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Solution processability is one of the advantages of organic solar cells (OSCs). However, most high-efficiency OSCs are prepared using hazardous chlorinated solvents for the deposition of photoactive layers. The replacement of non-halogenated solvents with eco-friendly green solvents for photoactive materials is urgently required. Herein, we have developed a novel asymmetric T2-OEHRH, which is modified from the symmetric T2-ORH. The introduction of asymmetric alkyl side chains onto rhodanine end groups can effectively suppress excessive self-aggregation/crystallization and substantially improve solubility without sacrificing optoelectrical properties. Therefore, ternary-blend OSCs based on PTB7-Th:EH-IDTBR:T2-OEHRH processed using a non-halogenated solvent system exhibit a uniform and favorable morphology and give a high power conversion efficiency (PCE) of 12.10%. More importantly, we demonstrate an impressive PCE of 9.32% for large-area NFA-OSCs (substrate size = 100 cm2 and aperture size = 55.5 cm2) prepared via D-bar coating in air. To our knowledge, this PCE is the highest reported to date for NFA-based large-area OSC modules processed from a non-halogenated solvent. This asymmetric alkyl-chain engineering strategy can be exploited to develop high-performance large-area NFA-OSCs with eco-friendly solvent processing.

Charge transport in molecular solids, such as semiconducting polymers, is strongly affected by packing and structural order over several length scales. Conventional approaches to modeling these phenomena range from analytical models to numerical models using quantum mechanical calculations. While analytical approaches cannot account for detailed structural effects, numerical models are expensive for exhaustive (and statistically significant) analysis. Here, we report a computationally scalable methodology using graph theory to explore the influence of molecular ordering on charge mobility. This model accurately reproduces the analytical results for transport in nematic and isotropic systems, as well as experimental results of the dependence of the charge carrier mobility on orientation correlation length for polymers. We further model how defect distribution (correlated and uncorrelated) in semiconducting polymers can modify the mobility, predicting a critical defect density above which the mobility plummets. This work enables rapid (and computationally extensible) evaluation of charge mobility semiconducting polymer devices.

A simple-structured nonfullerene acceptor (NFA), T2-ORH, consisting of a bithiophene core and octyl-substituted rhodanine ends is utilized as the third component in ternary-blend solar cells with PTB7-Th and EH-IDTBr as host materials. T2-ORH is a wide band gap NFA and specially contributes to light absorption, which provides complimentary absorption with a low band gap acceptor, EH-IDTBR. In the ternary device, a PCE of 11.55%, a short circuit current (JSC) of 17.51 mA cm−2, a fill factor (FF) of 63% and an open circuit voltage (VOC) of 1.05 V were achieved with a 1 : 1 : 1 blend ratio. In this ternary system, it is estimated that the two NFAs work as one alloy-like acceptor and energy transfer model from T2-ORH to EH-IDTBR for efficient ternary-blend organic solar cells (OSCs). On conducting thermal, light, and air-process stability tests, the ternary-blend systems show superior stability performance owing to the formation of a stable and robust morphology. Finally, we fabricated a large-scale device (5 cm × 5 cm substrate, 13.5 cm2 aperture size, and a geometric FF of 54%) with the same ternary system. The sub-module ternary-blend OSCs displayed the highest PCE of 10.08% with JSC = 2.83 mA cm−2, VOC = 6.36 V and FF = 56%. As a result, ternary-blend OSCs show tremendous promise for use in actual applications.

We developed p-n junction organic photodetectors (OPDs) composed of a polymer donor and a nonfullerene acceptor (NFA) to increase both the responsivity (R) and detectivity (D*) while maintaining a narrow wavelength selectivity. The selection of the polymer donor and NFA with similar green (G) absorption is important for achieving G-wavelength selectivity in these OPDs, which differentiates them from current fullerene-based OPDs and NFA-based panchromatic absorption OPDs. In addition, mixing the polymer donor and asymmetric NFA was efficient toward increasing the miscibility and decreasing the interfacial energy difference of the blended films, resulting in the formation of a uniform and well-mixed nanomorphology in the photoconductive layer. Two-dimensional (2D) grazing incidence X-ray diffraction and Fourier-transform infrared spectroscopy revealed that the lamellar ordering of the polymer donor was enhanced in the blend film prepared with an asymmetric NFA, whereas the aggregation of a symmetric NFA in the blend films did not increase the lamellar ordering of the polymer donor. Consequently, we achieved an R value of 0.31 A/W and D* value of 2.0 × 1013 Jones with a full width at half-maximum value of 230 nm at -2 V and fast response time of 27 μs without any external bias in the asymmetric NFA-based OPDs. The enhancement in the lamellar ordering and miscibility of the blended films are crucial toward increasing the static and dynamic properties of OPDs.

