Highly efficient dye sensitized solar cells based on a novel ruthenium sensitizer

A new sensitizer, Ru(2,2′-bipyridine-4,4′-dicarboxylic acid)-4,4′-bis(2-(4-N,N′-diphenylaminophenyl)ethenyl)-2,2′-bipyridine) (NCS)₂, denoted K77-7, was synthesized. The UV–vis spectrum of K77-7 was characterized. Dye sensitized solar cells (DSSC) based on K77-7 were fabricated and devices J/V curves were measured. The effects of co-adsorbent chenodeoxycholic acid, solvent in electrolyte, TiO₂ light scattering layer, and treatment of TiCl₄ aqueous solution on device efficiency were discussed. Under solar illumination of 100 mW cm^?2 (A.M. 1.5), the optimized DSSC device efficiency of 10.1 % was obtained.     

The effects of co-sensitization in dye-sensitized solar cells

Triazoloisoquinoline-based organic dyestuff was synthesized and used in the fabrication of dye-sensitized solar cells (DSSCs). After co-sensitization with ruthenium complex, triazoloisoquinoline-based organic dyestuff overcomes the deficiency of ruthenium dyestuff absorption in the blue part of the visible spectrum. The incident photon-to-electron conversion efficiency (IPCE) of cis-dithiocyanate-N,N′-bis-(4-carboxylate-4-tetrabutyl ammoniumcarboxylate-2,2′-bipyridine)ruthenium(II) (N719) at shorter wavelength regions (~350–500 nm) is 35 %. After addition of triazoloisoquinoline-based dyestuff for co-sensitization, the IPCE at 350–500 nm increased significantly. This can be attributed to the increased photocurrent of the cells, which improves the dye-sensitized photoelectric conversion efficiency. After optimization of the cells, an energy conversion efficiency of 8.83 % was achieved using an 12 + 4 μm TiO₂ electrode, under simulated solar illumination (AM 1.5G). As a consequence, this low molecular weight organic dyestuff is a promising candidate as a co-adsorbent and co-sensitizer for highly efficient DSSCs.     

Synthesis and photovoltaic properties of new near infrared absorption polymers based on C and N-bridged dithiophene and diketopyrrolopyrrole units

Two novel diketopyrrolopyrrole-based conjugated copolymers, namely, poly{[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl]-alt-[3,6-bis(bithiophen-5-yl)-2,5-di-(2-ethylhexyl)-pyrrolo[3,4-c]pyrrole-1,4-dione]} (P1) and poly{[N-(2-ethylhexyl)-dithieno[3,2-b:2′,3′-d]pyrrole-2,6-diyl]-alt-[3,6-bis(bithiophen-5-yl)-2,5-di-(2-ethylhexyl)-pyrrolo[3,4-c]pyrrole-1,4-dione]} (P2), have been designed and synthesized by Stille coupling reaction. The resulting copolymers exhibited very broad and strong absorptions in the visible and near-infrared region. Through cyclic voltammetry measurements, it was found that P1 possesses a lower highest occupied molecular orbital energy level (?5.14 eV) compared to that of P2 (?4.98 eV). The bulk heterojunction photovoltaic devices were fabricated by using the two copolymers as the donor and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) as the acceptor in the active layer. The maximum power conversion efficiency of 1.48 % was obtained based on the blend of P1:PCBM = 1:3(w/w) with open circuit voltage (V _OC ) of 0.66 V and short circuit current (J _SC ) of 6.36 mA/cm², under the illumination of AM 1.5, 100 mW/cm².     

Properties of pulse electrodeposited copper gallium sulphide films

Copper gallium sulphide films were deposited for the first time by the pulse electrodeposition technique at different duty cycles in the range of 6–50 % at room temperature and at a constant current density of 1.0 mA cm^?2. The films exhibited single phase copper gallium sulphide. The grain size increased from 30 to 70 nm with increase of duty cycle. Optical band gap of the films varied in the range of 2.30–2.36 eV. The resistivity increased from 0.10 to 1.70 ohm cm with increase of duty cycle from 6 to 50 %. Preliminary studies on solar cells with p-CuGaS₂/n-CuInS₂ junction yielded an efficiency of 4.14 %. This is the first report on solar cells using CuGaS₂ with CuInS₂.     

