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Design and synthesis of low bandgap (LBG) polymer donors is inevitably challenging and their processability from a non-halogenated solvent system remains a hurdle to overcome in the area of high-performance polymer solar cells (PSCs). Due to a high aggregation tendency of LBG polymers, especially diketopyrrolopyrrole (DPP)-based polymers coupled with bithiophenes in the polymer backbones, their widespread adoption in non-halogenated solvent-processed PSCs has been limited. Herein, a novel LBG DPP-based polymer, called PDPP4T-1F with asymmetric arrangement of fluorine atom, has been successfully synthesized and showed an outstanding power conversion efficiency (PCE) of 10.10% in a single-junction fullerene-based PSCs. Furthermore, an impressive PCE of 13.21% has been achieved in a tandem device from a fully non-halogenated solvent system, which integrates a wide bandgap PDTBTBz-2F polymer in the bottom cell and LBG PDPP4T-1F polymer in the top cell. The achieved efficiency is the highest value reported in the literature to date in fullerene-based tandem PSCs. We found that a uniformly distributed interpenetrating fibril network with nano-scale phase separation and anisotropy of the polymer backbone orientation for efficient charge transfer/transport and suppressed charge recombination in PDPP4T-1F-based PSCs led to outstanding PCEs in single and tandem-junction PSCs.

A new wide bandgap (WBG) conjugated polymer diO-PBDB-T containing alkoxy substituted thiophene spacer was designed and synthesized for application as a donor in nonfullerene acceptor (NFA) based po...

In this study, the effect of radiation deterioration on cable fire for a type of class 1E cable for a nuclear power plant was investigated. Combustion and smoke characteristics were compared via a cone calorimeter test (ISO 5660-1), and the toxicity index of the toxic gas emitted during combustion was analyzed by following the NES 713 standard. The peak heat release rate of the irradiated cable was measured to be approximately 38 kW/m2 higher than that of the non-irradiated cable. Additionally, the heat release rate of the irradiated cable temporarily increased during a certain period. This can be ascribed to the continuous pyrolysis and heat penetration as a result of the unstable formation of the char layer. The total heat release of the irradiated cable was measured to be approximately 2.2 times higher than that of the non-irradiated cable. A corresponding increase of ~2.8% in the total mass loss was observed. In the case of smoke characteristics, the irradiated cable was measured to be 2.3 times higher in the smoke parameter and 3.8 times higher in the smoke factor compared to the non-irradiated cable. For the toxicity index, only CO was detected above the critical factor in the non-irradiated cable, whereas both CO and HBr were detected above their critical factors in the irradiated cable.

A–D–A′–D–A-type nonfused-ring acceptors (NFRAs) have recently received extensive attention because of their suitable tuning of absorption spectra, frontier energy levels, and promising sunlight har...

Two 1,3-bis(thiophen-2-yl)−5,7-bis(2-ehtylhexyl)benzo-[1,2-c:4,5-c]-dithiophene-4,8-dione (BDD) based small molecules, SM1 and SM2 are designed and synthesized by incorporating benzodithiophene (BD...

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.

Organic-inorganic hybrid perovskites have recently attracted substantial attention as a top candidate for use as light-absorbing materials in high-efficiency, low-cost and solution-processable photovoltaic devices owing to their excellent optoelectronic properties. Here, we fabricated inverted planar perovskite solar cells by incorporating small amounts of ammonium halide NH4X (X = F, Cl, Br, I) additives into a CH3NH3PbI3 (MAPbI3) perovskite solution. A compact and uniform perovskite absorber layer with large perovskite crystalline grains is realized by simply incorporating small amounts of additives and by using an anti-solvent engineering technique to control the nucleation and crystal growth of perovskite. The enlarged perovskite grain size with a reduced density of the grain boundaries and improved crystallinity results in fewer charge carrier recombinations and a reduced defect density, leading to enhanced device efficiency (NH4F: 14.88 ± 0.33%, NH4Cl: 16.63 ± 0.21%, NH4Br: 16.64 ± 0.35%, and NH4I: 17.28 ± 0.15%) compared to that of a reference MAPbI3 device (Ref.: 12.95 ± 0.48%) and greater device stability. This simple technique involving the introduction of small amounts of ammonium halide additives to regulate the nucleation and crystal growth of perovskite films translates into highly reproducible enhanced device performance.

A tissue-like skin-device interface was prepared by using ultrathin functionalized hydrogels for wearable bioelectronics., Hydrogels consist of a cross-linked porous polymer network and water molecules occupying the interspace between the polymer chains. Therefore, hydrogels are soft and moisturized, with mechanical structures and physical properties similar to those of human tissue. Such hydrogels have a potential to turn the microscale gap between wearable devices and human skin into a tissue-like space. Here, we present material and device strategies to form a tissue-like, quasi-solid interface between wearable bioelectronics and human skin. The key material is an ultrathin type of functionalized hydrogel that shows unusual features of high mass-permeability and low impedance. The functionalized hydrogel acted as a liquid electrolyte on the skin and formed an extremely conformal and low-impedance interface for wearable electrochemical biosensors and electrical stimulators. Furthermore, its porous structure and ultrathin thickness facilitated the efficient transport of target molecules through the interface. Therefore, this functionalized hydrogel can maximize the performance of various wearable bioelectronics.

