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A new series of triphenylamine (TPA)‐functionalized isomeric polythiophenes are developed as hole transporting materials (HTM) for inverted tin‐based perovskite solar cells (TPSCs). Bithiophene (BT) is first functionalized with two TPA (electron donor; D) at 3 and 5 positions to give two structural isomeric compounds (3BT2D and 5BT2D). The functionalized BT2Ds are then coupled with 3,3′‐bis(tetradecylthio)‐2,2′‐bithiophene (SBT‐14)/3,3′‐ditetradecyl‐2,2′‐bithiophene (BT‐14) to produce structural isomeric polythiophenes (1‐4), which are compared to conventional poly[N,N″‐bis(4‐butylphenyl)‐N,N″‐bis(phenyl)‐benzidine] (poly‐TPD) as HTMs for TPSCs. With the appropriate alignment of energy levels with regard to the perovskite layer, the TPA‐functionalized polymers‐based TPSCs exhibit enhanced operational stability and efficiency. Moreover, the long thiotetradecyl chain in SBT‐14 with intramolecular S(alkyl)∙∙∙S(thio) interactions restricts the molecular rotation and has a strong impact on the molecular solubility and wettability of the film during device fabrication. Among all the polymers studied, TPSCs fabricated with 3‐SBT‐BT2D polymer exhibit the highest hole mobility as well as the slowest charge recombination and achieve the highest power conversion efficiency of 8.6%, with great long‐term stability for the performance retaining ≈90% of its initial values for shelf storage over 4000 h, which is the best efficiency for non‐PEDOT:PSS‐based TPSCs ever reported. [ABSTRACT FROM AUTHOR]

The defects at the interface and grain boundaries of perovskite films downgrade the performance of perovskite solar cells (PSCs) dramatically. Hence, improving perovskite film quality is essential for the achievement of high-performance solar cells. Herein, three new dicyclopentadithienothiophene (DCDTT)-based non-fullerene acceptors (NFAs) IN-DCDTT (1), INCl-DCDTT (2), and INBr-DCDTT (3) are developed as a promising platform for organic–inorganic hybrid perovskite solar cells to achieve simple preparation, high efficiency, and good stability. SEM and XRD data indicate that, with the addition of chlorinated NFA 2 in the active layer preparation, perovskite hybrid films exhibit larger grain sizes and higher crystallinity than pristine perovskite films. As shown by EDS and IR, all the non-fullerene acceptors (compounds 1–3) with functional carbonyl (C＝O) and cyano (C≡N) groups have good interaction with undercoordinated Pb atoms and passivate the trap states in the perovskite films. Time-resolved photoluminescence reveals that the molecule INCl-DCDTT (2) facilitates efficient hole extraction. Consequently, solar cells based on 2−perovskite hybrid films yield an excellent power conversion efficiency of 21.39% with an FF of 0.82, a Jsc of 23.71 mA cm−2, and a Voc of 1.10 V, which represents a significant improvement as compared to a PCE of 17% obtained for the control device. Meanwhile, devices based on IN-DCDTT (1) and INBr-DCDTT (3)−perovskite hybrid films also show enhanced performance with a slightly lower PCE of 19.21% and 20.59%, respectively than cells based on 2−perovskite hybrid films. The cost-effective chlorinated INCl-DCDTT (2) and brominated INBr-DCDTT (3) organic small molecules were successfully used as donor passivation agents to improve the photovoltaic performance of Pb-based PSCs. Furthermore, compound 1–3 derived PSC devices also exhibit excellent long-term stability enhancement. In particular, a device based on INCl-DCDTT (2) treated perovskite retains ∼90% of the initial PCE after 63 days in a glove box as compared to that (55%) of the control device. This simple surface treatment, by the addition of new NFAs, provides a new strategy to simultaneously passivate surface defects and enhance charge transport at the device interface. [ABSTRACT FROM AUTHOR]

Two solution‐processable organic semiconductors, DFPT‐DTTR (1) and DFPbT‐DTTR (2), composed of pentafluorophenyl (FP) end‐capped 3,5‐dialkyl dithienothiophene (DTTR) core with thiophene (T) or bithiophene (bT) as π‐bridged spacers are developed and investigated for their optical, electrochemical, microstructural, and electrical properties. With more conjugated bithiophene units, compound 2 exhibits a red‐shifted UV–vis absorption band and upshifted HOMO/downshifted LUMO energy levels. According to the density functional theory, compound 2 features a more twisted molecular structure due to the intrinsic non‐coplanar blocks in the π‐backbones. Compound 1‐based organic field effect transistors exhibit efficient hole transport with mobility up to 0.48 cm2 V−1 s−1. This is one of the high mobility organic semiconductors exhibiting p‐channel characteristics based on solution‐processable small molecular FP end‐capped fused/oligothiophenes. With large and interconnected crystalline morphologies, decreased π–π stacking distance, and less steric hindrance, compound 1 exhibits two orders of magnitude higher mobility than the more distorted 2, which exhibits lower hole mobility of 1.82 × 10−3 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