Synthesis,nonlinear optical properties and cellular imaging of hybrid ZnS nanoparticles capped with conjugated terpyridine derivatives

A novel organic/inorganic nanohybrids which consisted of ligand L (L = 2-[(2-hydroxy-ethyl)-(4-[2,2′;6′,2″] terpyridin-4′-yl-phenyl)-amino]-ethanol), an optical terpyridine derivative and ZnS nanoparticles (NPs), had been prepared through a solution-phase synthesis technique. The intermolecular interactions at the interface between ZnS and the ligand components were analyzed by FT-IR, far-IR, UV–Vis absorption spectroscopy, XRD and TEM. Particular properties had been shown by fluorescence spectra, fluorescence lifetime, Raman spectrum, aggregation emission and non-linear optical response. The results indicated that the nano-composite L–ZnS NPs had an obvious aggregation-induced emission in ethanol/n-hexane mixtures, and had larger two-photon absorption (TPA) when compared to the free ligand L. The data for the TPA cross-section value (σ = 16,247.8 GM), nonlinear refractive index (γ = 4.46 × 10^?13 cm² W^?1) and the third order nonlinear polarizability [Imχ ⁽³⁾ (esu) = 1.13 × 10^?14] were measured and discussed. Meanwhile, due to the laser irradiation induced charge transfer from the ligand to ZnS NPs, the composite could be potentially applied in vitro and in vivo cellular imaging.     

Rutile TiO<Subscript>2</Subscript> films as electron transport layer in inverted organic solar cell

Titanium dioxide (TiO₂) thin films were prepared by sol–gel spin coating method and deposited on ITO-coated glass substrates. The effects of different heat treatment annealing temperatures on the phase composition of TiO₂ films and its effect on the optical band gap, morphological, structural as well as using these layers in P3HT:PCBM-based organic solar cell were examined. The results show the presence of rutile phases in the TiO₂ films which were heat-treated for 2 h at different temperatures (200, 300, 400, 500 and 600 °C). The optical properties of the TiO₂ films have altered by temperature with a slight decrease in the transmittance intensity in the visible region with increasing the temperature. The optical band gap values were found to be in the range of 3.28–3.59 eV for the forbidden direct electronic transition and 3.40–3.79 eV for the allowed direct transition. TiO₂ layers were used as electron transport layer in inverted organic solar cells and resulted in a power conversion efficiency of 1.59% with short circuit current density of 6.64 mA cm^?2 for TiO₂ layer heat-treated at 600 °C.     

Synthesis and characterization of novel 2,7-carbazole derivatives for blue light-emitting diodes

Two 2,7-carbazole based low molecular weight derivatives, 9-hexyl-N ²,N ²,N ⁷,N ⁷-tetraphenyl-carbazole-2,7-diamine (TPCA) and 9′-hexyl-9′H-9,2′:7′,9″-tercarbazole (HTC), were synthesized by Buchwald and Ullmann coupling reactions, respectively. The optical, electrochemical and thermal properties of this two analogous small molecule hosts have been characterized. The HOMO level of TPCA and HTC were ?5.25 and ?5.29 eV indicating good hole-transporting properties. Both of the compounds emit deep blue light peaked at 410 and 428 nm in solid state. According to the measurement, the luminescence quantum yield of TPCA is 0.98, almost 1.7 times higher than that of HTC (0.59) in dilute THF solution. The geometrical and electronic properties of the compounds were studied using density functional theory calculations. The studies mentioned above indicate that both TPCA and HTC are suitable for active materials of blue light-emitting diodes.     

A solution-processable D–A–D small molecule based on isoindigo for organic solar cells

A new linear D–A–D organic small molecule (M1), with triphenylamine as electron donor (D) unit and isoindigo (ID) as electron acceptor (A) unit, was synthesized by Stille coupling reactions. It exhibits broad and strong absorption (300–700 nm), a relatively low HOMO energy level (?5.30 eV), low band gap (1.69 eV), and moderate hole mobility (2.49×10^?4 cm²/Vs). Solution-processed small molecule bulk-heterojunction solar cells based on M1: PC₆₁BM (1:3, w/w) blend film exhibits a power conversion efficiency of 0.84 % with an open-circuit voltage (V _oc) of 0.78 V, under the illumination of AM1.5, 100 mW/cm².     

