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Chlorinated 2,1,3-Benzothiadiazole-Based Polymers for Organic Field-Effect Transistors
Kang, So-Huei,Tabi, Grace Dansoa,Lee, Junghoon,Kim, Gyoungsik,Noh, Yong-Young,Yang, Changduk American Chemical Society 2017 Macromolecules Vol.50 No.12
<P>The vital role of introducing chlorine (Cl) atoms onto conjugated polymers, which affects their semiconducting properties, is not yet well understood. A series of donoracceptor polymers based on dichlorinated-2,1,3-benzothiadiazole (2ClBT) and four different donor moieties with various conjugation lengths (thiophene (T), thieno[3,2-b]thiophene (TT), 2,2'-bithiophene (DT), and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT)) were synthesized and used in organic field-effect transistors (OFETs). The structureproperty relationship associated with the 2ClBT-based polymers was thoroughly investigated via a range of techniques, and it was found that a change in the conjugation length of the main backbone could alter energy levels, morphology, and optoelectronic properties, which had a significant effect on the charge transport property. P2CLBT-TVT exhibited superior qualities relative to the other samples with respect to the degree of uniform film-forming ability and molecular organization and charge carrier transport, which resulted in the best hole mobility of 0.147 cm(2) V-1 s(1). Furthermore, we also emphasize that for all the polymers no substantial changes were observed in the OFET transfer-curve slopes during 200 testing cycles, indicating excellent operational stability. This study demonstrates that the design of semiconducting polymers possessing Cl atoms was effective at improving operating stability in the OFETs manufactured from them.</P>
Kang, So-Huei,Lee, Hae Rang,Dutta, Gitish K.,Lee, Junghoon,Oh, Joon Hak,Yang, Changduk American Chemical Society 2017 Macromolecules Vol.50 No.3
<P>The pi-extended (E)-2-(2-(thiophen-2-ye-vinyl)thiophene (TVT)-based polymers are an interesting class of semiconducting polymers because of their excellent mobilities and unique film microstructures. Despite these properties, the effect of the side-chain regiochemistry of TVT skeletons on the intrinsic properties of these polymers remains unclear. To investigate this, in this study, hexyl-substituted TVT subunits with a 'tail in (TI)' or 'tail out (TO)' regiosymmetrical arrangement were first introduced into diketo-pyrrolopyrrole (DPP) -based copolymer main chains to afford 'isomeric' polymers PI and PO, respectively. By combining optical spectroscopy, atomic force microscopy (AFM), and grazing incidence X-ray diffraction (GIXD) data, we quantitatively characterized the aggregation, crystallization, and backbone orientation of both polymer films, which were then correlated to the charge carrier mobilities. The PI film exhibited a bimodal packing motif comprising a mixture of edge-on and face-on orientations, which was beneficial for three-dimensional (3D) charge transport and resulted in a hole mobility 2-fold larger than that in the PO film (mu(h) = 1.69 cm(2) V-1 s(-1)). This comparative study substantiates the important role of the regiochemistry of TVT in developing high-performance semiconducting polymers.</P>
Kumari, Tanya,Moon, Mijin,Kang, So-Huei,Yang, Changduk Elsevier 2016 Nano energy Vol.24 No.-
<P><B>Abstract</B></P> <P>In order to address the question of how macromolecular additive processing in recent years, sparsely used, affects structural organization and photovoltaic performance, various macromolecular additives (PS, PDMS, and PMMA) vis-à-vis small DIO additive are applied to a model bulk-heterojunction (BHJ) system based on DTGe(FBTTh<SUB>2</SUB>)<SUB>2</SUB>. These additives have been shown to exhibit a strong influence on film morphology as a function of additives type, with significant changes in packing orientation, film roughness, and feature size observed, leading to improved power-conversion efficiency (PCE). Interestingly, an unexpectedly large increase in PCEs, from 6.03% to 7.07%, is demonstrated upon adding 1% (w/w) PMMA to DTGe(FBTTh<SUB>2</SUB>)<SUB>2</SUB>:PC<SUB>61</SUB>BM devices, possessing an even greater PCE than DIO. In addition, when 0.2% (v/v) DIO is added to DTGe(FBTTh<SUB>2</SUB>)<SUB>2</SUB>:PC<SUB>71</SUB>BM, several key device metrics increase, producing the highest PCE of 7.55% for DTGe(FBTTh<SUB>2</SUB>)<SUB>2</SUB>-based devices to date. In the present work, PMMA is confirmed to provide a highly effective means for controlling morphology and significantly enhancing PCEs. Not only do the results from this study will aid in understanding the mechanisms underlying the impact of macromolecular additive processing, but they will also be key in leading to future studies that will elucidate the driving forces behind and exact points of interaction of macromolecular additives.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effects of various macromolecular additives on OPV performance are investigated. </LI> <LI> Introducing PMMA in DTGe(FBTTh2)2:PC61BM can bring 17% improvement in the efficiency. </LI> <LI> The efficiency up to 7.55% in DIO-treated DTGe(FBTTh2)2:PC71BM films is achieved. </LI> <LI> Our study aids in understanding the mechanisms of the macromolecular additives. </LI> <LI> PMMA utility should be applicable to various other organic solar systems. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kumar, Sujit,Choi, Yunseong,Kang, So-Huei,Oh, Nam Khen,Lee, Junghyun,Seo, Jihyung,Jeong, Mingyu,Kwon, Hyoung Woo,Seok, Sang Il,Yang, Changduk,Park, Hyesung American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.42
