Browsing by Author "Sahu, Duryodhan"

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Enhancement of photovoltaic properties in supramolecular polymer networks featuring a solar cell main-chain polymer H-bonded with conjugated cross-linkers
(2012-03-09)
Patra, Dhananjaya
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Ramesh, Mohan
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Sahu, Duryodhan
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Padhy, Harihara
;
Chu, Chih-Wei
Stille polymerization was employed to synthesize a low-band-gap (LOG) conjugated main-chain polymer PBTH consisting of bithiazole, dithieno[3,2-b:2',3'-d]pyrroles (DTP), and pendent melamine derivatives. Novel supramolecular polymer networks PBTH/C and PBTH/F were developed by mixing proper molar amounts of polymer PBTH (containing melamine pendants) to be hydrogen-bonded (H-bonded) with complementary uracil-based conjugated cross-linkers C and F (i.e., containing two symmetrical uracil moieties connected with carbazole and fluorene units through triple bonds). The formation of multiple H-bonds between polymer PBTH and cross-linkers C or F was confirmed by FT-IR measurements. In contrast to polymer PBTH, the supramolecular design with multiple H-bonds can enhance the photovoltaic properties of polymer solar cell (PSC) devices containing H-bonded polymer networks PBTH/C and PBTH/F by tuning their light harvesting capabilities, HOMO energy levels, and crystallinities. Initially, the power conversion efficiency (PCE) values of PSC devices containing supramolecular polymer networks PBTH/C and PBTH/F as electron donors and [6,6]-phenyl-C-71-butyric acid methyl ester (PC70BM) as an electron acceptor (polymer:PC70BM = 1:1 w/w) are found to be 0.97 and 0.68%, respectively, in contrast to 0.52% for polymer PBTH. The highest PCE value of 1.56% with a short-circuit current densities (J(sc)) value of 7.16 mA/cm(2), a open circuit voltages (V-oc) value of 0.60 V. and a fill factor (FF) of 0.36 was further optimized in the PSC device containing a supramolecular polymer network PBTH/C as polymer:PC70BM = 1:2 w/w. These results indicate that supramolecular design is an effective route towards better photovoltaic properties of V-oc, J(sc), and PCE values in polymer solar cells. (C) 2012 Elsevier Ltd. All rights reserved.
Fine Tuning of HOMO Energy Levels for Low-Band-Gap Photovoltaic Copolymers Containing Cyclopentadithienopyrrole and Bithiazole Units
(2011-09-15)
Patra, Dhananjaya
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Sahu, Duryodhan
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Padhy, Harihara
;
Kekuda, Dhananjay
;
Chu, Chih-Wei
Five conjugated LBG polymers P1-P5 consisting of a DTP unit as an electron donor and various bithiazole units as electron acceptors are designed and synthesized for photovoltaic applications. The effects of the electron-deficient bithiazole derivatives on the thermal, optical, electrochemical, and photovoltaic properties are investigated. The molecular structures are confirmed and characterized. The resulting polymers have high thermal stabilities and broad absorption bands with low optical bandgaps. The hole and electron mobilities are calculated. PSC devices are fabricated utilizing the polymers as electron donors and PCBM as an electron acceptor. The PSC device with an active layer of P4:PCBM (1:1 by weight) exhibits the best power-conversion efficiency.
Structural planarity and conjugation effects of novel symmetrical acceptor-donor-acceptor organic sensitizers on dye-sensitized solar cells
(2012-04-01)
Chu, Hsuan-Chih
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Sahu, Duryodhan
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Hsu, Ying-Chan
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Padhy, Harihara
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Patra, Dhananjaya
In this study two series of novel symmetrical acceptor-donor-acceptor organic sensitizers containing 3,6- and 2,7-functionalized carbazole cores, respectively, connected to two anchoring cyanoacrylic acid termini via thienyl linkers were synthesized. The effect of the molecular planarity originating from the 3,6- and 2,7-functionalized carbazole cores on the performance of corresponding solar cells were investigated. Molecular orbital analyses revealed the characteristics of the carbazole-based highest occupied molecular orbitals and acid-based lowest unoccupied molecular orbitals. Time-dependent density functional theory calculations allowed us to assign the electronic transitions (>90%) of the low energy bands. Among these new dyes, the highest power conversion efficiency of 4.82% was obtained in a dye-sensitized solar cell device under standard AM 1.5 sunlight with an open-circuit voltage of 0.61 V, a short-circuit photocurrent density of 12.66 mA cm(-2) and a fill factor of 0.62. (C) 2011 Elsevier Ltd. All rights reserved.