Indium rich InGaN solar cells grown by MOCVD

This study focuses on both epitaxial growths of In_xGa_1?xN epilayers with graded In content, and the performance of solar cells structures grown on sapphire substrate by using metal organic chemical vapor deposition. The high resolution X-ray and Hall Effect characterization were carried out after epitaxial InGaN solar cell structures growth. The In content of the graded InGaN layer was calculated from the X-ray reciprocal space mapping measurements. Indium contents of the graded InGaN epilayers change from 8.8 to 7.1 % in Sample A, 15.7–7.1 % in Sample B, and 26.6–15.1 % in Sample C. The current voltage measurements of the solar cell devices were carried out after a standard micro fabrication procedure. Sample B exhibits better performance with a short-circuit current density of 6 mA/cm², open-circuit voltage of 0.25 V, fill factor of 39.13 %, and the best efficiency measured under a standard solar simulator with one-sun air mass 1.5 global light sources (100 mW/cm²) at room temperature for finished devices was 0.66 %.     

A Tandem Organic Solar Cell with PCE of 14.52% Employing Subcells with the Same Polymer Donor and Two Absorption Complementary Acceptors

The tandem structure is an efficient way to simultaneously tackle absorption and thermalization losses of the single junction solar cells. In this work, a high‐performance tandem organic solar cell (OSC) using two subcells with the same donor poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBDB‐T) and two acceptors, F‐M and 2,9‐bis(2‐methylene‐(3(1,1‐dicyanomethylene)benz[f ]indanone))7,12‐dihydro‐(4,4,10,10‐tetrakis(4‐hexylphenyl)‐5,11‐diocthylthieno[3′,2′:4,5]cyclopenta[1,2‐b]thieno[2″,3″:3′,4′]cyclopenta[1′,2′:4,5]thieno[2,3‐f][1]benzothiophene (NNBDT), with complementary absorptions is demonstrated. The two subcells show high V_oc with value of 0.99 V for the front cell and 0.86 V for the rear cell, which is the prerequisite for obtaining high V_oc of their series‐connected tandem device. Although there is much absorption overlap for the subcells, a decent J_sc of the tandem cell is still obtained owing to the complementary absorption of the two acceptors in a wide range. With systematic device optimizations, a best power conversion efficiency of 14.52% is achieved for the tandem device, with a high V_oc of 1.82 V, a notable FF of 74.7%, and a decent J_sc of 10.68 mA cm^?2. This work demonstrates a promising strategy of fabricating high‐efficiency tandem OSCs through elaborate selection of the active layer materials in each subcell and tradeoff of the V_oc and J_sc of the tandem cells.     

Thiophene‐Bridged Donor–Acceptor sp2‐Carbon‐Linked 2D Conjugated Polymers as Photocathodes for Water Reduction

Photoelectrochemical (PEC) water reduction, converting solar energy into environmentally friendly hydrogen fuel, requires delicate design and synthesis of semiconductors with appropriate bandgaps, suitable energy levels of the frontier orbitals, and high intrinsic charge mobility. In this work, the synthesis of a novel bithiophene‐bridged donor–acceptor‐based 2D sp²‐carbon‐linked conjugated polymer (2D CCP) is demonstrated. The Knoevenagel polymerization between the electron‐accepting building block 2,3,8,9,14,15‐hexa(4‐formylphenyl) diquinoxalino[2,3‐a:2′,3′‐c]phenazine (HATN‐6CHO) and the first electron‐donating linker 2,2′‐([2,2′‐bithiophene]‐5,5′‐diyl)diacetonitrile (ThDAN) provides the 2D CCP‐HATNThDAN (2D CCP‐Th). Compared with the corresponding biphenyl‐bridged 2D CCP‐HATN‐BDAN (2D CCP‐BD), the bithiophene‐based 2D CCP‐Th exhibits a wide light‐harvesting range (up to 674 nm), a optical energy gap (2.04 eV), and highest energy occupied molecular orbital–lowest unoccupied molecular orbital distributions for facilitated charge transfer, which make 2D CCP‐Th a promising candidate for PEC water reduction. As a result, 2D CCP‐Th presents a superb H₂‐evolution photocurrent density up to ≈7.9 µA cm^?2 at 0 V versus reversible hydrogen electrode, which is superior to the reported 2D covalent organic frameworks and most carbon nitride materials (0.09–6.0 µA cm^?2). Density functional theory calculations identify the thiophene units and cyano substituents at the vinylene linkage as active sites for the evolution of H₂.     