Three new solution‐processable organic semiconductors (1–3) are synthesized and characterized for p‐type organic field effect transistors (OFETs). The backbone of these small molecules is modified by expanding the central core conjugation from thienothiophene (TT) to dithienothiophene (DTT) and tetrathienoacene (TTA), which are end‐capped with soluble β‐substituted alkyl chains dithienothiophenes (DTTR) to generate DTTR‐TT (1), DTTR‐DTT (2), and DTTR‐TTA (3). The highest mobility of 0.016 cm2 V−1 s−1 is achieved using solution‐sheared DTTR‐TTA film due to the extended conjugated TTA core, which enhances the intermolecular interaction and generates an efficient percolation for the OFET channel. Solution blending of crystalline DTTR‐TT small molecules with oriented‐packing polymer dithienothiophene‐thioalkylbithiophene (PDTT‐SBT) polymer leads to significantly enhanced mobilities from 0.0009 up to 0.22 cm2 V−1 s−1, occurring at an optimized 30% DTTR‐TT composition in the blend. Hole mobility of 30% DTTR‐TT blend is 0.22 cm2 V−1 s−1 which is higher than pristine small molecule DTTR‐TT (0.0009 cm2 V−1 s−1) and polymer PDTT‐SBT (0.067 cm2 V−1 s−1), respectively. An efficient strategy to enhance the mobility of small molecule DTTR‐TT by blending with easily synthesizable PDTT‐SBT polymer is reported. [ABSTRACT FROM AUTHOR]

Two tetrathioalkyl-substituted bithiophene-based small molecule quinoids (TSBTQs) having different chain lengths (thio-hexyl and -decyl) are synthesized and applied as an n-type active component in organic field effect transistors (OFETs). The resulting two TSBTQs exhibit good solubility in various organic solvents and LUMO levels below −4.0 eV. The theoretical DFT calculation supported by single crystal structures confirms the π-conjugated backbone planarity due to the S(thiophene)⋯S(alkyl) non-covalent interaction. Optimized TSBQT-10 OFETs exhibit an electron mobility of 0.18 cm2 V−1 s−1, which is higher than that of TSBTQ-6 (0.09 cm2 V−1 s−1). The reliability of the OFETs under representative environmental and operational conditions is also determined. The effects of side chains including their lengths and contribution to the main chain π-system coplanarity presented here demonstrate an efficient method to manipulate the charge carrier mobility of the quinoidal organic semiconductors. [ABSTRACT FROM AUTHOR]

Presents a study that examined the electrochemical etching process of an n-Si(111) electrode in dilute NH[sub 4]F solutions under potential control by employing in situ scanning tunneling microscopy. Details of the experiment; Results; Discussion.

Three new organic semiconductors with alkyl chain-substituted tetrathienoacene (TTAR) as the central core and both ends capped with thiophene (DT-TTAR), thienothiophene (DTT-TTAR) and dithienothiophene (DDTT-TTAR) have been synthesized and characterized for organic field effect transistor (OFET) applications. A hole mobility of 0.81 cm2 V−1 s−1 was achieved for the DDTT-TTAR film, which represents the highest mobility yet found for a solution-processable p-type TTAR-based small molecular semiconductors. [ABSTRACT FROM AUTHOR]

Three new donor-π-donor (D-π-D) tetrathienoacene (thieno[2′,3′:4,5]thieno[3,2- b]thieno[2,3- d]thiophene (TTA))-cored chromophores, end-functionalized with electron-donating triphenylamine (TPA) groups, were developed and characterized for their two-photon-related properties by using both nano- and femtosecond laser pulses as the probing tools. TTA-based chromophores exhibit stronger and more widely dispersed two-photon absorption (2PA) than those of dithienothiophene (DTT)-based congeners. As a consequence, the bithiophene-conjugated TTA chromophore exhibits the highest maximum 2PA cross-section value (up to 2500 GM) with good thermal stability, and thus, it is the best performing two-photon chromophore among the studied model compounds. The bithiophene-conjugated DTT analogue exhibits the second highest maximum two-photon absorptivity of 1950 GM, which is nearly 7 times larger than that of previously reported DTT-based chromophores. [ABSTRACT FROM AUTHOR]