Perylene diimide (PDI)-based molecular acceptors, denoted PDI-TVT-PDI, PDI-FTVT-PDI, and PDI-CNTVT-PDI, which have different core units, were synthesized and evaluated as n-type materials in fullerene-free organic solar cells (OSCs). The effects of the addition of fluorine and cyano groups to (E)-1,2-di-(thiophen-2-yl)ethene (TVT) in the synthesized acceptors were investigated based on the optical and electrochemical properties and computational calculations, as well as observation of the morphologies of the blend films. Among the synthesized acceptors, PDI-CNTVT-PDI showed a high absorption coefficient, balanced hole/electron mobility ratio, predominant face-on structure, and smooth morphology in the blends with poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th). The fabricated OSCs using PTB7-Th/PDI-CNTVT-PDI exhibited a higher power conversion efficiency (PCE, 4.32%) than those fabricated with PTB7-Th/PDI-TVT-PDI and PTB7-Th/PDI-FTVT-PDI. The purpose of our study is to provide a facile strategy to understand the impact of the core units to enable the design of PDI-based molecular acceptors.

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.

Photostability of the polymer solar cells (PSCs) remains a challenge to attain, as number of factors including the electron transport layers contribute to the degradation of PSCs when they are tested under 1 sun illumination, along with heat and humidity. Especially electron transport layers (ETLs) have considerable contribution to the overall degradations in these solar cells. Most studied ETL into the fabrication of inverted PSCs is zinc oxide (ZnO) yet the photostability of these PSCs is limited. This degradation most probably occurred due to the direct contact of zinc metal with the photoactive layer. This interface between ZnO and photoactive layer results in the initiation of degradations in PSCs. Keeping in view of this issue, we have modified the ZnO ETL by mixing ZnO nano particles with ethoxylated polyethyleneimine (PEIE) and then passivating this modified ZnO (m-ZnO) with ultrathin PEIE buffer layer. The power conversion efficiency is not affected by this approach, but when PSCs were subjected to 1 sun illumination, these m-ZnO/PEIE based PSCs have shown the enhanced light soaking (LS) stability. These findings indicate that optimizing the interface between the photoactive layer and the electron transport layer can lead to enhanced LS stability.

PNTz4T-based polymers have been extensively employed in high-efficiency fullerene-based polymer solar cells (PSCs) with a power conversion efficiency (PCE) of approximately 10.0% due to the high crystallinity of these polymers. The introduction of two fluorine atoms into PNTz4T to synthesize the PNTz4T-2F polymer has boosted the PCE to 10.6%, but the introduction of four fluorine atoms to synthesize the PNTz4T-4F polymer negatively affects the efficiency (PCE = 6.5%), implying that the number of fluorine atoms is not yet optimized. We have developed a new synthetic route for a novel monofluoro-bithiophene monomer and successfully synthesized a novel PNTz4T-1F polymer. The fullerene-based PSCs based on our novel PNTz4T-1F polymer processed using a halogen-free solvent system demonstrated an outstanding PCE of 11.77% (11.67% certified), representing the highest PCE reported thus far in the literature. Due to the optimum molecular ordering/packing, improved interaction with PC71BM and interconnectivity between photoactive material domains, PNTz4T-1F-based PSCs exhibit lower charge carrier recombination and enhanced charge carrier mobility levels, leading to a substantially high photocurrent density (20.37 mA cm−2). These results create new means to tune the structural properties of polymers, ultimately leading to the realization of this class of solar cells for practical applications.

Energy level alignment between a donor and an acceptor has a critical role in determining the open-circuit voltage ( VOC) in polymer solar cells (PSCs). Also, broad absorption of the photoactive layer is required to generate a high photocurrent. Herein, non-fullerene PSCs with D/A random copolymers and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3- d:2',3'- d']- s-indaceno[1,2- b:5,6- b']dithiophene (ITIC) has been demonstrated. The D/A random copolymers are composed of a 2-ethylhexylthienyl-substituted benzo[1,2- b:4,5- b']dithiophene (BDT) donor unit (D) and a fluorinated thieno[3,4- b]thiophene (TT-F) acceptor unit (A). By controlling the D/A unit ratio in the polymer backbone, it is possible to modulate both the energy levels and absorption spectra of random copolymers. As the ratio of the donor unit in the polymer back bone increases, the highest occupied molecular orbital energy level is located deeper, leading to higher VOC. Also, the absorption spectra of random copolymers become blue-shifted with an increase of the donor unit ratio; it compensates the weak absorption region of ITIC. This complementary absorption enhances the photocurrent, leading to higher power conversion efficiency (PCE). Because of the optimization of the D/A ratio of random copolymers, a notable PCE of 10.27% can be achieved in PSCs with D5A and ITIC.

