Poly [2,5-bis(2-decyldodecyl)pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione-(E)-1,2-di(2,2 0 -bithiophen-5-yl) ethene] (PDPPDBTE) was successfully incorporated as a p-type hole transporting material in solid-state organicinorganic hybrid solar cells. The excellent optical and electrical properties of organo-lead halide perovskite (CH 3 NH 3 PbI 3 ) nanocrystals used as light harvesters yielded a 9.2% power conversion efficiency (PCE) for the best-performing cell that exceeded the value (7.6%) obtained from the best hole conductor yet reported (2,2 0 ,7,7 0 -tetrakis(N,N-di-p-methoxyphenyl-amine)9,9 0 -spirobifluorene, spiro-MeOTAD). The high PCE was attributed to the optimal oxidation potential (5.4 eV) and excellent charge carrier mobility of the polymer. The hydrophobicity of the polymer prevented water permeation into the porous perovskite heterojunction, and long-term aging tests over 1000 hours confirmed the enhanced stability of the PDPPDBTE-based cells. Broader contextSolid-state organic-inorganic hybrid solar cells have been extensively investigated as an alternative promising energy conversion devices to the conventional silicon-based photovoltaics. With the successful demonstration of the solar cells which utilize lead halide perovskite nanocrystals as excellent light harvesters the overall efficiencies rapidly increased during the last year, yielding over 15% of remarkable performance. Further enhancement of the efficiency could be realized by developing new hole transporting materials with high electrical properties and proper oxidation potential with respect to the energy level of perovskite. To this end, the conjugated polymers are thought to be an alternative to small molecular hole conductors since they have unique charge transport properties with tunable oxidation potential. In this work, we report an efficient stable hybrid solar cells incorporating diketopyrrolopyrrole-containing polymers (PDPPDBTE). With an appropriate oxidation potential of 5.4 eV vs. the vacuum level, the PDPPDBTE conjugated polymer is expected to function efficiently as a hole transporting material. Furthermore, the excellent long-term stability of polymer-based solar cells also guarantee their potential applications.

Size-tunable mesoporous spherical TiO 2 (MS TiO 2 ) with a surface area of $110 m 2 g À1 have been prepared through combination of ''dilute mixing''-driven hydrolysis of titanium(iv) tetraethoxide and solvothermal treatment. The hierarchically structured MS TiO 2 are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen sorption analysis. Using three different MS TiO 2 (587, 757, and 1554 nm in diameter) as a scattering overlayer on a transparent nanocrystalline TiO 2 film, bi-layered dye-sensitized solar cells (DSCs) have been fabricated. Since the MS TiO 2 particles are comprised of $10 nm nanocrystallites that cluster together to form large secondary spheres, they can function as light scatterers without sacrificing the surface area for dye-uptake. As a result, the present MS TiO 2 -based cells perform a noticeable improvement in the overall efficiency: maximum 9.37% versus 6.80% for the reference cell made of a TiO 2 nanocrystalline film. This extraordinary result is attributed to the dual effects of enhanced dye loading and light scattering.

Stearic acid as a coadsorbent, which has a low dipole moment and high solubility, retarded the rate of dye adsorption during the competitive anchoring process on the TiO(2) layer in dye-sensitized solar cells (DSCs), thereby increasing the content of strongly bound dye on the TiO(2) surface. This resulted in an approximately 25% improvement in both J(SC) and the power conversion efficiency of the DSCs, even for much lower dye coverage.

A series of carbazole-based D-π-A copolymers were synthesized to investigate the influences of conjugation length and structural distortion on intramolecular charge transfer (CT) complexation between the donor (D) and acceptor (A) components. Carbazole presents two possible linkage sites, the 2,7- and 3,6-positions, which led to significant differences in the thermal, photophysical, electrochemical, and electrical properties of the copolymers due to the positioning of the electron-rich nitrogen atom with respect to the copolymer backbone. The copolymers were comprehensively characterized using TGA, DSC, UV−vis, and photoluminescence spectroscopy, cyclic voltammetry, and DFT calculations. P(3,6C-DTBT), which was linked by a thienyl-2′,1′,3′-benzothiadiazole (DTBT) group at the 3,6-positions of the carbazoles so as to directly involve the electron-rich nitrogen atoms in conjugation, exhibited conjugation breaks in the middle of the carbazole units. The breaks resulted in a robust coplanar structure with an extraordinarily low oxidation potential and the ability to stably generate excitons, in contrast with P(2,7C-DTBT), which was linked by DTBT at the 2,7-positions of the carbazole. Two additional hexyl substituents at the 4-position of the thiophene in the DTBT groups of P(2,7C-HDTBT) and P(3,6C-HDTBT), which were identical to P(2,7C-DTBT) and P(3,6C-DTBT), respectively, except for the presence of the substituents, introduced steric hindrance between the D and A units, thereby breaking the coplanarity. Finally, the hole mobilities of the 3,6-carbazole-based copolymers were 1 order of magnitude higher than those of 2,7-carbazole-based copolymers, measured in hole-only devices. This result indicated the presence of stable radical cations and dications at the nitrogen atoms of the copolymers. This work deepens our understanding of carbazole-based D-π-A copolymers and provides insight into the design of novel materials for optoelectronic devices.