Study of Supramolecular Side-Chain Copolymers Containing Light-Emitting H-Acceptors and Electron-Transporting Dendritic H-Donors
(2008-12-23)
Yang, Po-Jen
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Wu, Chung-Wen
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Sahu, Duryodhan
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Lin, Hong-Cheu
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材料科學與工程學系
A novel light-emitting hydrogen-bonded (H-) acceptor PBB (M1) containing three conjugated aromatic rings, including one pyridyl terminus and two lateral methoxyl groups (on the middle ring), was successfully synthesized via Horner-Wadsworth-Emmons (HWE) olefination and Sonogashira coupling reaction. Moreover, different molar ratios of light-emitting H-acceptor monomer PBB (MI) and hole-transporting monomer CAZ (M2) bearing a carbazole unit were copolymerized through free radical polymerization to obtain light-emitting and hole-transporting H-acceptor copolymers (P1-P5). H-acceptor copolymers P3 and P4 were complexed with different generations of dendritic H-donors (G1COOH-G3COOH) bearing 1,3,4-oxadiazole (OXD) dendrons and terminal benzoic acids via H-bonded self-assembly to form supramolecular side-chain copolymers (i.e., H-bonded dendritic complexes). In contrast to H-acceptor homopolymer P1(HPBB), H-acceptor copolymers P2-P4 incorporated with carbazole (CAZ) moieties effectively enhance the glass transition temperatures (T(g)s) and minimize the interchain interations of the light-emitting H-acceptor units, and similar effects occur in their H-bonded dendritic complexes. In addition, red shifts of photoluminescence (PL) emissions in H-bonded dendritic complexes can be tuned up to 61 nm. Furthermore, H-bonded dendritic complexes excited at 305 nm of OXD absorption can create a stronger fluorescence than that excited at 397 nm of PBB absorption, indicating that the intensity of the sensitized emission of PBB (by energy transfer from OXD absorption at 305 nm) is even stronger than that of a direct emission of PBB (by merely PBB absorption at 397 nm). The OXD dendritic wedges in H-bonded dendritic complexes can lower the LUMO energy levels and provide a better electron injection property. H-acceptor polymer P4 and its H-bonded dendritic complexes showed electroluminescence (EL) emissions in the range of 464-519 nm from blue to green. In addition, a PLED device containing H-bonded dendritic complex P4/G1COOH showed an EL emission of 519 nm under a turn-on voltage of 6.5 V. with a maximum luminance of 408 cd/m(2) at 18 V and a luminance efficiency of 0.39 cd/A at 100 mA/cm(2), respectively.
Surface Modification of Gold Nanorods by Grafting Fluorene-Based Conjugated Copolymers Containing Thiol-Pendants
(1970-01-01)
Sahu, Duryodhan
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Chu, Hsuan-Chih
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Yang, Po-Jen
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Lin, Hong-Cheu
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材料科學與工程學系
"Two conjugated surfactants of monomer TF and polymer PTF with pendant thiol groups are synthesized for surface modifications of gold nanorods (GNRs). Cetyltrimethylammonium bromide (CTAB)-GNRs (without surface-modification) in aqueous solutions are prepared, and the original CTAB surfactant is replaced with TF and PTF due to their thiol-gold grafting reactions. Surface-modified TF-GNRs and PTF-GNRs in THF are obtained. UV-visible spectra provide the grafting evidence of TF and PTF. Compared with TF-GNRs, the PTF-GNRs show better solubility and stability against aggregations of nanorods in THF. TEM and XPS confirm the existence of binding bonds between the sulfur groups of PTF and the gold surface in PTF-GNRs. Compared with polymer surfactant (PTF), the faster PL emission decay in PTF-GNRs match well with the PL quenching of PTF-GNRs. Surface modifications are verified by UV-visible, TEM, XPS, PL and lifetime measurements."