To utilize the potential of small-molecule-based organic solar cells, proper designs of the photoactive materials which result in reasonable performance in a halogen-free solvent system and thickness tolerance over a range are required. One of the best approaches to achieve these requirements is via the molecular engineering of small-molecule electron donors. Here, we have modified a previously reported dithienobenzodithiophene (DTBDT)-based small molecule (SM1) via the dimerization approach, that is, the insertion of an additional DTBDT into the main backbone of the small molecule (SM2). An SM1-based photoactive film showed severe pinhole formation throughout the film when processed with a halogen-free o-xylene solvent. On the other hand, the modified small-molecule SM2 formed an excellent pinhole-free film when processed with the o-xylene solvent. Because of the dimerization of the DTBDT in the SM2 core, highly crystalline films with compact lamellae and an enhanced donor/acceptor interdigitation were formed, and all of these factors led to a high efficiency of 8.64% with chloroform and 8.37% with the o-xylene solvent systems. To the best of our knowledge, this study represents one of the best results with the SM donor and fullerene derivative acceptor materials that have shown the device performance with halogen-free solvents.

A novel series of benzodithiophene-4,8-dione (BDD)-based copolymers, poly[(4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indacenodithiophene-2,7-diyl)-alt-(1,3-bis(2-ethylhexyl)-5,7-di(thiophene2-yl)benzodithiophene-4,8-dione)] (P1) and poly[(5,5,11,11-tetrakis(4-hexylphenyl)dithieno[2,3-d: 2',3'-d']-s-indacenodithiophene-3,9-diyl)-alt-(1,3-bis(2-ethylhexyl)-5,7-di(thiophene-2-yl)benzodithiophene-4,8-dione)] (P2), which have the same acceptor moiety but different donor segments, have been designed and synthesized for use as donor materials in solution-processable polymer solar cells (PSCs). The optical and photovoltaic properties of the copolymers were investigated. The band gaps of the copolymers were in the range 1.91-1.92 eV. Under optimized conditions, the BDD-based polymers showed power conversion efficiencies (PCEs) for the PSCs in the range 2.52-2.92% under AM 1.5 illumination (100 mW/cm2). Among the copolymers, P1, which contained an indacenodithiophene donor unit, showed a power conversion efficiency of 2.92% with a short circuit current of 7.30 mA/cm2, open circuit voltage of 0.92 V, and a fill factor of 0.43, under AM 1.5 illumination (100 mW/cm2).

The data provided in this data set is the study of organic-inorganic hybrid perovskite solar cells fabricated through incorporating the small amounts of ammonium halide NH4X (X = F, Cl, Br, I) additives into a CH3NH3PbI3 (MAPbI3) perovskite solution and is published as “High-Performance CH3NH3PbI3 Inverted Planar Perovskite Solar Cells via Ammonium Halide Additives”, available in Journal of Industrial and Engineering Chemistry [1]. A compact and uniform perovskite absorber layer with large perovskite crystalline grains, is realized by simply incorporating small amounts of additives into precursor solutions, and utilizing the anti-solvent engineering technique to control the nucleation and growth of perovskite crystal, turning out the enhanced device efficiency (NH4F: 14.88 ± 0.33%, NH4Cl: 16.63 ± 0.21%, NH4Br: 16.64 ± 0.35%, and NH4I: 17.28 ± 0.15%) compared to that of a reference MAPbI3 device (Ref.: 12.95 ± 0.48%). In addition, this simple technique of ammonium halide addition to precursor solutions increase the device reproducibility as well as long term stability. Keywords: CH3NH3PbI3 perovskite, Inverted planar structure, Ammonium halide additives, anti-solvent engineering, Perovskite grain size

Semi-transparent plastic solar cells are currently highly attractive for their potential as the most prominent components for building-integrated photovoltaics. However, the power conversion efficiency (PCE) of semi-transparent plastic solar cells still lags behind due to the lack of a suitable transparent top electrode which can be easily fabricated. Here, we demonstrate high performance semi-transparent plastic solar cells by introducing an oxide-metal-oxide (OMO) multilayer composed of MoO3 and Ag as a transparent top electrode. Because the conductivity of the OMO electrode is governed by an intermediate Ag layer sandwiched between 2 MoO3 layers, the PCE also strongly depends on the thickness of the intermediate Ag layer in the OMO electrode. By controlling the thickness of Ag layer, we obtained various PCE values from 4.5% with ~50% maximum transparency in the visible region to 9.1% with ~5% maximum transparency in the visible region. In addition, in order to get closer to practical application, 2 sizes of mini-module devices were fabricated on a larger (10.0 cm × 10.0 cm) substrate for outdoor operation and small-sized (7.0 cm × 5.0 cm) substrates for indoor operation were demonstrated using 3 materials of different color.

