Nanoblends of Incompatible Polymers by Direct Space-Confined Polymerization

Nanoblends of Incompatible Polymers by Direct Space-Confined Polymerizatio

Highly Efficient P3HT: C60 Solar Cell Free of Annealing Process

All conjugated C60-containing block copolymers (BCPs) based on quasi-living Grignard metathesis (GRIM) polymerization have been designed and synthesized for application in polymer solar cells (PSCs). The C60-containing BCP can induce the formation of a self-organization nanostructure of P3HT domain. Moreover, this C60-containing BCP serves as a compatibilizer to reduce the interfacial tension between the P3HT and C60, thus help establishing a moderate phase-separated morphology with crystalline P3HT and C60 domain. The performance up to 2.56%(AM 1.5G irradiation (100 mW/cm2)) of a P3HT:C60 device can be achieved by using C60–BCP as additive without any post-treatment

Low-Bandgap Poly(Thiophene-Phenylene-Thiophene) Derivatives with Broaden Absorption Spectra for Use in High-Performance Bulk-Heterojunction Polymer Solar Cells

Two low-bandgap (LGB) conjugated polymers (P1 and P2) based on thiophene-phenylene-thiophene (TPT) with adequate energy levels have been designed and synthesized for application in bulk-heterojunction polymer solar cells (PSCs). The absorption spectral, electrochemical, field effect hole mobility and photovoltaic properties of LGB TPT derivatives are investigated and compared with poly(3-hexylthiophene) (P3HT). Photophysical studies reveal bandgaps of 1.76 eV for P1 and 1.70 eV for P2, which could effectively harvest broader solar spectrum. In addition, the thin film absorption coefficients of P1 and P2 are 1.6 × 105 cm−1 (λ ≈ 520 nm) and 1.4 × 105 cm−1 (λ ≈ 590 nm), respectively. Electrochemical studies indicate desirable HOMO/LUMO levels that enable a high open circuit voltage while blending them with fullerene derivatives as electron acceptors. Furthermore, both materials show sufficient hole mobility (3.4 × 10−3 cm2/Vs for P2) allowing efficient charge extraction and a good fill-factor for PSC application. High-performance power conversion efficiency (PCE) of 4.4% is obtained under simulated solar light AM 1.5 G (100 mW/cm2) from PSC device with an active layer containing 25 wt% P2 and 75 wt% [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), which is superior to that of the analogous P3HT cell (3.9%) under the same experimental condition

Thiophene/Phenylene/Thiophene-Based Low-Bandgap Conjugated Polymers for Efficient Near-Infrared Photovoltaic Applications

We have prepared thiophene/phenylene/thiophene (TPT)-based low bandgap conjugated polymers exhibiting tunable energy levels and investigated their application in solar cells. By incorporating various electron-withdrawing comonomers through Stille coupling reactions, we obtained TPT-based donor/acceptor copolymers having bandgaps ranging from 1.0 to 1.8 eV. We compared the absorption spectra, electrochemistry, field effect hole mobility, and photovoltaic properties of these low bandgap TPT derivatives with those of poly(3-hexylthiophene) (P3HT). The absorption coefficients of the thin films fell in the range from 0.77 × 105 to 1.4 × 105 cm−1. These materials displayed sufficiently high hole mobilities (>10−3 cm2 V−1 s−1) for efficient charge extraction and good fill-factors for organic photovoltaic applications. Electrochemical studies indicated desirable HOMO/LUMO levels, with a good correlation between the HOMO energy levels and the open circuit voltage (Voc) when the polymers were blended with fullerene derivative as an electron acceptor. Power conversion efficiencies of up to 4.3% were achieved under AM 1.5G simulated solar light (100 mW cm−2). Our findings suggest that TPT derivatives presenting suitable electron-withdrawing groups are promising photovoltaic materials

Dimeric and Cyclotrimeric Piano-Stool Vanadium(III) Dihalides with Unusual Differences in V−V Distance and Magnetochemistry. Syntheses, Structures, and Reactivities of (η-C₅Me₄R)₂V₂(μ-Br)₄ and the Trivanadium Cluster (η-C₅Me₄R)₃V₃(μ-Cl)₆, New Mid-Valent Organovanadium Synthons

Reductive oligomerization of (C5Me4R)VX3 or addition of (C5Me4R)SnBu3 to VX3L3 (L = thf, tht) yields the (peralkylcyclopentadienyl)vanadium(III) halides (η5-C5Me4R)2V2(μ-Br)4 and (η5-C5Me4R)3V3(μ-Cl)6 (R = Me, Et), which can be halogenated to afford (C5Me4R)VX3. Paramagnetic (C5Me4Et)2V2(μ-Br)4 is a four-legged piano-stool dimer in the solid state with a nominal V−V bond (2.565(1) Å), while the spin-frustrated, antiferromagnetic (C5Me4Et)3V3(μ-Cl)6 is a piano-stool cyclotrimer with two μ-chlorines per nonbonded V···V edge (3.3732[63] Å)