Photoluminescence characteristics of synthesized copper doped Cd1−x Zn x S quantum dots

Free standing powders of copper-doped Cd_1?x Zn _x S (0 ≤ x ≤ 0.5) quantum dots (QDs) were synthesized using a simple chemical co-precipitation method. The copper concentration was varied from 0.01 to 10 at. wt% of Cd²⁺. X-ray diffraction and transmission electron microscope were used for crystallographic and morphological analyzes. Room temperature time resolved luminescence spectra were recorded using high peak power, pulsed N₂-laser excitation. Decay time values for bluish green and yellow emission have been calculated from recorded luminescence decay curves. Decay time dependence on Cu²⁺ and Zn²⁺ concentrations have been studied in detail. These QDs will have wide applications as nanophosphors, solar cells, photocatalysts and chemical sensors.     

Crystal structure and thermal annealing behaviors of high d 33 Aurivillius-phase ceramics Li0.04Ce0.04Na(0.46−x/2)Bi(4.46+x/2)Ti(4−x)Sc x O15 with the Sc3+/Bi3+ co-substitution

Modified Aurivillius-type-structured piezoelectric ceramics, Li_0.04Ce_0.04Na_(0.46?x/2)Bi_(4.46+x/2)Ti_(4?x)Sc _x O₁₅ (LiCe–NBT–Sc?x, x = 0, 0.025, 0.075, 0.125, 0.15, 0.175) were synthesized by using conventional solid-state reaction process. Rietveld refinement for the x = 0.125 modified sample was carried out by using powder X-ray diffraction and LiCe–NBT–Sc?0.125 was confirmed to be a four-layer Aurivillius oxide with orthorhombic space group A2 ₁ am [a = 5.45814(7) Å, b = 5.43029(7) Å, c = 40.8547(4) Å and V = 1,210.902(26) Å³; Z = 4], at room temperature. The Sc³⁺/Bi³⁺ substitution led to an increase in Curie temperatures (T _c) and an enhancement in piezoelectric property, and the LiCe–NBT–Sc?0.125 ceramic with a T _c of 675 °C had a high piezoelectric activity (d ₃₃) of 32 pC/N. Variable thermal-annealing d ₃₃ and resistivity (ρ) of the LiCe–NBT–Sc?0.125 ceramic were investigated; the d ₃₃ of the O₂ annealed sample reached up to 37 pC/N, and its resistivity was about 6.8 × 10⁶ Ω cm at 575 °C and about 6.5 × 10⁵ Ω cm at 650 °C.     

Synthesis of organ-soluble copolyimides by one-step polymerization and fabrication of high performance fibers

A series of organ-soluble copolyimides (co-PIs) were synthesized from 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 2,2′-bis(trifluoromethyl)-4, 4′-diaminobiphenyl (TFMB), and 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) via a one-step polymerization in N-methyl-2-pyrrolidone (NMP). The polyimide solutions were used to fabricate as-spun polyimide fiber by a wet-spinning process. SEM images of the round cross-section of the fibers indicated that a homogeneous and dense fibrous structure was produced in the coagulation bath of H₂O/NMP = 90/10 (v/v) and many microfibrils appeared on the surface. The drawn fibers exhibit excellent mechanical properties, and the strength and modulus of BTDA/TFMB/BIA co-PI fibers (TFMB/BIA = 50/50) reached 2.25 and 102 GPa with a draw ratio of 3.0. The 5 % weight loss temperature of the co-PI fibers in thermogravimetric analysis spectra achieved 548–563 °C in an air atmosphere. The glass transition temperatures were found to be between 340 and 366 °C according to the DMA results. Annealed BTDA/TFMB/BIA co-PI fibers displayed distinct wide-angle X-ray patterns, and crystallinity and crystal orientation with various draw ratios were observed.     

Cu content dependence of Cu<Subscript>2</Subscript>Zn(SnGe)Se<Subscript>4</Subscript> solar cells prepared by using sequential thermal evaporation technique of Cu/Sn/Cu/Zn/Ge stacked layers

The doping of Cu₂ZnSnSe₄ semiconductor with Ge element has demonstrated improvements to kesterite solar cell efficiency. However, the impact of different Cu concentrations on Cu₂ZnSnGeSe₄/CdS solar cell performance has been poorly studied. In this work, Cu₂ZnSnGeSe₄ thin films with different Cu contents were synthesized by selenization of sequential thermal evaporation precursors. Solar cells based on kesterite-type Cu₂ZnSnGeSe₄ (CZTGSe) were fabricated and the influence of the Cu thickness on the chemical composition and morphology of the layers and electro-optical properties of solar cells was studied. The stacking process was performed at room substrate temperature. Efficiency values in the range of 2.0–6.8% are reported as a function of Cu concentration. The highest efficiency of 6.8%, was achieved for solar cell with glass/Mo/CZTGSe/CdS/i-ZnO/ITO structure using the stacking of Cu (3 nm)/Sn (248 nm)/Cu (112 nm)/Zn (174 nm)/Ge (20 nm).     