Material extrusion processes have been increasingly employed in the fabrication of advanced ceramics in the aerospace, automotive, and biomedical fields. Such processes—which involve printing compositions containing ceramic powders and sacrificial binder, debinding the binders, and sintering the parts to obtain pure ceramics—can be used to produce more complex structures than traditional ceramic manufacturing techniques. In this study, a rod-shaped feedstock comprised of binder-coated zirconia containing 87 wt% zirconia was supplied to a motorized piston extruder in a customized 3D printer to fabricate green ceramic structures, and the structures were then subjected to debinding and sintering. A comprehensive set of characteristics were examined: the thermal and rheological properties of the feedstock, the printability of the feedstock, the influence of the layer thickness and raster angle on the surface roughness and flexural/tensile/compressive strengths of the sintered zirconia, Vickers hardness, relative density and porosity, shrinkage behavior, and the micro/macro structure of green and sintered 3D-printed zirconia structures. The mechanical properties and relative density were found to increase as the layer thickness decreased. The maximum flexural, tensile, and compressive strengths of the sintered zirconia were 435, 36.13, and 689 MPa, respectively, and the relative density was 98.85% at a layer thickness of 200 µm. The comprehensive characteristics of 3D printed green and sintered zirconia that were obtained in this study can facilitate the successful 3D printing of ceramics. Moreover, the characterization contributes to an understanding of the effects of additive manufacturing process parameters on the physical and mechanical properties of ceramic materials and can aid in optimizing the performance and properties of 3D printed ceramic structures.

The reduction of charge carrier recombination and intrinsic defect density in organic–inorganic halide perovskite absorber materials is a prerequisite to achieving high-performance perovskite solar cells with good efficiency and stability. Here, we fabricated inverted planar perovskite solar cells by incorporation of a small amount of excess organic/inorganic halide (methylammonium iodide (CH3NH3I; MAI), formamidinium iodide (CH(NH2)2I; FAI), and cesium iodide (CsI)) in CH3NH3PbI3 perovskite film. Larger crystalline grains and enhanced crystallinity in CH3NH3PbI3 perovskite films with excess organic/inorganic halide reduce the charge carrier recombination and defect density, leading to enhanced device efficiency (MAI+: 14.49 ± 0.30%, FAI+: 16.22 ± 0.38% and CsI+: 17.52 ± 0.56%) compared to the efficiency of a control MAPbI3 device (MAI: 12.63 ± 0.64%) and device stability. Especially, the incorporation of a small amount of excess CsI in MAPbI3 perovskite film leads to a highly reproducible fill factor of ...

A series of D–A1–D–A2 type regioregular copolymers based on difluorobenzothiadiazole (DFBT) and dialkoxybenzothiadiazole (ROBT) structures was synthesized. The copolymers were prepared with different alkyl chain lengths and branching point positions. The weaker acceptor, ROBT, was incorporated as a solubilizing moiety, while the stronger acceptor, DFBT, was used to enhance intramolecular charge transfer interactions with low-lying frontier orbital levels. The design of DFBT–ROBT copolymers ensures good planarity via intrachain noncovalent F⋯S, S⋯O, and F⋯H coulombic interactions. Changing the alkyl chain branching point and length had pronounced effects on the interchain packing and charge carrier transport/recombination characteristics of the resultant polymers, which in turn influenced their photovoltaic performances. P2 (with 3-hexylundecyloxy) showed tight π–π stacking, high charge mobility, reduced bimolecular charge recombination, and an optimal nanoscale morphology compared to P1 (with 2-hexyldecyloxy). We prepared photovoltaic devices containing a blend of the copolymers with [6,6]-phenyl-C71-butyric acid methyl ester, and the resultant devices showed high power conversion efficiencies, 8.27% for P2, which is higher than that of P1 (6.87%). Furthermore, the alkyl side-chain length in P2 was varied systematically to study the correlation between the alkyl chain length in the interchain packing and photovoltaic performances. The variation in the alkyl chain branching was effective to modulate intermolecular packing to improve the photovoltaic performances. The optimum side chain length should be determined by carefully considering the solubility and interchain packing interactions.

A newly synthesized small molecule donor, BDTT-2DPPBFu, is designed for incorporation into the photo-active layer in solution-processed small molecule organic photovoltaics (SM-OPVs). The effects of a solvent additive (1-chloronaphthalene, CN) on the bulk heterojunction morphology of a BDTT-2DPPBFu donor:fullerene derivative acceptor (PC71BM) are investigated and correlated with the device performance. A TEM analysis revealed that the nanomorphology of the SM-OPVs evolved dramatically with increasing solvent additive volume. With an optimum concentration of 2.5 vol% CN, a nanomorphology with a fibrillar and interpenetrating network on the order of exciton diffusion length (∼10–15 nm) is formed, resulting in improvement of the short-circuit current density, fill factor, and power conversion efficiency. Further GIWAXS studies have shown that the π–π stacking distance of BDTT-2DPPBFu small molecules is reduced and the inter-mixing of PC71BM within the BDTT-2DPPBFu-rich phase in the photo-active layer processed from 2.5 vol% CN is increased, leading to enhanced charge transport and reduced charge recombination and transfer resistance. The present work provides important progress in the nanomorphology of the photo-active layer, which can be effectively tuned via the use of a solvent additive in SM-OPVs.