Herein, two diketopyrrolopyrrole (DPP)-based, small-molecule isomers, o- and p-DPP-PhCN, were introduced as acceptors in ternary organic solar cells (OSCs). The isomers have the same molecular backbone but differ in the positions of the cyanide (CN) substituents (ortho and para), which greatly affects their packing behavior. Ternary solar cells composed of poly(3-hexylthiophene) (P3HT):DPP-PhCN:phenyl-C61-butyric acid methyl ester (PCBM) were fabricated, and the effects of the different packing behaviors of the third component on the device performance and the working mechanism of the ternary cells were investigated. The addition of o-DPP-PhCN with a relatively high-lying lowest unoccupied molecular orbital energy level resulted in an increase in the open-circuit voltage (VOC) in the ternary devices, demonstrating the alloy-like structure of the two acceptors (o-DPP-PhCN and PCBM) in the ternary system. However, the p-DPP-PhCN-based ternary cells exhibited VOC values similar to that of a P3HT:PCBM binary cell, irrespective of the addition of p-DPP-PhCN, indicating a cascade energy-level structure in the ternary system and an effective charge transfer from the P3HT to the PCBM. Importantly, by increasing the addition of p-DPP-PhCN, the short-circuit current density increased substantially, resulting in pronounced shoulder peaks in the external quantum efficiency responses in the long-wavelength region, corresponding to the contribution of the photocurrent generated by the light absorption of p-DPP-PhCN. Despite sharing the same molecular backbone, the two DPP-PhCNs exhibited substantially different packing behaviors according to the position of their CN substituents, which also greatly affected the working mechanism of the ternary devices fabricated using the DPP-PhCNs as the third component.

Most non-fullerene acceptors (NFAs) are designed in a complex planar molecular conformation containing fused aromatic rings in high-efficiency organic solar cells (OSCs). To obtain the final molecules, however, numerous synthetic steps are necessary. In this work, a novel simple-structured NFA containing alkoxy-substituted benzothiadiazole and a rhodanine end group (BTDT2R) is designed and synthesized. We also investigate the photovoltaic properties of BTDT2R-based OSCs employing representative polymer donors (wide band gap and high-crystalline P3HT, medium band gap and semicrystalline PPDT2FBT, and narrow band gap and low-crystalline PTB7-Th) to compare the performance capabilities of fullerene acceptor-based OSCs, which are well matched with various polymer donors. OSCs based on P3HT:BTDT2R, PPDT2FBT:BTDT2R, and PTB7-Th:BTDT2R achieved efficiency as high as 5.09, 6.90, and 8.19%, respectively. Importantly, photoactive films incorporating different forms of optical and molecular ordering characteristics exhibit favorable morphologies by means of solvent vapor annealing. This work suggests that the new n-type organic semiconductor developed here is highly promising as a universal NFA that can be paired with various polymer donors with different optical and crystalline properties.

An acceptor-donor-acceptor (A–D–A)-type small molecule, BDT-IN, having a benzo[1,2-b:4,5-b']dithiophene (BDT) unit as its electron-donating core (D) and an 1,3-indanedione (IN) unit as its electron-withdrawing end group (A), was synthesized by Knoevenagel condensation. The BDT-IN film showed broader UV absorption with a greater red shift (λmax = 622 nm) than that of the BDT-IN solution (λmax = 570 nm). The organic photovoltaic cells were fabricated with an ITO/PEDOT:PSS/poly(3-hexylthiophene): BDT-IN/LiF/Al configuration, and showed a power conversion efficiency of 0.23%.

The donor–acceptor–donor (D–A–D) type small molecule, TPD2T, was synthesized by the Stille coupling reaction and consisted of the electron-withdrawing thiene[3,4-c]pyrrole-4,6-dione (TPD) unit as a...