Synthesis and application of H-Bonded cross-linking polymers containing a conjugated pyridyl H-Acceptor side-chain polymer and various carbazole-based H-Donor dyes bearing symmetrical cyanoacrylic acids for organic solar cells
(2010-12-10)
Sahu, Duryodhan
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Padhy, Harihara
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Patra, Dhananjaya
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Kekuda, Dhananjay
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Chu, Chih-Wei
A series of novel hydrogen-bonded (H-bonded) cross-linking polymers were generated by complexing various proton-donor (H-donor) solar cell dyes containing 3,6- and 2,7-functionalized electron-donating carbazole cores bearing symmetrical thiophene linkers and cyanoacrylic acid termini with a proton-acceptor (H-acceptor) side-chain homopolymer carrying pyridyl pendants (with 1/2 M ratio of H-donor/H-acceptor). The supramolecular H-bonded structures between H-donor dyes and the H-acceptor side-chain polymer were confirmed by FTIR measurements. The effects of the supramolecular architecture on optical, electrochemical, and organic photovoltaic (OPV) properties were investigated. From DFT (density functional theory) calculations, the optimized geometries of organic dyes reflected that the carbazole cores of H-donor dyes were coplanar with the conjugated thiophenes and cyanoacrylic acids, which is essential for strong conjugations across the donor-acceptor units in D1-D4 dyes. Under 100 mW/cm(2) of AM 1.5 white-light illumination, bulk heterojunction (BHJ) OPV cell devices containing an active layer of H-bonded polymers (PDETP/D1-D4) as an electron donor blended with [6,6]-phenyl C(61)-butyric acid methyl ester (PCBM) as an electron acceptor in a weight ratio of 1:1 were explored. From the preliminary investigations, the OPV device containing 1:1 weight ratio of H-bonded polymer PDFTP/D2 and PCBM showed the best power conversion efficiency (PCE) value of 0.31% with a short-circuit current (J(sc)) of 1.9 mA/cm(2), an open-circuit voltage (V(oc)) of 0.55 V. and a fill factor (FF) of 29%, which has a higher PCE value than the corresponding H-donor D2 dye (PCE = 0.15%) or H-acceptor PDFTP homopolymer (PCE = 0.02%) blended with PCBM in 1:1 weight ratio. (C) 2010 Elsevier Ltd. All rights reserved.
Synthesis and Applications of 2,7-Carbazole-Based Conjugated Main-Chain Copolymers Containing Electron Deficient Bithiazole Units for Organic Solar Cells
(2010-12-01)
Patra, Dhananjaya
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Sahu, Duryodhan
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Padhy, Harihara
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Kekuda, Dhananjay
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Chu, Chih-Wei
A series of low-band-gap (LBG) donor-accepor conjugated main-chain copolymers (P1-P4) containing planar 2,7-carbazole as electron donors and bithiazole units (4,4'-dihexyl-2,2'-bithiazole and 4,4'-dihexyl-5,5'-di(thiophen-2-yl)-2,2'-bithiazole) as electron acceptors were synthesized and studied for the applications in bulk heterojunction (BHJ) solar cells. The effects of electron deficient bithiazole units on the thermal, optical, electrochemical, and photovoltaic (PV) properties of these LBG copolymers were investigated. Absorption spectra revealed that polymers P1-P4 exhibited broad absorption bands in UV and visible regions from 300 to 600 nm with optical band gaps in the range of 1.93-1.99 eV, which overlapped with the major region of the solar emission spectrum. Moreover, carbazole-based polymers P1-P4 showed low values of the highest occupied molecular orbital (HOMO) levels, which provided good air stability and high open circuit voltages (V(oc)) in the PV applications. The BHJ PV devices were fabricated using polymers P1-P4 as electron donors and (6,6)-phenyl-C(61)-butyric acid methyl ester (PC(61)BM) or (6,6)-phenyl-C(71)-butyric acid methyl ester (PC(71)BM) as electron acceptors in different weight ratios. The PV device bearing an active layer of polymer blend P4:PC(71)BM (1:1.5 w/w) showed the best power conversion efficiency value of 1.01% with a short circuit current density (J(sc)) of 4.83 mA/cm(2), a fill factor (FF) of 35%, and V(oc) - 0.60 V under 100 mW/cm(2) of AM 1.5 white-light illumination. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5479-5489, 2010