We report the synthesis of a series of A1–π–A2–π–A1-type small molecules, DPP2T-RH, DPPFT-RH, and DPPT-RH, in which thiophene and furan were introduced to bridge the two strong electron-withdrawing units of DPP and rhodanine (RH). Interestingly, these DPP-RH-based small molecules exhibited ambipolar characteristics, showing photovoltaic performance both as donors and acceptors in combination with PC71BM and P3HT, respectively. The best power conversion efficiencies were obtained from DPPFT-RH (1.77%) and DPP2T-RH (1.28%) as donor and acceptor, respectively. Their physical properties, film packing ability, and photovoltaic performances were fine-tuned by rational design of the π-bridges.

We performed systematic experiments based on a small molecule donor and a polymer acceptor containing a naphthalene diimide (NDI)-based polymer as compared with fullerene-based acceptor (PC71BM) solar cells. Among polymer acceptors, the NDI-based polymer (PNDI-2T) shows good properties such as broad light absorbance with a strong absorption co-efficient and a well oriented crystalline structure leading to high electron mobility. We monitored the photovoltaic properties of both PNDI-2T and PC71BM acceptors with a BDT2TR donor. Although the BDT2TR:PC71BM device showed a higher PCE of 8.20%, the BDT2TR:PNDI-2T device also showed remarkable photovoltaic results with a PCE of 4.43%, VOC of 0.86 V, JSC of 7.26 mA cm−2, and FF of 71% indicating one of the highest efficiencies for small molecule donor and non-fullerene polymer acceptor systems. In particular, the PNDI-2T acceptor showed excellent thermal stability and intrinsic mechanical performance as compared with the PC71BM acceptor. To demonstrate the potential of the polymer acceptor for solar devices, we fabricated a device for testing thermal stability, high thickness tolerance, and the flexibility of the solar cell with bending stress. As a result, the PNDI-2T-based solar cell exhibited excellent thermal stability at 150 °C for 15 h and the PCE of the BDT2TR:PNDI-2T device with a thick active layer (around 610 nm) maintained 80% of its initial value. Moreover, the flexible device with the BDT2TR:PNDI-2T system retained its homogeneous morphology and showed maintained photovoltaic performance even after 100 bending cycles. Therefore, PNDI-2T based organic solar cells have good potential for application as flexible and portable real energy generators.

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.

A non-fullerene small molecule acceptor, SF-HR composed of 3D-shaped spirobifluorene and hexyl rhodanine, was synthesized for use in bulk heterojunction organic solar cells (OSCs). It possesses harmonious molecular aggregation between the donor and acceptor, due to the interesting diagonal molecular shape of SF-HR. Furthermore, the energy level of SF-HR matches well with that of the donor polymer, poly(3-hexyl thiophene) (P3HT) in this system which can affect efficient charge transfer and transport properties. As a result, OSCs made from a P3HT:SF-HR photoactive layer exhibited a power conversion efficiency rate of 4.01% with a high VOC of 1.00 V, a JSC value of 8.23 mA cm−2, and a FF value of 49%. Moreover, the P3HT:SF-HR film showed superior thermal and photo-stability to P3HT:PC71BM. These results indicate that SF-HR is specialized as a non-fullerene acceptor for use in high-performance OSCs.

Solution-processed organic solar cells (OSCs) and hybrid perovskite solar cells (PvSCs) generally require appropriate transparent electrode with a low work function, which improves the electron extraction, increases the built-in potential, and suppresses charge recombinations. Hence, interfacial modifiers between the cathode and the photoactive layer play a significant role in OSCs and PvSCs, as they provide suitable energy-level alignment, leading to desirable charge carrier selectivity and suppressing charge carrier recombinations at the interfaces. Here, we present a comprehensive study of the energy-level mapping between a transparent electrode and photoactive layers to enhance the electron-transport ability by introducing amine-based interfacial modifiers (ABIMs). Among the ABIMs, polyethylenimine ethoxylated (PEIE) incorporating inverted OSCs shows enhanced power conversion efficiencies (PCEs) from 0.32 to 9.83% due to large interfacial dipole moments, leading to a well-aligned energy level between the cathode and the photoactive layer. Furthermore, we explore the versatility of the PEIE ABIM by employing different photoactive layers with fullerene derivatives, a nonfullerene acceptor, and a perovskite layer. Promisingly, inverted nonfullerene OSCs and planar n-i-p PvSCs with PEIE ABIM show outstanding PCEs of 11.88 and 17.15%, respectively.

A series of small compound materials based on benzodithiophene (BDT) and diketopyrrolopyrrole (DPP) with three different alkyl side chains were synthesized and used for organic photovoltaics. These small compounds had different alkyl branches (i.e., 2-ethylhexyl (EH), 2-butyloctyl (BO), and 2-hexyldecyl (HD)) attached to DPP units. Thin films made of these compounds were characterized and their solar cell parameters were measured in order to systematically analyze influences of the different side chains of compounds on the film microstructure, molecular packing, and hence, charge-transport and recombination properties. The relatively shorter side chains in the small molecules enabled more ordered packing structures with higher crystallinities, which resulted in higher carrier mobilities and less recombination factors; the small molecule with the EH branches exhibited the best semiconducting properties with a power conversion efficiency of up to 5.54% in solar cell devices. Our study suggested that tuning the alkyl chain length of semiconducting molecules is a powerful strategy for achieving high performance of organic photovoltaics.

