY.
Graphene-Loaded Plasmonic Zirconium Nitride and Gold Nanogroove Arrays for Surface-Charge Modifications
(2020-06-26)
Yu, Min-Wen
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Ishii, Satoshi
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Ku, Ji-Ren
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Yang, Jhen-Hong
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Huang, Chih-Hsiang
Graphene-on-metal (G/M) heterostructures have gained considerable attention in recent years owing to their outstanding optical and electrical properties. In this study, the polarity of graphene doping to different metallic materials underneath graphene is analyzed for applications in surface-charge modifications. Kelvin probe force microscopy clearly reveals the charge-transfer effects of plasmonic zirconium nitride (ZrN) and gold (Au) on the formation of G/M heterostructures. In addition, both ZrN and Au nanogroove arrays are fabricated by focused ion beam to generate surface plasmon resonances. The charge-transfer effects influence the effective permittivities of ZrN and Au surfaces such that opposite plasmonic resonance shifts are demonstrated for the ZrN and Au nanogroove arrays. Our results show that the choice of metallic material is important for achieving a desired charge transfer in the loading of graphene onto metallic materials.
Highly hydrophobic metal-organic framework for self-protecting gate dielectrics
(2020-06-28)
Inamdar, Arif I.
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Pathak, Abhishek
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Usman, Muhammad
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Chiou, Kuan-Ru
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Tsai, Pei-Hsien
A hydrophobic metal-organic framework (MOF) showing high-kappa behaviour was synthesized by the reaction of copper ions with 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (HFDPA). The unique, highly hydrophobic nature of the material protects it from re-adsorbing water, even in a high humidity environment. The dielectric constant of the MOF showed an unprecedented increasing trend, reaching up to kappa approximate to 99 at 300 K and 1 kHz after the complete removal of guest and coordinated water molecules. The unusual dielectric behaviour of the compound along with its water resistant properties is the first report of such behaviour and it paves the way for the development of moisture-stable microelectronic devices.
2-Dimensional cross-shaped tetrathienonaphthalene-based ladder-type acceptor for high-efficiency organic solar cells
(2020-06-28)
Chang, Shao-Ling
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Cao, Fong-Yi
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Huang, Kuo-Hsiu
;
Lee, Wei-Liang
;
Lee, Meng-Hsun
AnNC-FICnonfullerene acceptor, using a didodecylnaphthodithiophene (NDT) embedded octacyclic ladder-type donorNC, had been described previously. In this work, a new cross-shapedTC-FICnonfullerene acceptor is designed by substitution of the NDT unit in theNCskeleton with a 2-dimensional didodecyltetrathienonaphthalene (TTN) unit. The 2-dimensionalTC pi-system with two vertically fused thiophenes strengthens the electron-donating ability, promotes pi-electron delocalization and enhances intramolecular donor-acceptor charge transfer and intermolecular pi-pi interactions. As a result,TC-FICshows more red-shifted and widened absorption compared to theNC-FICcounterpart. The PBDB-T:TC-FICdevice exhibits a higher efficiency of 11.6% which greatly outperformed the corresponding PBDB-T:NC-FICdevice with an efficiency of 7.52%. The dramatic 54% enhancement in efficiency is ascribed to the improved light-harvesting ability and enhanced charge mobilities which are benefited from the central 2-dimensionalTTNmoiety. By incorporatingPC(71)BMto improve absorption and electron transport, the ternary-blend PBDB-T : TC-FIC : PC(71)BMdevice (1 : 1 : 1 in wt%) achieves a highest PCE of 13.49% with an enhancedJ(sc)of 23.80 mA cm(-2), an FF of 64.4%, and aV(oc)of 0.88 V.