A series of D–A–D type small molecules containing thiophene and benzo[1,2,5]thiadiazole (BT) as electron-donating and electron-accepting units, respectively, were synthesized using palladium-catalyzed Suzuki coupling reactions. The electron-accepting units of BT were modified with pyridyl nitrogen, a single fluorine atom, or two fluorine atoms to enhance their electron-withdrawing abilities, which resulted in DH5TPys, F-DH5TBs, or 2F-DH5TBs, respectively. The solubilizing hexyl groups were introduced at two different β-positions (3- and 4-positions) on both ends of the thiophene rings. The optical, electrochemical, and photovoltaic properties of the small molecules varied, depending on the introduction of the electron-withdrawing substituents as well as the alkyl variation. The highest occupied molecular orbital (HOMO) energy levels of the small molecules were decreased by the increasing number of fluorine substituents; 4-substitution resulted in deeper HOMO energy levels than 3-substitution. 2F-DH5TB-4 had the lowest HOMO energy level of −5.49 eV. In the organic photovoltaic cells with the configuration ITO/PEDOT:PSS/small molecule:PC71BM/LiF/Al, 2F-DH5TB-4 showed the highest power conversion efficiency (PCE) of 1.11 % owing to the lowest HOMO levels and thus increased the open-circuit voltage. However, two DH5TPys showed low PCEs of 0.20 % despite the deep HOMO energy levels and good UV absorption because of the protonation of pyridyl nitrogen with acidic PEDOT:PSS. In the inverted structure of ITO/ZnO/small molecule:PC71BM/MoO3/Ag, both DH5TPys showed improved PCE values of up to 1.16 %. The device performance of 2F-DH5TB-4 also improved in the inverted structure, showing the PCE of 1.27 %.

In this work, we utilized two fluorene-based polymers (F8TBTT and F8TTZT) as donor materials in organic photovoltaic cells (OPVs) and compared their performance to explain the effect of substituting fused thiazolothiazole for the bithiazole moiety. The OPV device based on F8TTZT showed a power conversion efficiency of 0.24%, which is three times higher than that of F8TBTT (0.07%) under the same conditions. The better performance can be explained by the increased planarity and enhanced intermolecular charge transport.

The introduction of oligothiophenes (b-5T and b-5TB) improved the performance of F85TB:PCBM bulk heterojunction OPV cells due to improved UV-vis absorption and the well-matched cascade energy levels between components.

We synthesized a linear π-conjugated small molecule (β-DH5T) based on thiophene, using the palladium-catalyzed Suzuki coupling. The oligothiophene was designed to contain β-substituted solubilizing alkyl groups to facilitate solution processing. The organic photovoltaic cell based on β-DH5T:PC71BM gave a power conversion efficiency of 0.46% with a short-circuit current of 4.69 mA/cm2, an open-circuit voltage of 0.60 V, and a fill factor of 0.35, giving under AM 1.5G illumination (100 mW/cm2). The optical and electrochemical properties and molecular alignment of oligothiophene were investigated using UV-visible absorption spectroscopy, cyclic voltammetry, and thin-film X-ray diffraction studies.

Polymer-capped silicon nanoparticles (Si NPs) were prepared using poly(vinylpyrrolidone) (PVP) as a protection layer to minimize the surface oxidation of the surface. The wet synthetic procedure were performed at room temperature via a one-pot synthesis. The PVP capped Si-NPs were characterized by thermo gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), high resolution transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FE-SEM). HR-TEM micrograms confirm the presence of crystalline Si-NPs. The pattern by Selected Area Electron Diffraction (SAED) reveals (111), (220) lattice planes which are consistent with the cubic-structured crystalline silicon. The mean size of Si-NPs is estimated to be ca. 10 nm, which is larger than those from conventional wet synthetic methods for silicon quantum dots.

Two benzo[1,2-b:4,5-b’]dithiophene and thiophene-based materials, a small molecule (SM-BDT) and a polymer (P-BDT), were synthesized and their photovoltaic properties were investigated by fabricating their binary and ternary cells. The introduction of the ternary blend system effectively enhanced device performance. The power conversion efficiency (PCE) of the ternary SM-BDT:P-BDT:[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) film (0.19%) was nearly double that of the pristine binary films of SM-BDT:PCBM and P-BDT:PCBM. The optical and electrochemical properties were investigated to explain the improved photovoltaic properties of the ternary blended cells.

Two π-conjugated small molecules based on diketopyrrolopyrrole (DPP), DPP4T and DPP2F2T, were synthesized using the Suzuki coupling reaction. DPP4T and DPP2F2T contained furan and thiophene, respectively, next to a DPP core. Organic photovoltaic cells (OPVs) were fabricated using two DPP-based oligothiophenes as donors. DPP4T showed higher power conversion efficiency (PCE) (1.44%) than DPP2F2T (0.85%). The short-circuit current (JSC) of DPP4T (4.38 mA cm−2) was nearly twice that of DPP2F2T (2.49 mA cm−2). The improved photovoltaic properties of DPP4T could be explained by the optical properties and the film morphology.