Two conjugated polymers based on dithienophosphole oxide, PBDT-O-DTPO and PBDT-T-DTPO, were synthesized. Two polymers were fairly soluble in chlorinated solvents, which is enough for device fabrication. According to the UV–vis spectra of films, PBDT-O-DTPO and PBDT-T-DTPO showed absorption onsets of 656 and 675 nm, correspond to optical band gaps of 1.89 and 1.84 eV, respectively. As the results, two polymers exhibited promising photovoltaic properties with power conversion efficiency (PCE) values of 2.23 and 2.53%, respectively, upon blending with PC71BM under AM 1.5 G illumination.

We studied fullerene-free organic solar cells based on electron-donating (BDT3TR) and -accepting (O-IDTBR) small molecules. Bulk heterojunction devices comprising BDT3TR:O-IDTBR showed an excellent power conversion efficiency exceeding 7% and much better thermal stability than BDT3TR:PC70BM devices after ageing at 120 °C for 300 hours.

Two novel polymers containing triple bonds in the backbone with different conjugation types (acceptor–acceptor and acceptor–donor structures) were synthesized and investigated for their crosslinking characteristics under UV irradiation. The crosslink formation was proven via UV-vis and IR spectroscopy, and it was found that the crosslinked polymers have solvent resistance properties during subsequent solvent washing with a similar solvent for the active layer. The two triple bond polymers were used as buffer layer materials to modify the interface properties of electron-selective ZnO in inverted PSCs via a spin-coating process. The effects of the buffer layer on the surface of the ZnO were studied via atomic force microscopy and contact angle measurements. The increased hydrophobic nature of the ZnO surface resulted in better contact with the active layer, and led to an improvement in the performance of the photovoltaic devices with increased fill factor (FF).

We report a systematic study of the role of introduced alkyl chains in the easily synthesized conjugated PDTT-ROBT copolymers, which consist of dithieno[3,2-b:2′,3′-d]thiophene (DTT) and alkoxy substituted benzothiadiazole (ROBT) subunits. We synthesized new conjugated polymers PDTT-BOBT and PDTT-HDBT, which have molecular structures similar to those of the previously reported PDTTDABT polymer, but have modified alkyl chains in the polymer backbone. The modifications of the alkyl chains from linear (PDTTDABT) to branched (PDTT-BOBT and PDTT-HDBT) had prominent effects on the solubility, crystallinity, molecular orientation and morphology of the co-polymers. Solar cell devices containing the new PDTT-BOBT and PDTT-HDBT polymers exhibited power conversion efficiency (PCE) values of 9.2% and 6.2%, respectively, considerably greater than the 2.2% PCE of the previously reported PDTTDABT polymer, and the 9.2% PCE is in fact the highest to date for donor–acceptor polymers containing the BTOR acceptor. This high PCE may be explained by the well-aligned energy levels, optimum film morphology with bicontinuous interpenetrating networks, enhanced charge carrier mobility and decreased amount of charge recombination that we observed for PDTT-BOBT, in contrast to those exhibited by PDTTDABT and PDTT-HDBT. Considering the potential of PDTT-BOBT for industrial application, we tested the scalability, large-area devices (6600 mm2) and stability of PDTT-BOBT. As a result, the PDTT-BOBT polymer with its easily synthesized structure and high efficiency has considerable potential for being synthesized on a large scale and for use in printable electronic applications.

Study on ultra-high-strength concrete(UHSC) has increased since it is essential in skyscraper construction. Since UHSC mixture has a large amount of the cementitious materials, UHSC can be applied on-site only when its thermal crack behavior due to heat of hydration is evaluated and controlled. In this study, finite element analysis using adiabatic temperature rise test data of UHSC was performed to evaluate thermal crack of UHSC columns. By modeling of circular and square UHSC columns, the characteristics of hydration heat, thermal stress, and thermal crack ratio were investigated according to column shape. As a result, it was confirmed that circular columns are more effective in thermal crack resistance than the square column.

The molecular self-organization of organic semiconductors, which is mainly determined by the structural design, film processing, and device configuration, is one of the crucial factors for achieving high-performance organic photovoltaics (OPVs) and perovskite solar cells (PvSCs). In this study, we newly synthesized and developed strongly self-organized small molecules via alkyl side-chain engineering. Replacing “H” to “C6H13” on the thienyl group, SM2 showed a well-ordered face-on orientation. Due to favorable self-organization leading to effective charge carrier dynamics, including enhanced charge transfer/transport and suppressed recombination, SM2-based OPVs and PvSCs exhibited improved device performance compared to the devices based on SM1 without an additional hexyl side-chain. The best fullerene-based OPV and planar PvSC with SM2 as a small-molecule donor and as a hole transport layer (HTL) achieved an unprecedentedly high efficiency of 9.38% and 20.56%, in contrast with SM1-based devices showing lower efficiency of 8.70% and 15.37%. Furthermore, the planar PvSCs based on undoped-SM2 HTL exhibited comparable efficiency but provided excellent heat and humidity stability compared with doped spiro-OMeTAD-based devices. These results clearly indicated that SM2 with highly-ordered and favorable self-organization is a promising organic semiconductor for future applications of high-performance organic and inorganic-organic hybrid electronics.