Synthesis and applications of a novel supramolecular polymer network with multiple H-bonded melamine pendants and uracil crosslinkers
(2012-03-01)
Patra, Dhananjaya
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Ramesh, Mohan
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Sahu, Duryodhan
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Padhy, Harihara
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Chu, Chih-Wei
A conjugated main-chain copolymer (PBT) consisting of bithiazole, dithieno[3,2-b:2',3'-d]pyrroles (DTP), and pendent melamine units was synthesized by Stille polymerization, which can be hydrogen-bonded (H-bonded) with proper molar amounts of bi-functional p-conjugated crosslinker F (i.e., two uracil motifs covalently attached to a fluorene core through triple bonds symmetrically) to develop a novel supramolecular polymer network (PBT/F). The effects of multiple H-bonds on light harvesting capabilities, HOMO levels, and photovoltaic properties of polymer PBT and H-bonded polymer network PBT/F are investigated. The formation of supramolecular polymer network (PBT/F) between PBT and F was confirmed by FTIR and XRD measurements. Because of the stronger light absorption, lower HOMO level, and higher crystallinity of H-bonded polymer network PBT/F, the solar cell device containing PBT/F showed better photovoltaic properties than that containing polymer PBT. The preliminary results show that the solar cell device containing 1:1 weight ratio of PBT/F and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) offers the best power conversion efficiency (PCE) value of 0.86% with a short-circuit current density (Jsc) of 4.97 mA/cm2, an open circuit voltage (Voc) of 0.55 V, and a fill factor (FF) of 31.5%. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Synthesis and Applications of Cyano-Vinylene-Based Polymers Containing Cyclopentadithiophene and Dithienosilole Units for Photovoltaic Cells
(2011-08-01)
Padhy, Harihara
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Sahu, Duryodhan
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Patra, Dhananjaya
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Pola, Murali Krishna
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Huang, Jen-Hsien
Two beta-cyano-thiophenevinylene-based polymers containing cyclopentadithiophene (CPDT-CN) and dithienosilole (DTS-CN) units were synthesized via Stille coupling reaction with Pd(PPh(3))(4) as a catalyst. The effects of the bridged atoms (C and Si) and cyano-vinylene groups on their thermal, optical, electrochemical, charge transporting, and photovoltaic properties were investigated. Both polymers possessed the highest occupied molecular orbital (HOMO) levels of about -5.30 eV and the lowest unoccupied molecular orbital (LUMO) levels of about -3.60 eV, and covered broad absorption ranges with narrow optical band gaps (ca. 1.6 eV). The bulk heterojunction polymer solar cell (PSC) devices containing an active layer of electron-donor polymers (CPDT-CN and DTS-CN) blended with an electron-acceptor, that is, [6,6]-phenyl-C(61)-butyric acid methyl ester (PC(61)BM) or [6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM), in different weight ratios were explored under 100 mW/cm(2) of AM 1.5 white-light illumination. The PSC device based on DTS-CN:PC(71)BM (1:2 w/w) exhibited a best power conversion efficiency (PCE) value of 2.25% with V(oc) = 0.74 V, J(sc) = 8.39 mA/cm(2), and FF = 0.36. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 3417-3425, 2011