New Two-Dimensional Thiophene−Acceptor Conjugated Copolymers for Field Effect Transistor and Photovoltaic Cell Applications

We report the synthesis, properties, and optoelectronic device applications of two-dimensional (2D) like conjugated copolymers, P4TBT, P4TDTBT, P4TDTQ, and P4TDPP, consisting of 2′,5′′-bis(trimethystannyl)-5,5′′′-di-(2-ethylhexyl)[2,3′;5′,2′′;4′′,2′′′]quarterthiophene (4T) with the following four acceptors of 4,7-dibromo-2,1,3-benzothiodiazole (BT), 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTBT), 2,3-bis(4-(2-ethylhexyloxy)phenyl)-5,8-bis[5′-bromodithien-2-ylquinoxalines] (DTQ), and 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP). The optical band gaps (eV) of the studied conjugated copolymers are in the order of P4TDPP (1.29) P4TDTBT (1.60) P4TDTQ (1.83) (1.88). The 2D-like conjugated copolymers exhibited high field effect (FET) hole mobilities in the range of 10−1−10−4 cm2 V−1 s−1. On the other hand, the FET electron mobilities were observed for P4TDTBT and P4TDPP because of their relatively low-lying LUMO level suitable for electron injection. In particular, P4TDPP showed the ambipolar characteristics with the hole and electronic mobilities of 0.115 cm2 V−1 s−1 (on/off ratio: 2.49 × 104) and 3.08 × 10−3 cm2 V−1 s−1 (on/off ratio: 7.34 × 102), respectively, which was strongly related to its ordered intermolecular chain packing based on the DSC and XRD results. The power conversion efficiencies (PCE) of the prepared polymer/PC71BM (1:3) based photovoltaic cells were in the range 1.28−1.67% under the illumination of AM 1.5G (100 mW/cm2). The PCE could be enhanced up to 2.43% of the P4TDPP/PC71BM (1:2) based device because of the balanced hole/electron mobility. The above results indicate that these two-dimensional 4T−acceptor conjugated copolymers could enhance the charge-transport characteristics and are promising materials for organic optoelectronic devices

Synthesis of New Indolocarbazole-Acceptor Alternating Conjugated Copolymers and Their Applications to Thin Film Transistors and Photovoltaic Cells

We report synthesis, properties, and optoelectronic device characteristics of six new indolocarbazole−acceptor conjugated copolymers prepared by Suzuki coupling reaction. Two different linkages of indolocarbazole (28IC and 39IC) and four acceptors of 2,3-didodecylthieno[3,4-b]pyrazine (TP12), 2,3-bis(4-(2-ethylhexyloxy) phenyl)thieno[3,4-b]pyrazine (TPO), 2,1,3-benzothiadiazole (BT), and 2,3-bis(4-(2-ethylhexyloxy)phenyl)quinoxaline (QO) were used to explore the effects of acceptor structure, linkage, and side group on the electronic and optoelectronic properties. The optical band gap (eV) of the studied copolymers were in the following order: P28IC-TPO (1.58) P39IC-TP12 (1.79) P28IC-TP12 (1.84) (2.09) P28IC-QO (2.31) P39IC-QO (2.34). The hole mobility and on−off ratios of the studied copolymers were in the ranges 1.66 × 10−5 to 4 × 10−4 cm2/V·s and 40−46900, respectively. It basically depended on the degree of intromolecular charge transfer between indolocarbazole and acceptor as well as the HOMO level. The power conversion efficiency (PCE) of the indolocarbazole−acceptor polymer/PC61BM or PC71BM based photovoltaic cells were in the range 0.14−1.40% under the illumination of AM 1.5G (100 mW/cm2). P28IC-QO showed the best PCE among the studied copolymers because of its suitable HOMO/LUMO energy level, high molecular weight, good hole mobility, efficient PL quenching, and large Voc

Morphology Evolution of Spin-Coated Films of Poly(thiophene−phenylene−thiophene) and [6,6]-Phenyl-C₇₁-butyric Acid Methyl Ester by Solvent Effect

This paper describes the influence of the solvent on the morphological evolution and performance of polymer solar cells (PSCs) based on blended films of poly(thiophene−phenylene−thiophene) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The blends are spin-coated with solvents exhibiting various evaporation rates, including o-dichlorobenzene (DCB), chlorobenzene (CB), chloroform (CF), and tetralin. The changing morphologies of these blended films are monitored using atomic force microscopy (AFM) and transmission electron microscopy (TEM). A solvent having a higher boiling point [1,8-octanedithiol (OT)] is also introduced as an additive to further fine-tune the morphology of the bulk heterojunction (BHJ). We demonstrate herein that the morphology of a blendand, hence, the performance of a BHJ devicecan be manipulated by controlling the rate of solvent evaporation during film formation. The resulted fine-scale phase separation leads to enhanced performance of such organic photovoltaic devices. The highest power efficiency for our PSCs (5.8%, AM 1.5G irradiation (100 mW/cm2)) resulted when we use DCB as the solvent with OT as a processing additive