A fluorinated BDT-TPD-based donor polymer (P1) was synthesized via Suzuki polymerization. P1 shows a wide bandgap (1.9 eV) and a deep highest occupied molecular orbital level (−5.71 eV). Ternary organic solar cells (OSCs) were fabricated from our synthesized polymer donor (P1) and two small molecular nonfullerene acceptors (IT-4F and Y6). The P1:IT-4F binary OSC exhibited a power conversion efficiency (PCE) of 6.59%, with a short-circuit current density (JSC) of 10.36 mA/cm2, open-circuit voltage (VOC) of 0.91 V and a fill factor (FF) of 70%. By contrast, the P1:Y6 binary OSC exhibited a PCE of 10.58% with a JSC of 22.01 mA/cm2, VOC of 0.86 V and FF of 56%. An enhanced PCE of 11.64% was achieved in the ternary OSC with 25 wt% IT-4F incorporated into the acceptors [IT-4F:Y6 (25:75)]; this enhancement was attributed to the improved JSC of 22.97 mA/cm2, VOC of 0.87 V and FF of 58%. Appropriate phase separation could be achieved by incorporating an appropriate amount of IT-4F into the acceptors, which promoted exciton dissociation and charge transport. The PCE improvement of the IT-4F:Y6 (25:75) ternary device was attributed mainly to enhanced photon harvesting and exciton dissociation and to reduced charge recombination.

Dithieno[3,2-b:2',3'-d]thiophene (DTT) has emerged as an important building block in the synthesis of a wide variety of optoelectronic materials. Two new DTT containing conjugated polymers, poly(dithieno[3,2-b:2',3'-d]thiophenevinylene-alt-9,9-diethylhexyl-2,7-fluorenediyl vinylene) (FLU-DTT) and poly(dithieno[3,2-b:2',3'-d]thiophenevinylene-alt-2-methoxy-5-(2-ethylhexyloxy)-p-phenylenevinylene) (MEH-DTT), were designed and synthesized. The photoluminescence (PL) spectra of FLU-DTT and MEH-DTT in film exhibit maximum emission peaks at 538 and 602 nm, respectively. The MEH-DTT polymer film showed far more red-shifted maximum electroluminescene (EL) emission at 650 nm. The photovoltaic device was also fabricated using MEH-DTT and PC71BM as active layer and it showed power conversion efficiency (PCE) for the polymer solar cell (PSC) as 0.59% under AM 1.5 G (100 mW/cm2) conditions.

Two thieno[3,4-c]pyrrole-4,6-dione (TPD)-based copolymers, poly[5,10-bis(2-ethylhexyloxy) naphtho[1,2-b:5,6-b’]dithiophene-2,7-diyl-alt-1,3-(5-heptadecan-9-yl)-4H-thieno[3,4-c]pyrrole-4,6-dione] (P1) and poly[4,9-bis(2-ethylhexyloxy)naphtho[1,2-b:5,6-b’]dithiophene-2,7-diyl-alt-1,3-(5-heptadecan-9-yl)-4H-thieno[3,4-c]pyrrole-4,6-dione] (P2), were synthesized and used as donor materials in polymer solar cells (PSCs). The optical, electrochemical, and photovoltaic properties of the copolymers were investigated. Under optimized conditions, the TPD-based polymers showed power conversion efficiencies (PCEs) for the PSCs in the range from 1.1 to 2.1% under AM 1.5 illumination (100 mW/cm2).

Two benzo[1,2-b:4,5-b’]dithiophene (BDT)-based copolymers, poly[4,8-bis(5-(2-ethylhexyl) thiophene-2-yl)benzo[1,2-b:4,5-b’]dithiophene-alt-5,8-(2,3-bis(4-octyloxy)phenyl)quinoxaline] (P1) and poly[4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b:4,5-b’]dithiophene-alt-5,7-(2,3-bis(4- octyloxy)phenyl)thieno[3,4-b]pyrazine] (P2), are synthesized and used as donor materials in polymer solar cells (PSCs). To obtain a low band gap polymer, we use a copolymerized donor-acceptor structure. The optical, electrochemical, and photovoltaic properties of the copolymers are investigated. The results indicate that the acceptor units in the copolymers influenced the band gap, electronic energy levels, and photovoltaic properties of the copolymers significantly. The band gaps of the copolymers are in the range 1.34 − 1.75 eV. Under optimized conditions, the BDT-based polymers showed power conversion efficiencies (PCEs) for the PSCs in the range 1.46 − 2.05% under AM 1.5 illumination (100 mW/cm2).