Synthesis and Applications of Low-Bandgap Conjugated Polymers Containing Phenothiazine Donor and Various Benzodiazole Acceptors for Polymer Solar Cells
(2010-11-01)
Padhy, Harihara
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Huang, Jen-Hsien
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Sahu, Duryodhan
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Patra, Dhananjaya
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Kekuda, Dhananjay
A series of soluble donor-acceptor conjugated polymers comprising of phenothiazine donor and various benzodiazole acceptors (i.e., benzothiadiazole, benzoselenodiazole, and benzoxadiazole) sandwiched between hexyl-thiophene linkers were designed, synthesized, and used for the fabrication of polymer solar cells (PSC). The effects of the benzodiazole acceptors on the thermal, optical, electrochemical, and photovoltaic properties of these low-bandgap (LBG) polymers were investigated. These LBG polymers possessed large molecular weight (M(n)) in the range of 3.85-5.13 x 10(4) with high thermal decomposition temperatures, which demonstrated broad absorption in the region of 300-750 nm with optical bandgaps of 1.80-1.93 eV. Both the HOMO energy level (-5.38 to -5.47 eV) and LUMO energy level (-3.47 to -3.60 eV) of the LBG polymers were within the desirable range of ideal energy level. Under 100 mW/cm(2) of AM 1.5 white-light illumination, bulk heterojunction PSC devices containing an active layer of electron donor polymers mixed with electron acceptor [6,6]-phenyl-C(61)-butyric acid methyl ester (PC(61)BM) or [6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM) in different weight ratios were investigated. The best performance of the PSC device was obtained by using polymer PP6DHTBT as an electron donor and PC(71)BM as an acceptor in the weight ratio of 1:4, and a power conversion efficiency value of 1.20%, an open-circuit voltage (V(oc)) value of 0.75 V, a short-circuit current (J(sc)) value of 4.60 mA/cm(2), and a fill factor (FF) value of 35.0% were achieved. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4823-4834, 2010
Synthesis and applications of main-chain Ru(II) metallo-polymers containing bis-terpyridyl ligands with various benzodiazole cores for solar cells
(2011)
Padhy, Harihara
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Sahu, Duryodhan
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Chiang, I-Hung
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Patra, Dhananjaya
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Kekuda, Dhananjay
A series of p-conjugated bis-terpyridyl ligands (M1-M3) bearing various benzodiazole cores and their corresponding main-chain Ru(II) metallo-polymers were designed and synthesized. The formation of metallo-polymers were confirmed by NMR, relative viscosity, and UV-visible titration measurements. The effects of electron donor and acceptor interactions on their thermal, optical, electrochemical, and photovoltaic properties were investigated. Due to the strong intramolecular charge transfer (ICT) interaction and metal to ligand charge transfer (MLCT) in Ru(II)-containing polymers, the absorption spectra covered a broad range of 260-750 nm with the optical band gaps of 1.77-1.63 eV. In addition, due to the broad sensitization areas of the metallo-polymers, their bulk heterojunction (BHJ) solar cell devices containing [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) as an electron acceptor exhibited a high short-circuit current (J(sc)). An optimum PVC device based on the blended polymer P1 : PCBM = 1 : 1 (w/w) achieved the maximum power conversion efficiency (PCE) value up to 0.45%, with V(oc) = 0.61 V, J(sc) = 2.18 mA cm(-2), and FF = 34.1% (under AM 1.5 G 100 mW cm(-2)), which demonstrated a novel family of conjugated polyelectrolytes with the highest PCE value comparable with BHJ solar cells fabricated from ionic polythiophene and C(60).
