Browsing by Author "Huang, Chi-Feng"

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Flat-on ambipolar triphenylamine/C-60 nano-stacks formed from the self-organization of a pyramid-sphere-shaped amphiphile
(2016-01-01)
Liang, Wei-Wei
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Huang, Chi-Feng
;
Wu, Kuan-Yi
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Wu, San-Lien
;
Chang, Shu-Ting
A giant amphiphile, which is constructed with an amorphous nano-pyramid (triphenylamine, TPA) and a crystalline nano-sphere (C-60), was synthesized. Structural characterization indicates that this pyramid-sphere-shaped amphiphile (TPA-C-60) forms a solvent-induced ordered phase, in which the two constituent units self-assemble into alternating stacks of two-dimensional (2D) TPA and C-60 nanosheets. Due to the complexity of the molecular structure and the amorphous nature of the nano-pyramid, phase formation was driven by intermolecular C-60-C-60 interactions and the ordered phase could not be reformed from the TPA-C-60 melt. Oriented crystal arrays of TPA-C-60, which contain flaton TPA/C-60 nano-stacks, can be obtained via a PDMS-assisted crystallization (PAC) technique. The flaton dual-channel supramolecular structure of TPA-C-60 delivered ambipolar and balanced charge-transport characteristics with an average me of 2.11 x 10(-4) cm(2) V-1 s(-1) and mh of 3.37 x 10(-4) cm(2) V-1 s(-1). The anisotropic charge-transport ability of the pyramid-sphere-shaped amphiphile was further understood based on the lattice structure and the lattice orientation of TPA-C-60 revealed from electron diffraction analyses.
Packing Principles for Donor-Acceptor Oligomers from Analysis of Single Crystals
(2016-08-09)
Huang, Chi-Feng
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Wu, San-Lien
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Huang, Yi-Fan
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Chen, Ying-Chen
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Chang, Shu-Ting
D-A conjugated molecules are complicated in both their molecular and their packing structures. In this perspective, we summarize more than 40 crystal lattices of conjugated oligomers to identify the morphological influence of each building block on the D-A molecules. These lattice structures reveal not only the packing preferences of the conjugated oligomers but also the conformational disorder in the lattices. The presence of this disorder in slowly grown crystals implies that attaining total long-range conformational order is challenging for D-A oligomers, which are structurally complicated and readily distorted and which have building blocks of incommensurate packing dimensions. In optoelectronic applications, a decreased duration of processing can prevent ordering and trap the thin films of D-A oligomers from becoming crystalline phases. Although D-A oligomers conform to packing principles in the formation of a single crystal, their phase behaviors in the formation of active thin films are much more difficult to comprehend. Continuous advances in methods of characterization are still strongly required for the steps of attaining a true structure property relation of D-A oligomers in active films for optoelectronic applications.
Polymorphisms and morphological studies of a difluorobenzothiadiazole conjugated copolymer with 7.8% polymer solar cell efficiency
(2015-01-01)
Huang, Chi-Feng
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Chang, Jen-Yun
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Huang, Sin-Hong
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Wu, Kuan-Yi
;
Jheng, Jyun-Fong
This study presents the structural characterization of a 5,6-difluorobenzo- 2,1,3-thiadiazole (FBT)-quaterthiophene (Th-4) alternating copolymer (PTh4FBT) and how the crystalline nature of PTh4FBT affects the PTh4FBT-PC71BM morphology and the device performances. The single crystal structure of 5,6-difluoro-4,7-di(thiophen-2-yl) benzothiadiazole (Th2FBT) first confirms the low conformational preference of the FBT containing molecule. Since the crystallization process does not assist in unifying the conformation of Th2FBT, both intrachain conformation and interchain c-shifts in the crystalline state of PTh4FBT have to be scrutinized. By comparing the 2D WAXS pattern of PTh4FBT and the simulated patterns generated from Cerius(2) molecular modeling, it was found that the diffraction pattern generated from the lattice containing PTh4FBT with anti-conformation and limited interchain c-shift matches best with the experimental one. The face-to-face interchain stacking of PTh4FBT rendered strong crystalline nature to the polymer and caused large segregation in the PTh4FBT-PC71BM blend system, which was indicated by the TEM and GI WAXS morphological studies. The aggregation size was reduced via the use of the 1-chloronaphthalene additive. The optimized morphology led to improved J(sc) and FF. The single-junction PTh4FBT-PC71BM based polymer solar cells deliver a high PCE of 7.75% with a V-oc of 0.76 V, a J(sc) of 14.36 mA cm(-2), and a FF of 71.0%.
Role of Tin Chloride in Tin-Rich Mixed-Halide Perovskites Applied as Mesoscopic Solar Cells with a Carbon Counter Electrode
(2016-12)
Tsai, Cheng-Min
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Wu, Hui-Ping
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Chang, Sun-Tang
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Huang, Chi-Feng
;
Wang, Chia-Hsin
We report the synthesis and characterization of alloyed Sn Pb methylammonium mixed-halide perovskites (CH3NH3SnyPb1-yI3-xClx) to extend light harvesting toward the near infrared region for carbon-based mesoscopic solar cells free of organic hole-transport layers. The proportions of Sn in perovskites are well controlled by mixing tin chloride (SnCl2) and lead iodide (Pbl(2)) in varied stoichiometric ratios (y = 0-1). SnCl2 plays a key role in modifying the lattice structure of the perovskite, showing anomalous optical and optoelectronic properties; upon increasing the concentration of SnC2, the variation of the band gap and band energy differed from those of the Snl(2) precursor. The CH3NH3SnyPb1-yI3-xClx devices showed enhanced photovoltaic performance upon increasing the proportion of SnCl2 until y = 0.75, consistent with the corresponding potential energy levels. The photovoltaic performance was further improved upon adding 30 mol % tin fluoride (SnF2) with device configuration FTO/TiO2/Al2O3/NiO/C, producing the best power conversion efficiency, 5.13%, with great reproducibility and intrinsic stability.
Stepwise Structural Evolution of a DTS-F2BT Oligomer and Influence of Structural Disorder on Organic Field Effect Transistors and Organic Photovoltaic Performance
(2016-12-27)
Huang, Chi-Feng
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Huang, Sin-Hong
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Hsieh, Chou-Ting
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Chao, Yi-Hsiang
;
Li, Chia-Hua
An A-D-A oligomer, DTS(F2BT)(2), was synthesized; its structural evolution was studied with DSC, POM, 2D-WAXD, and in-situ GI-XRD. The structural evolution of DTS(F2BT)(2) is stepwise and kinetically slow. Both rapid drying and the presence of PC71BM trapped DTS(F2BT)(2) in a less ordered nematic (N) phase. PDMS-assisted crystallization enabled a pristine DTS(F2BT)(2) thin film to attain a more ordered equilibrium phase, and enhanced the OFET mobility of DTS(F2BT)(2). In OPV devices, DIO additive drove the DTS(F2BT)(2) domains in the DTS(F2BT)(2):PC71BM blended film from the N phase toward the equilibrium phase, and resulted in enhanced OPV performances. These results reveal the slow ordering process of the A-D-A oligomer, and the importance of monitoring the degree of structural evolution of the active thin films in organic optoelectronics.