Nonfullerene Tandem Organic Solar Cells with High Performance of 14.11%

Fabricating solar cells with tandem structure is an efficient way to broaden the photon response range without further increasing the thermalization loss in the system. In this work, a tandem organic solar cell (TOSC) based on highly efficient nonfullerene acceptors (NFAs) with series connection type is demonstrated. To meet the different demands of front and rear sub‐cells, two NFAs named F‐M and NOBDT with a whole absorption range from 300 to 900 nm are designed, when blended with wide bandgap polymer poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBDB‐T) and narrow bandgap polymer PTB7‐Th, respectively, the PBDB‐T: F‐M system exhibits a high V_oc of 0.98 V and the PTB7‐Th: NOBDT system shows a remarkable J_sc of 19.16 mA cm^?2, which demonstrate their potential in the TOSCs. With the guidance of optical simulation, by systematically optimizing the thickness of each layer in the TOSC, an outstanding power conversion efficiency of 14.11%, with a V_oc of 1.71 V, a J_sc of 11.72 mA cm^?2, and a satisfactory fill factor of 0.70 is achieved; this result is one of the top efficiencies reported to date in the field of organic solar cells.     

Synthesis and optimization of P(MMA-BA-MAA)/PEG-based polymer gel electrolytes

A polymer gel electrolyte based on poly(methyl methacrylate-butyl acrylate-methacrylic acid)/polyethylene glycol 400 blend (P(MMA-BA-MAA)/PEG400) was successfully prepared by a simple and efficient procedure. The optimal ionic conductivity was achieved to be 3.12 mS cm^?1 at the temperature of 30 °C when the electrolyte has the composition of 20 wt% P(MMA-BA-MAA)/PEG400 blend, 0.6 M NaI, and 0.06 M I₂ in the solvent γ-butyrolactone (GBL). For tuning the ionic conductivity, various additives were introduced into the polymer gel electrolytes. The measured values of open circuit voltage, short circuit current, and total photovoltaic efficiency indicates that the adding of pyridine (PY) leads to better performance of the final dye-sensitized solar cells (DSSCs), while the adding of Guanidine thiocyante (GuSCN) leads to a worse one. 4-Tert-butylpyridine (TBP) additive takes a more complex effect on the performance of the final DSSCs. For polymer gel electrolyte with 0.5 M pyridine, the final fabricated dye-sensitized solar cell has overall energy conversion efficiency (η) of 3.63 % (0.16 cm² active area) under AM 1.5 at irradiation of 100 mW cm^?2, which reached the level of the liquid electrolyte based device (η = 3.83 % at 0.16 cm² active area). Meanwhile, this gel electrolyte exhibits well long-term stability. The mechanism analysis revealed the dependences of ionic conductivity on the concentration of polymer and NaI and the temperatures.     

Cerium ion redox system in CeO2–xFe2O3 solid solution at high temperatures (1,273–1,673 K) in the two-step water-splitting reaction for solar H2 generation

CeO₂–xFe₂O₃ (x = 0.026–0.214) solid solutions with different Ce:Fe mole ratios (Ce:Fe = 9.5:0.5–7.0:3.0) were prepared as reactive ceramics with the combustion method for solar hydrogen production. The prepared CeO₂–xFe₂O₃ solid solutions were characterized by X-ray diffractometry, ICP atomic emission spectrometry, and Mössbauer spectroscopy. Two-step water-splitting reaction with the CeO₂–xFe₂O₃ solid solution proceeded at 1,673 K for the O₂-releasing reaction and at 1,273 K for the H₂-generation reaction by irradiation of an infrared imaging lamp as a solar simulator. The amounts of H₂ gas evolved in the H₂-generation reaction with CeO₂–xFe₂O₃ solid solutions were 0.97–1.8 cm³/g, the evolved H₂/O₂ ratio was approximately equal to 2 of the stoichiometric value. The amounts of H₂ and O₂ gases were independent of the Ce:Fe mole ratio in the CeO₂–xFe₂O₃ solid solution. It was suggested that the O₂-releasing and H₂-generation reactions with the CeO₂–xFe₂O₃ solid solution were repeated with the reduction and oxidation of Ce⁴⁺–Ce³⁺ enhanced by the presence of Fe³⁺–Fe²⁺.     