We describe the dielectric effects in a novel branched phthalocyanine system. The synthesis and characterization of the hyperbranched structure are provided. The dielectric constant was approximately 45 over many decades of frequency, and the dispersion was small up to 1 MHz. The losses experienced in this novel material were very small (close to 0.001) at high frequency. The mechanism of this novel effect in the branched structure involves a delocalized polaronic state which takes advantage of the strong intramolecular interactions in the system.

Since O'Regan and Grätzel [1] reported the preparation of a lowcost high-efficiency dye-sensitized solar cell (DSC) with 7.9% power conversion efficiency in 1991, [1] tremendous efforts were applied to this field, leading to the achievement of a 10.0% conversion efficiency using the cis-diisothiocyanatob i s ( 2 , 2 ′ -b i p y r i d y l -4 , 4 ′ -d i c a r b o x y l a t o ) r u t h e n i u m ( I I ) bis(tetrabutylammonium) (N719) dye in a liquid junction DSC in 1993. [2] Despite this success, DSCs have several drawbacks that have limited further improvements and widespread adoption of the technology. The dyes are expensive, and exposure to sunlight and high temperatures degrades the device stability. For these reasons, improvements in the stability of the DSC components are an urgent issue in this field. [3] In this regard, several key properties are ideal for devices: (1) low dye loading, (2) high-power conversion efficiency, i.e., simultaneous improvements in the short-circuit current density (J SC ) and open-circuit voltage (V OC ), and (3) long-term stability. To meet criteria 1 and 2, research has focused on identifying dyes with large molar extinction coefficients, [4] but these efforts have met with little success. The coadsorption of dyes with coadsorbents has also been pursued; however, this approach has only succeeded in increasing either J SC (3-phenylpropionic acid as a co-adsorbent) [5] or V OC (tetrabutylammonium chenodeoxycholate, chenodeoxycholic acid as co-adsorbents), [6,7] but not both. Criteria 1 and 2 have been met using a nonvolatile electrolyte rather than a liquid electrolyte, as reported by Grätzel and coworkers. [8] The amphiphilic ruthenium dye was used with hexadecylmalonic acid as a coadsorbent. The long-term stability (criterion 3) of DSCs has recently been achieved through molecular engineering of the sensitizer in conjunction with the use of a robust and nonvolatile electrolyte. [9] However, the conversion efficiency of this DSC was lower than those of conventional DSCs, and the manufacturing costs were higher because of the high costs of the ionic liquid. DSC stability can degrade over time because of several factors, among which may be the evaporation of the liquid electrolyte, irreversible oxidation of the dye, detachment of the dye molecules from the electrode surface in the presence of nucleophiles from water, or decomposition of the liquid electrolytes at high temperatures because of an adsorptive equilibrium process. [3,10] Although many studies have sought to address these issues, remarkably few DSCs possess all three of the desired characteristics, including low cost. Recently, we reported that the coadsorbent stearic acid, which has high solubility in a mixture solution of acetonitrile and t-butanol, leads competitive equilibrium anchoring process, resulting to the reduction of dye aggregation, which improved J SC while reducing the required dye loading. [11] In the line of the extended research, we considered that a surface-induced cross-linking polymerization of a reac...

TiO(2) electrodes, sensitized with the N719 dye at high immersion temperatures during the sensitization process, were found to have large fractions of weakly bound N719 on the electrode surface, which resulted in dye aggregation and decreased device longevity. These disadvantages were ameliorated using a low-temperature stearic acid (SA)-assisted anchoring method described here. The activation energy (ΔE(NS)(++)) and relative fraction of strongly bound N719 were twice as large as the respective values obtained without the use of SA. Slowing of adsorption, both by thermal means and through SA-mediated processes, effectively controlled the binding mode of N719 on the surface of TiO(2). The resulting sensitized electrodes displayed enhanced device longevity and improved generation of photoinduced electrons.

A novel organic hyperbranched copper phthalocyanine was synthesized for use as a hole injection nanolayer on ITO in organic light‐emitting diodes (OLEDs). This material is soluble in organic solvents which allows for processing under anhydrous conditions, unlike water based conventional polymer hole injection layer materials such as poly(3,4‐ethylenedioxythiophene)(PEDOT)/polystyrene sulfonate (PSS). The hyperbranched layer increased the luminous efficiency and brightness of single layer OLED devices, in addition to reducing current leakage which causes crosstalk in panel devices, compared to devices prepared from PEDOT/PSS. Therefore, this material is more suitable for OLED applications due to its processing and performance advantages over conventional commercial conducting polymer compositions.