Synthesis and applications of novel acceptor-donor-acceptor organic dyes with dithienopyrrole- and fluorene-cores for dye-sensitized solar cells
(2011-01-14)
Sahu, Duryodhan
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Padhy, Harihara
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Patra, Dhananjaya
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Yin, Jen-Fu
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Hsu, Ying-Chan
Four novel symmetrical organic dyes (S1-S4) configured with acceptor-donor-acceptor (A-D-A) structures containing electron donating fluorene (S1 and S2) and N-alkyl dithieno[3,2-b:2',3'-d]pyrrole (DTP) (S3 and S4) cores terminated with two anchoring cyanoacrylic acids (as electron acceptors) were synthesized and applied to dye-sensitized solar cells (DSSCs). The DSSC device based on S2 dye showed the best photovoltaic performance among S1-S4 dyes: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 76%, a short circuit current (J(SC)) of 12.27 mA/cm(2), an open circuit voltage (V(OC)) of 0.61 V. a fill factor (FF) of 0.63, and an overall power conversion efficiency (eta) of 4.73%. Besides, the utilization of chenodoxycholic acid (CDCA) as a co-adsorbent in the DSSC device based on S3 dye showed a significant improvement in its eta value (from 3.70% to 4.31%), which is attributed to the suppression of dye aggregation on TiO(2) surface and thus to increase the J(SC) value eventually. (C) 2010 Elsevier Ltd. All rights reserved.
Synthesis and applications of novel low bandgap star-burst molecules containing a triphenylamine core and dialkylated diketopyrrolopyrrole arms for organic photovoltaics
(2012)
Sahu, Duryodhan
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Tsai, Chia-Hua
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Wei, Hung-Yu
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Ho, Kuo-Chuan
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Chang, Feng-Chih
In this study, we used facile synthetic routes to construct two well-defined starburst donor/acceptor conjugated small molecules with broad absorption features; in TPAKP-2 and TPAKP-3, triphenylamine (TPA) moieties served as electron donor core units and dialkylated diketopyrrolopyrrole (DKP) moieties with symmetrical thiophene units served as electron acceptors, in 1 : 2 and 1 : 3 ratios, respectively. Our investigation of the photophysical properties indicated that the absorption bands of TPAKP-2, and TPAKP-3 extended up to 793 nm, with low optical band gaps of 1.56 and 1.65 eV respectively. Under illumination with AM 1.5 white light (100 mW cm(-2)), we investigated the performance of bulk heterojunction (BHJ) photovoltaic devices incorporating an active layer of an electron-donor small molecule (TPAKP-2 or TPAKP-3) blended with an electron acceptor: [6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) at various weight ratios. The photovoltaic device containing the donor TPAKP-3 and the acceptor PC(71)BMat a 1 : 3 weight ratio exhibited the best power conversion efficiency (1.81%), with an open circuit voltage of 0.66 V, a short circuit current density of 7.93 mA cm(-2), and a fill factor of 34.7%.
Synthesis and Characterization of Novel Low-Bandgap Triphenylamine-Based Conjugated Polymers with Main-Chain Donors and Pendent Acceptors for Organic Photovoltaics
(2010-12-15)
Sahu, Duryodhan
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Padhy, Harihara
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Patra, Dhananjaya
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Huang, Jen Hsien
;
Chu, Chih Wei
A series of novel low bandgap triphenylamine based conjugated polymers (PCAZCN PPTZCN and PDTPCN) consisting of different electron rich donor main chains (N alkyl 2 7 carbazole phenothiazine and cyclopentadithinopyrol respectively) as well as cyano and dicyano vinyl electron acceptor pendants were synthesized and developed for poly mer solar cell applications The polymers covered broad absorption spectra of 400-800 nm with narrow optical band gaps ranging 1 66-1 72 eV The highest occupied molecular or bital and lowest unoccupied molecular orbital levels of the polymers measured by cyclic voltammetry were found in the range of -5 12 to -532 V and -345 to -355 eV respectively Under 100 mW/cm(2) of AM 1 5 white light illumination bulk heterojunction photovoltaic devices composing of an active layer of electron donor polymers (PCAZCN PPTZCN and PDTPCN) blended with electron acceptor [6 6] phenyl C(61) butync acid methyl ester or [6 6] phenyl C(71) butyric acid methyl ester (PC(71)BM) in different weight ratios were investigated The photovoltaic device containing donor PCAZCN and acceptor PC(71)BM in 1 2 weight ratio showed the highest power conversion efficiency of 1 28% with V(oc) = 0 81 V J(sc) = 493 mA/cm(2) and fill factor = 32 1% (c) 2010 Wiley Periodicals Inc J Polym Sci Part A Polym Chem 48 5812-5823 2010