Synthesis,characterization, and photovoltaic properties of acceptor–donor–acceptor organic small molecules with different terminal electron-withdrawing groups

Two soluble acceptor–donor–acceptor (A–D–A) type organic small molecules, 2,2′-(5,5′-(1E,1′E)-2,2′-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis(ethene-2,1-diyl)bis(3,4-dihexylthiophene-5,2-diyl))bis(methan-1-yl-1-ylidene)dimalononitrile (BvT-DCN) and 2,2′-(3,3′-(1E,1′E)-2,2′-(5,5′-(1E,1′E)-2,2′-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis(ethene-2,1-diyl)bis(3,4-dihexylthiophene-5,2-diyl))bis(ethene-2,1-diyl)bis(5,5-dimethylcyclohex-2-ene-3-yl-1-ylidene))dimalononitrile (BT-C6), were synthesized by Knoevenagel condensation reaction based on benzothiadiazole, thiophene, and different terminal electron-withdrawing groups. The acceptor group benzothiadiazole and donor group thiophene inside the molecules are connected by all-trans double bonds, which ensures the benzothiadiazole and thiopene groups are in the same plane and makes the molecules have a relative narrow band gap and absorb sunlight in the long wavelength. The terminal electron-withdrawing groups, malononitrile and 2-(5,5-dimethylcyclohex-2-en-1-ylidene)malononitrile (DCM), are symmetrically introduced into the molecules, respectively, to tune the energy level and extend the absorption of the molecules. The UV–Vis absorption spectrum and cyclic voltammetry measurements indicated that BT-C6 has a lower energy band gap (1.60 eV) than BvT-DCN (1.71 eV), which arises from the stronger electron-withdrawing ability of DCM group in BT-C6 than that of malononitrile group in BvT-DCN. And BvT-DCN and BT-C6 have nearly the same highest occupied molecular orbital energy level, ?5.74 eV for BvT-DCN and ?5.72 eV for BT-C6 due to the same electron–donor group of the two compounds. Bulk heterojunction photovoltaic devices were fabricated using BvT-DCN or BT-C6 as donor and (6,6)-phenyl C₆₁-butyric acid methyl ester as acceptor. The device based on BT-C6 has a higher (~8 times) short circuit current and power conversion efficiency than the device based on BvT-DCN, resulting from the wider solar light absorption of BT-C6 and smaller phase separation dimension of the active layer based on BT-C6.     

Giant dielectric, low dielectric loss, and non-ohmic properties of nanocrystalline CaCu3Ti4O12

A simple polymer pyrolysis method has been successfully used to prepare CaCu₃Ti₄O₁₂ (CCTO) nanoparticles by calcination the obtained precursor powder at a low temperature of 800 (CCTO-1) and 850 °C (CCTO-2) in air for 4 h. The XRD results show that both of the calcined powders (CCTO-1 and CCTO-2) are pure having perovskite structure with the crystallite sizes, as evaluated by the XRD line boardening technique, of 47.5 and 75 nm, respectively. The particle sizes as estimated from the bright field images of TEM were found to be in the range of 10–35 and 7–52 nm for CCTO-1 and CCTO-2, respectively. The further sintering of CCTO-1 and CCTO-2 at 1,050 °C in air for 6 h, CCTO-1A and CCTO-2A, are also pure with perovskite structure as indicated by the XRD results. The measurements of the dielectric constant ( $ \varepsilon^{\prime } $ ε ′ ) and the low loss tangent (tanδ) at 1 kHz and 20 °C of CCTO-2A were found to be ~11,472 and ~0.0438, respectively. In addition, the CCTO-2A sample shows a small temperature coefficients ( $ \left| {\Updelta \varepsilon^{\prime } } \right| < 15\,\% $ | Δ ε ′ | < 15 % ) in a wide temperature range from ?50 to 110 °C. The non-Ohmic properties non-linear coefficient (α) of CCTO-1A and CCTO-2A were observed and the non-linear coefficient (α) of them determined in the range of 1–10 mA cm^?2 were found to be 12.00 and 7.26, respectively. Moreover, the breakdown field (E _b ) of CCTO-1A and CCTO-2A ceramics obtained at J = 1 mA cm^?2 were calculated and found to be 811 and 1,342 V cm^?1, respectively.