New asymmetric phenyl and perfluorophenyl end-functionalized dithienothiophene (DTT)- and bisdithienothiophene (BDTT)-based fused-thiophene derivatives (FPP-DTT; 1 and FPP-BDTT; 3) were synthesized and characterized for organic thin-film transistor (OTFT) applications. For comparison, symmetric phenyl end-capped dithienothiophene and bisdithienothiophene derivatives DP-DTT (2) and DP-BDTT (4) were also explored in parallel. The crystal structures of all four molecules were determined via single-crystal X-ray diffraction. Asymmetric compounds 1 and 3 exhibit face-to-face π–π stacking, while symmetric 2 and 4 show herringbone stacking. Single-crystal and thin-film transistors based on these four materials were fabricated. For single-crystal transistors, asymmetric FPP-DTT and FPP-BDTT gave high p-channel mobilities of 0.74 and 0.73 cm2 V−1 s−1, respectively, as well as current on/off ratios of ∼105. Symmetric DP-DTT and DP-BDTT gave relatively lower p-channel mobilities of 0.36 and 0.41 cm2 V−1 s−1, respectively. For thin-film transistors, FPP-DTT and DP-DTT films deposited at 25 °C exhibited decent p-channel characteristics with a carrier mobility as high as 0.15 and 0.20 cm2 V−1 s−1, respectively for top-contact/bottom-gate OTFT devices. The device characteristics on various gate dielectrics have been correlated with the film morphologies and microstructures of the corresponding compounds. [ABSTRACT FROM AUTHOR]

A novel reaction route for the oxidation of thiol groups to disulfide bonds in mesoporous silicas with the aid of Cu2+adsorption is reported for the first time, and most importantly it can serve as a diagnostic reaction for probing the spatial proximity and distribution of organic functional groups. [ABSTRACT FROM AUTHOR]

Electrochemical scanning tunneling microscopy (ECSTM) has been used to examine the adlayer of octa-alkoxy-substituted copper(II) phthalocyanines (CuPc(OC8H17)8) on Au(111) in 0.1 M HClO4, where the molecular adlayer was prepared by spontaneous adsorption from a benzene solution containing this molecule. Topography STM scans revealed long-range ordered, interweaved arrays of CuPc(OC8H17)8 with coexistent rectangular and hexagonal symmetries. High-quality STM molecular resolution yielded the internal molecular structure and the orientation of CuPc(OC8H17)8 admolecules. These STM results could shed insight into the method of generating ordered molecular assemblies of phthalocyanine molecules with long-chained substitutes on metal surface. Microsc. Res. Tech., 2008. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

In situ scanning tunneling microscopy (STM) was used to examine the structure of thiocyanate adlayers specifically adsorbed on Rh(111) in solutions of potassium hydroxide and perchloric acid, both containing potassium thiocyanate (KSCN). An atomically flat terrace-step structure was consistently observed on Rh(111) surfaces prepared by the flame-annealing-quenching method. The Rh(111)-(1 × 1) atomic structure was discerned on the atomically flat terrace even in the alkaline solution. High-resolution STM images disclosed two different structures of the SCN− adlayers, ( ) and (2 × 2), in the alkaline and the acidic media, respectively. In each structure, an individual adsorbed SCN− ion appeared as a single spot with a constant corrugation height in STM images, suggesting that SCN− ions adsorbed predominantly with their S-ends at particular bonding sites on Rh(111). The difference in the adlayer structure in the two solutions can be attributed to the interaction between adsorbed SCN− and coadsorbed K+ in the alkaline solution, and is different from that between adsorbed SCN− and H+ in the acidic solution. [ABSTRACT FROM AUTHOR]

Developing efficient interfacial hole transporting materials (HTMs) is crucial for achieving high‐performance Pb‐free Sn‐based halide perovskite solar cells (PSCs). Here, a new series of benzodithiophene (BDT)‐based organic small molecules containing tetra‐ and di‐triphenyl amine donors prepared via a straightforward and scalable synthetic route is reported. The thermal, optical, and electrochemical properties of two BDT‐based molecules are shown to be structurally and energetically suitable to serve as HTMs for Sn‐based PSCs. It is reported here that ethylenediammonium/formamidinium tin iodide solar cells using BDT‐based HTMs deliver a champion power conversion efficiency up to 7.59%, outperforming analogous reference solar cells using traditional and expensive HTMs. Thus, these BDT‐based molecules are promising candidates as HTMs for the fabrication of high‐performance Sn‐based PSCs. [ABSTRACT FROM AUTHOR]

A combination of a solution process and the control of the electric potential for magnetism represents a new approach to operating spintronic devices with a highly controlled efficiency and lower power consumption with reduced production cost. As a paradigmatic example, we investigated Co/Pt(111) in the Bloch-wall regime. The depression in coercive force was detected by applying a negative electric potential in an electrolytic solution. The reversible control of coercive force by varying the electric potential within few hundred millivolts is demonstrated. By changing the electric potential in ferromagnetic layers with smaller thicknesses, the efficiency for controlling the tunable coercive force becomes higher. Assuming that the pinning domains are independent of the applied electric potential, an electric potential tuning-magnetic anisotropy energy model was derived and provided insights into our knowledge of the relation between the electric potential tuning coercive force and the thickness of the ferromagnetic layer. Based on the fact that the coercive force can be tuned by changing the electric potential using a solution process, we developed a novel concept of electric-potential-tuned magnetic recording, resulting in a stable recording media with a high degree of writing ability. [ABSTRACT FROM AUTHOR]