T.L. and Y.E. contributed equally to this work. This work was financially supported by the Korea Institute of Energy Technology Evaluation & Planning (KETEP) and the Ministry of Trade, Industry & Energy (No. 20173010012960) and by the National Research Foundation of Korea (NRF) Grant funded by the Ministry of Science & ICT (NRF-2015R1A1A3A04001498 & NRF-2019R1A2C1003679) of the Republic of Korea.

A series of fluorene-thiophene-based pi-conjugated copolymers, PFT2, PFT4, and PFT2BP, have been synthesized using the Suzuki coupling reaction. Compared to PFT2 and PFT2BP, PFT4 film showed clearly red-shifted UV-visible absorption and photoluminescence (PL) spectra with maxima at 474 and 597 nm, respectively. The optical and electrochemical properties of copolymers could be tuned by changing conjugation lengths of comonomer units from bithiophene (PFT2) to quaterthiophene (PFT4). Moreover, PFT4 containing quaterthiophene showed relatively lower optical band gap of 2.16 eV. The organic photovoltaic cells (OPVs) were fabricated using the copolymers as donor with a sandwich configuration of ITO/PEDOT:PSS/copolymer:PC71BM/LiF/Al. PFT4 showed the best device performance with the optimized power conversion efficiency (PCE) of 2.26% (J(SC) = 7.67 mA/cm2, V(OC) = 0.81 V, FF = 0.36). The higher OPV performance of PFT4 can be explained by its relatively low energy band gap and improved UV absorption property.

This paper reports the synthesis and characterization of a new vinazene-based small molecule, 4,7-bis(2-(1-(2-ethylhexyl)-4,5-dicyanoimidazol-2-yl) vinyl)diketopyrrolopyrrole (EV-DPP). The known vinazene-based small molecule, 4,7-bis(2-(1-(2-ethylhexyl)-4,5-dicyanoimidazol-2-yl)vinyl)benzo[c][1,2,5]thiadizole (EV-BT), was also prepared for comparison. The benzothiadiazole unit in EV-BT was replaced with a DPP unit in EV-DPP because DPP units are strong absorbing chromospheres. The UV absorption maxima of EV-DPP film (λ max = 386, 573 nm) were greatly red shifted compared to the maxima of EV-BT film (λ max = 337, 444 nm). Our preliminary device work showed the possibility of the use of EV-DPP as an electron acceptor in OPVs. The P3HT: EV-DPP film showed a better power conversion efficiency of 0.02% compared to P3HT: EV-BT due to the preferable UV absorption characteristics of EV-DPP.

Poly(3,4-ethylenedioxythiophene) (PEDOT)-indium tin oxide (ITO) nanocomposites were synthesized via a solution route. The electrochromic behavior of the devices was investigated in terms of particle sizes, dispersibility and electrical conductivity of the nanocomposites. The electrical conductivity of PEDOT-ITO composite thin films were in the range of 0.1∼15 S/cm with transparency changes from 25% to 85%. The electrochromic properties of the nanocomposite as an active material for the devices (ECDs) are discussed in terms of conductivity and transparency. The electrochromic behavior was confirmed with colored state and blanched state at +3.1 V∼−2.9 V which transparency difference about 50∼60% at 600 nm. The switching speeds of the ECD are closely correlated with the changes in the electrical conductivity and the morphology of the nanocomposite.

New conjugated polymers based on benzo[1,2-b:4,5-b']dithiophene, poly(benzo[1,2-b:4,5-b'] dithiophene-alt-bithiophene) (PBT-2T) and poly(benzo[1,2-b:4,5-b']dithiophene-alt-terthiophene) (PBT-3T), have been synthesized via the Stille coupling reaction and their optical and electrochemical properties were characterized by UV-vis, photoluminescence (PL) and cyclic voltammetry (CV) measurements. Compared to PBT-2T, PBT-3T film showed clearly red-shifted UV-visible absorption and PL spectra with maxima at 511 and 653 nm, respectively. Especially, PBT-3T containing terthiophene showed very small optical band gap of 1.65 eV. The PBT-2T and PBT-3T showed the power conversion efficiencies of 0.25% and 0.34%, respectively, under AM 1.5 (100 m/cm2).