<P>Significant research efforts are currently being devoted to improving both the crystalline quality and stability of lead halide perovskite absorbers to advance the commercial prospects of perovskite-based solar cells. Herein, we report a simple one-step dibutylhydroxytoluene (BHT) additive-based approach for simultaneously improving the crystallinity and resistance of perovskite films under adverse degradation conditions. We found that BHT, commonly known for its antioxidant properties, can considerably improve the performance of methylammonium lead iodide perovskite solar cells by modulating the chemical environment within the precursor medium to form intermediate complexes, and it can also suppress photooxidation, which results in perovskite degradation under environmental operating conditions. Consequently, a device exhibited a significant power conversion efficiency improvement to 18.1% with the BHT-additive-based perovskite absorber, exceeding the 17.1% efficiency achieved for the control device. The BHT additive also improved the perovskite stability by quenching intermediate reactions resulting in perovskite degradation to an undesirable lead iodide phase, as evidenced by detailed analysis of absorption spectra, grazing-incidence wide-angle X-ray scattering, X-ray photoelectron spectra, and photoluminescence measurements.</P> [FIG OMISSION]</BR>
Dereje, Mamo Melaku,Ji, Dongseob,Kang, So-Huei,Yang, Changduk,Noh, Yong-Young Applied Science Publishers 2017 Dyes and pigments Vol.145 No.-
<P><B>Abstract</B></P> <P>In this work, we investigate the effect of pre-aggregated solutions of diketopyrrolopyrrole (DPP)-based conjugated polymers to achieve highly-aligned polymer films for high-performance organic field-effect transistors (OFETs). A suitable marginal solvent is selected for 5-octyl-pentadecyl branched DPP and selenophene-based semiconducting polymer (PDPP(SE)-ε-C<SUB>8</SUB>C<SUB>15</SUB>) by utilizing the Hansen solubility parameter calculation. The anisotropic one-dimensional aligned PDPP(SE)-ε-C<SUB>8</SUB>C<SUB>15</SUB> film was off-center spin-coated from the pre-aggregated solution is studied by atomic force microscopy and polarized UV-Vis absorption spectroscopy. A significantly high hole mobility of 4.16 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP> was achieved from the OFETs with a unidirectionally-aligned PDPP(SE)-ε-C<SUB>8</SUB>C<SUB>15</SUB> film to the transistor channel direction.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Selection of suitable solvent for preparing pre-aggregated solutions of polymers. </LI> <LI> Formation of anisotropic thin films from the pre-aggregated polymer solutions. </LI> <LI> Directionally aligned polymer films differ in property and their FET performances. </LI> <LI> Thin films aligned parallel to the transistor channel direction show high mobility. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Lee, Kyu Cheol,Lee, Hae Rang,Kang, So-Huei,Lee, Jungho,Park, Young IL,Noh, Seung Man,Oh, Joon Hak,Yang, Changduk Royal Society of Chemistry 2018 Polymer chemistry Vol.9 No.42
<P> Despite having unique structural features, e.g., high co-planarity and a strong polar bicyclic lactam structure, thiophene bipyrrolylidene-2,2’(1H,1’H)-dione (TBPD) has been less explored as a dye, mainly due to the quite low yield in its synthesis via lactone-to-lactam conversion. We reported an efficient methodology for synthesizing TBPD in high yield using p-toluenesulfonic acid monohydrate and a catalytic amount of 4-dimethylaminopyridine in the chloroform solvent. From the newly synthesized series of TBPD-based donor?acceptor-type polymers, we fabricated organic field-effect transistors (OFETs), which were subjected to a systematic study on the relationship between film microstructure and charge transport. Among them, the annealed PTBPD-Th film revealed a more ordered lamellar packing with the highest number of interlayers and preferential edge-on orientation, yielding the best hole mobility (up to 0.46 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>). The improved synthesis of TBPD and our findings concerning related polymers could promote further research and development associated with the TBPD unit. </P>
Kumari, Tanya,Lee, Sang Myeon,Kang, So-Huei,Chen, Shanshan,Yang, Changduk Royal Society of Chemistry 2017 ENERGY AND ENVIRONMENTAL SCIENCE Vol.10 No.1
<P>Ternary organic solar cells (OSCs), with a simple structure, can be easily adopted as sub-cells in a tandem design, thereby further enhancing the power conversion efficiency (PCE). Considering the potential to surpass the theoretical PCE limit in OSCs, we incorporated a benzo[1,2-<I>b</I>;4,5-<I>b</I>′]dithiophene-based small molecule into a poly(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-<I>b</I>;4,5-<I>b</I>′]dithiophene-2,6-diyl-<I>alt</I>-(4-(2-ethylhexyl)-3-fluorothieno[3,4-<I>b</I>]thiophene-)-2-carboxylate-2-6-diyl):[6,6]-phenyl-C71-butyric acid methyl ester host system. A hitherto unrealized PCE of 12.1% was achieved at the optimized composition of the ternary blend. The ternary blend surprisingly had a face-on and edge-on co-existent texture, which is far better than that of the face-on orientated host film. To the best of our knowledge, this intriguing result refutes for the first time a general paradigm that high-performance OSCs are unambiguously linked to face-on structures. Therefore, our study provides a new platform for refining the theoretical underpinning of multiple blending OSCs.</P>