Two donor–acceptor conjugated polymers, PTSSO-TT and PTSSO-BDT, composed of acenaphtho[1,2-c]thiophene-S,S-dioxide (TSSO) as a new electron acceptor and thienothiophene (TT) or benzo[1,2-b:4,5-b']dithiophene (BDT) as electron donors, were synthesized with Stille cross-coupling reactions. The number-averaged molecular weights (Mn) of PTSSO-TT and PTSSO-BDT were found to be 15100 and 26000 Da, with dispersity of 1.8 and 2.4, respectively. The band-gap energies of PTSSO-TT and PTSSO-BDT are 1.56 and 1.59 eV, respectively. The HOMO levels of PTSSO-TT and PTSSO-BDT are −5.4 and −5.5 eV, respectively. These results indicate that the inclusion of TSSO accepting units into polymers is a very effective method for lowering their HOMO energy levels. The field-effect mobilities of PTSSO-TT and PTSSO-BDT were determined to be 1.5 × 10−3 and 4.5 × 10−4 cm2 V−1 s−1, respectively. A polymer solar cell device prepared with PTSSO-TT as the active layer was found to exhibit a power conversion efficiency (PCE) of 3.79% with an open circuit voltage of 0.71 V under AM 1.5 G (100 mW cm−2) conditions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015

A series of new conjugated polymers based on the asymmetric benzo[1,2-b:4,5-b′]dithiophene (BDT) unit were designed and synthesized for use in bulk-heterojunction polymer solar cells. Each side chain of the BDT was tuned by introducing alkyl and alkoxy groups. The best solar cell efficiency was achieved in an asymmetric polymer device based on 4-octyl-8-octyloxy-BDT (7.64% PCE), which performed better than devices based on the symmetric dioctyl-BDT (6.48% PCE) or dioctyloxy-BDT (7.18% PCE). Further modification of the side chains, replacing octyloxy with butoxydiethoxy, improved the PCE to 8.12% due to the enhanced hole mobility, hole/electron mobility balance, and formation of tight contacts with the PEDOT:PSS layer. The effects of the side chains on the polymer HOMO energy levels and photovoltaic parameters were investigated.

We synthesized and characterized a series of pyrene units incorporated into benzo[1,2-b:4,5-b′]dithiophene-based random copolymers. Concentration-dependent pyrene-driven self-assembly in the copolymers was systematically investigated using measurements of the copolymer optical and electrochemical properties, the hole mobilities extracted from the field-effect transistor and the space charge limited current, and the photovoltaic characteristics. We additionally studied the morphological changes using differential scanning calorimetry (DSC), synchrotron X-ray diffraction analysis, AFM, and TEM. The Py–Py interactions were found to facilitate the formation of fibrous structures. As the Py content increased, multiple Py–Py interactions within a few polymer chains dominated the interchain interactions to produce a more ordered phase but less interconnectivity among many polymer chains. A threshold quantity of the Py moieties enabled the Py–Py interactions to propagate over many polymer chains to form a highly ...

A series of donor-rich semi-random copolymers with various benzodithiophene (donor unit)/fluorinated-thienothiophene (acceptor unit) ratios – D2A, D3A, D5A, D7A – were designed and synthesized for use in polymer solar cells (PSCs). The polymer D1A was also synthesized for comparison. The optical and electrochemical properties of these polymers vary with the number of donor units in their polymer backbones. The device containing the polymer D5A exhibits a best power conversion efficiency (PCE) of 5.52% when the active layer thickness is 340 nm, a value that is 80% of its maximum PCE, whereas the best PCE of the D1A-based device is reduced by 32% when the active layer thickness is 310 nm. A large area (6,270 mm 2 ) D5A-based device prepared with the slot die-coating method was found to exhibit a best PCE of 6.54%, which is significantly better than that of the equivalent D1A-based large area device (4.03%).

A series of four donor-acceptor alternating copolymers based on dialkyloxy-benzothiadiazole (ROBT) as an acceptor and thienoacenes as donor units were synthesized and tested for polymer solar cells (PSCs). These new polymers had different donor units with varied electron-donating ability (thieno[3,2-b]thiophene (TT), dithieno[3,2-b:2',3'-d]thiophene (DTT), benzo[1,2-b:4,5-b']dithiophene (BDT), and naphtha[1,2-b:5,6-b']dithiophene (NDT)) in the polymer backbone. To understand the effect of these thienoacenes on the optoelectronic and photovoltaic properties of the copolymers, we systematically analyzed and compared the energy levels, crystallinity, morphology, charge recombination, and charge carrier mobility in the resulting polymers. In this series, optimized photovoltaic cells yielded power conversion efficiency (PCE) values of 6.25% (TT), 9.02% (DTT), 6.34% (BDT), and 2.29% (NDT) with different thienoacene donors. The introduction of DTT into the thienoacene-ROBT polymer enabled the generation of well-ordered molecular packings with a π-π stacking distance of 3.72 Å, high charge mobilities, and an interconnected nanofibrillar morphology in blend films. As a result, the PSC employing the polymer with DTT exhibited the highest PCE of 9.02%. Thus, our structure-property relationship studies of thienoacene-ROBT-based polymers emphasize that the molecular design of the polymers must be carefully optimized to develop high efficient PSCs. These findings will help us to understand the impact of the donor thienoacene on the optoelectronic and photovoltaic performance of polymers.