In this paper, we have synthesized a series of fluorene-thiophene-based copolymers by Suzuki coupling polymerization for the use of donor materials in organic photovoltaic cells (OPVs). New conjugated polymers have an electron-deficient moiety such as benzothiadiazole (BT), oxadiazole (OX) and triazole (TZ) or an electron-rich triphenylamine (TPA) moiety or both in the main chains as third or fourth comonomers. The photovoltaic properties of the polymers were varied by introduced electron- or hole-transporting units. The order in the efficiency of the photovoltaic cells was P1 (BT)

The ink-jet printing method is an important process in display industry due to the low-cost production of large-scale electronic devices. In this work, we prepared the nanoparticle indium tin oxide (ITO) solutions for ink-jet printing and characterized the electrical, structural and morphological properties of the film. The improvement of conductivity after reduction process was correlated with the sharpening of the diffraction peak as proved by X-ray diffraction measurement. The ITO inks was coated on a glass by spin-coating process and patterned by the ink-jet printing technique using a 50 μm diameter ink-jet nozzle. The sheet resistance and optical transmission of ITO thin film was ca. 50∼300Ω/sq and ca. 75∼95%, respectively. The electrical resistance of patterned ITO lines showed about 5∼30 ∗ 103Ω. The detailed relationship between microstructure and properties are discussed.

Graphene sheets were produced by chemical reduction of graphite oxides in the solution of ionic conductive polymer, Nafion. The obtained graphene, coated with Nafion, can be re-dispersed in water, and readily forms stable dispersed state. The polymer-coated graphene had been characterized by FT-IR spectroscopy, UV–vis and X-ray photoelectron spectroscopy (XPS). The PEDOT film with Nafion-coated graphene increased significantly from 0.25 S/cm for pure PEDOT film and reached 12 S/cm. Further, the films of PEDOT doped Nafion-coated graphene had also higher conductivities compared to films doped PSS-coated graphene.

A series of linear π-conjugated oligothiophenes, α,α'-dihexylquinquethiophene (DH5T), 2,5-bis(5'-hexyl-2,2'-bithiophene-5-yl)thieno[3,2-b]thiophene (DH5TT), and α,α'-dihexylheptathiophene (DH7T), has been synthesized using the Suzuki coupling reaction. The optical and electrochemical properties of oligothiophenes were easily tuned by controlling the thiophene number. The UV-vis absorption and photoluminescence (PL) spectra are gradually red-shifted on going from DH5T and DH5TT to DH7T due to the increase in α-conjugation length. The energy band gap decreased as the oligothiophene length increased. The optical band gaps of DH5T, DH5TT, and DH7T occur at 2.39, 2.25, and 2.01 eV, respectively. Bulk heterojunction organic photovoltaic cells (OPVs) fabricated from oligomers showed the power conversion efficiency of 0.45-0.8% under AM 1.5 (100 mW/cm2). Among them, DH5T showed the best OPV performance of an open circuit voltage (VOC) of 0.51 V, short-circuit current (JSC) of 4.25 mA/cm2, and fill factor (FF) of 0.37, resulting in the power conversion efficiency of 0.80%. Moreover, the relationship between conjugation length and photovoltaic properties was systematically investigated in terms of the energy band gap and open circuit voltage (VOC).

Random copolymers, PFDEP13 and PFDEP26, were synthesized through Ni(0)-mediated polymerization with 2,7-dibromo-9,9-di-n-hexylfluorene and 1-[2-(2,5-dibromo-4-{2-[4-(2-ethylhexyloxy)phenyl]vinyl}phenyl)vinyl]-4(2-ethylhexyloxy)-benzene (DEP). The resulting polymers are soluble in aprotic polar organic solvents and show good thermal stability up to ca. 400°C. The photoluminescence (PL) emission peaks of the two copolymers are red-shifted with respect to that of common polyfluorene (PF) homopolymer. Both the EL spectra of PFDEP13 and PFDEP26 show maximum emission peaks at 470 nm. In particular, PFDEP26 exhibits a broad emission spectrum in the whole visible region, which suggests the possibility of PFDEP26 as a white-light-emitting polymer.

A novel approach to enhancing the performance of solution-processed n-type organic field-effect transistors by using trace amounts of molecular "aligners" to manipulate the assembly of "matrix" molecules in thin films is demonstrated. The device performance is one order of magnitude higher in 1wt% blended thin films than that in neat films, which correlates to an induced change of preferred orientation of the in-plane π-stacking molecules upon blending.

We have synthesized a series of carbazole-benzothiadiazole-triazole based copolymers, poly[(N-9′-heptadecanyl-2,7-carbazole)-co-(5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole))-co-((4-(4-butylphenyl)-3,5-diphenyl-4H-1,2,4]triazole))] (PCz3TBTz) by Suzuki coupling polymerization. The optical and electrochemical properties of the copolymers could be tuned by changing the comonomer unit of triazole from 0% to 80%. Organic photovoltaic (OPV) cells were fabricated by blending the synthesized polymers as a donor and PCBM as an acceptor. The material solubility and film morphology were improved by introducing the triazole unit in the main chain. Improved OPV device performance of 1.74% was achieved in the presence of an optimal amount of triazole moieties.

A new low-band gap polymer containing thiophene and cyclopentadiene, poly(5,2,2'-dioctyldithio-phenylcyclopentadiene) (PDTCP), has been synthesized via the FeCl3 oxidative polymerization. PDTCP showed a broad absorption band and a low energy band gap of 1.82 eV. The photoluminescence (PL) of PDTCP is completely quenched upon addition of PCBM indicative of efficient charge transfer. Bulk heterojunction organic photovoltaic cells (OPVs) fabricated from PDTCP as an electron donor showed an open-circuit voltage (V(OC)) of 0.50 V, a short-circuit current (J(SC)) of 1.24 mA/cm2, and the power conversion efficiency of up to 0.20% under AM 1.5 (100 mW/cm2).

A white light-emitting diode was fabricated by preparing multilayer emitting films with an inserted buffer layer. The device structures are ITO/PEDOT:PSS/Emissive layer/LiF/Al. The emissive layer comprises a yellow-emitting layer of Poly[9,9-dioctylfluorenyl-2,7-diyl]-co-1,4-benzo-(2,1,3)-thiadiazole (F8BT), a blue-emitting layer of Poly[9,9-di-(2'-ethylhexyl)fluorenyl-2,7-diyl] (BEHF) and PEDOT:PSS as a buffer layer between the emission layers. The solution processed multi-layer polymer light-emitting diodes (PLED) were prepared by introduction of a water-soluble buffer layer between organic solvent soluble layers. We present white organic light-emitting diodes (WOLEDs) that has bilayer emission zones. This device exhibits a brightness of 280 cd/m2 and emission efficiency of 1.18 cd/A at 12.6 V. The device with a doped PEDOT:PSS layer and a thicker blue-emission layer exhibits CIE color coordinates of (0.30, 0.34), which is close to the white coordinates of (0.33, 0.33) used by the standard CIE color coordinates.

An electron-transporting triazole (Tz) unit was introduced into the fluorene-thiophene-based copolymer backbone via a Suzuki coupling reaction. The resulting copolymer, poly[9,9'-dioctyl-fluorene-co-5, 5-(4', 7'-di-2-thienyl-2', 1',3'-benzothiadiazole)-co-(4-(4-butyl-phenyl)-3, 5-diphenyl-4H-1,2,4]triazole)] (PF3TBTz), was soluble in common organic solvents and can be easily used as the active layer in organic photovoltaic cells (OPVs). By the introduction of the triazole unit, the OPV performance was nearly doubled from 0.62% (PF3TB) to 1.25% (PF3TBTz) under the same conditions. The higher performance can be explained by the improved surface morphology, resulting in better charge photogeneration and higher short circuit current (J(sc)) value in PF3TBTz in comparison with PF3TB. The possibility of the use of triazole units in OPV applications are described herein.

The regioregular hexyl-substituted poly(3,4-ethylenedioxy-2-thiophenylthiophene) (PEDOTt), structurally alternating copolymer of EDOT and thiophene, was synthesized via the Grignard Metathesis (GRIM) using catalytic amounts of Ni(dppp)Cl2. The products were characterized by 1H NMR spectroscopy, UV-vis spectroscopy and XRD. The alkyl-substituted conjugated polymer showed an enhancement of solubility in common organic solvents. Based on XRD data, the regioregular hexyl-substituted poly(3,4-ethylenedioxy-2-thiophenylthiophene) (PEDOTt) shows better crystallinity than the regiorandom hexyl-substituted PEDOTt owing to self-ordering. In addition, regioregular hexyl-PEDOTt has a conductivity of 0.788 S/cm by iodine doping.