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Solar cells made of lead perovskite crystals have attracted much attention for their high performance, but far less attention as a subject of crystal engineering. Here, we report that citric acid (CA) and chloride anion, working together, modulate crystal growth of CH3NH3PbI3, producing sub-mm-sized cuboid crystalsa morphology more suitable for close packing in a thin film than the commonly observed elongated dodecahedral morphology. By using a 15 wt % CA-doped precursor solution, we formed a single layer of large, flat, and oriented cuboid crystals with minimum crystal domain boundaries and maximum contact with neighboring layers, and fabricated an archetypal inverted-structured device of 4 mm2 area, which showed, reproducibly and with little hysteresis, 16.75% power conversion efficiency (PCE), 26% higher than the PCE obtained for a polycrystalline film made without CA doping. Under weaker irradiation of a 1 cm2 device, the PCE improved from 14.52% (one sun) to 20.4% (0.087 suns). Under illumination with white light emitting diode, a 10 wt % CA-doped device showed PCE of 28.1%, suggesting an advantage of PVK-SCs for indoor applications. Further studies on crystal growth modulation will be beneficial for manufacturing efficient and stable lead perovskite solar cells. [ABSTRACT FROM AUTHOR]

We report the synthesis of two noveldonor–acceptor copolymerspoly{[N, N′-bis(alkyl)-1,4,5,8-naphthalenediimide-2,6-diyl-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-2-(2-(thiophen-2-yl)vinyl)thiophene]} (PNVTs) based onnaphthalenediimide (NDI) acceptor and (E)-2-(2-(thiophen-2-yl)vinyl)thiophenedonor. The incorporations of vinyl linkages into polymer backbonesmaintain the energy levels of the lowest unoccupied molecular orbitsat −3.90 eV, therefore facilitating the electron injection.Moreover, the energy levels of the highest occupied molecular orbitsincrease from −5.82 to −5.61 eV, successfully decreasingthe hole injection barrier. Atomic force microscopy measurements indicatethat PNVTs thin films exhibit larger polycrystalline grains comparedwith that of poly{[N, N′-bis(2-octyldodecyl)-1,4,5,8-naphthalenediimide-2,6-diyl]-alt- 5,5′-(2,2′-bithiophene)}[P(NDI2OD-T2)], consistent with the stronger π–πstacking measured by grazing incidenceX-ray scatting. To optimize devices performance, field-effect transistors(FETs) with three devices configurations have been investigated. Theresults indicate that the electron mobility of the vinyl-containingPNVTs exhibit about 3–5 times higher than that of P(NDI2OD-T2).Additionally, the vinyl-linkages in PNVTs remarkably enhance ambipolartransport of their top-gate FETs, obtaining high hole and electronmobilities of 0.30 and 1.57 cm2V–1s–1, respectively, which are among the highest valuesreported to date for the NDI-based polymers. Most importantly, ambipolarinverters have been realized in ambient, exhibiting a high gain of155. These results provide important progresses in solution-processedambipolar polymeric FETs and complementary-like inverters. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis and characterizationoftwo new D-A-D molecules (E)-5,5′-bis(5-(benzo[b]thiophen-2-yl)thiophen-2-yl)-1,1′-bis(2-ethyl-hexyl)-[3,3′-bipyrrolylidene]-2,2′(1H,1′H)-dione (BTBPD) and (E)-5,5′-bis- (5-(benzo[b]furan-2-yl)thiophen-2-yl)-1,1′-bis(2-ethylhexyl)-[3,3′-bipyrrolylidene]-2,2′(1H,1′H)-dione (BFBPD). They entail bipyrrolylidene-2,2′(1H,1′H)-dione (BPD, known as Pechmann dye) as theelectron-accepting core that is flanked by two benzo[b]thiophene moieties and two benzo[b]furan moieties,respectively. Crystal structures of BTBPDand BFBPDprovide solid evidence for the intermolecular donor–acceptor(D-A) interactions, which are favorable for improving charge transportperformance. Organic field-effect transistors (OFETs) were preparedbased on thin films of BTBPDand BFBPDthroughsolution-processed technique. OFETs of BTBPDexhibitrelatively high hole mobility up to 1.4 cm2V–1s–1with high on/off ratio up to 106. In comparison, the hole mobility of OFETs with BFBPD(0.14 cm2V–1s–1) is relatively low, because of the poor thin-film morphology andlow molecular ordering, even after annealing. Thin-film morphologicaland XRD studies were carried out to understand the variation of holemobilities after annealing at different temperatures. The presentstudies clearly demonstrate the potentials of BPDthatis planar and polar as the electron-acceptor moiety to build D-A moleculesfor organic semiconductors with good performance. [ABSTRACT FROM AUTHOR]

Because of its atomic thickness, excellent properties, and widespread applications, graphene is regarded as one of the most promising candidate materials for nanoelectronics. The wider use of graphene will require processes that produce this material in a controllable manner. In this Account, we focus on our recent studies of the controllable chemical vapor deposition (CVD) growth of graphene, especially few-layer graphene (FLG), and the applications of this material in electronic devices. [ABSTRACT FROM AUTHOR]

We demonstrated a polymeric thin film fabrication process in which molecular-scale crystallization proceeds with additive film growth, by employing an innovative vapor-assisted deposition process termed matrix-assisted pulsed laser evaporation (MAPLE). In comparison to solution-casting commonly adopted for the deposition of polymer thin films, this physical vapor deposition (PVD) methodology can prolong the time scale of film formation and allow for the manipulation of temperature during deposition. For the deposition of molecular and atomic systems, such a PVD manner has been demonstrated to facilitate molecular ordering and delicately manipulate crystalline morphology during film growth. Here, using MAPLE, we deposited thin films of a model polymer, poly(ethylene oxide) (PEO), atop a temperature-controlled substrate with an average growth rate of less than 10 nm/h. The mechanism of deposition is sequential addition of nanoscale liquid droplets. We discovered that the deposition process leads to the formation of two-dimensional (2D) PEO crystals, composed of monolamellar crystals laterally grown from larger nucleus droplets. The 2D crystalline coverage and crystal thickness of the films can be manipulated with two processing parameters, deposition time, and temperature. [ABSTRACT FROM AUTHOR]

A new diketopyrrolopyrrole-based π-conjugated copolymer(PDPP5T)with high molecular weight has been synthesized by Stille couplingpolymerization of 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-octyldodecyl)pyrrolo-[3,4-c]pyrrole-1,4(2H,5H)-dionewith α,α′-bis(trimethylstannyl)-terthiophene. Itshole mobility without thermal annealing reaches 1.08 cm2V–1s–1, and a higher hole mobilityof 3.46 cm2V–1s–1is obtained annealed at 200 °C directly in an air atmosphere.This indicates that introducing a longer β-unsubstituted quinquethiophene(5T) unit into the main-chain of DPP-oligothiophene copolymer producesmuch pronounced p-type behavior and also reduces the steric hindranceof the bulk side-chain groups, which is favorable to enhance the molecularordering capability at low temperatures and improve the organic thin-filmtransistors (OTFT) performances. This work demonstrates that PDPP5Tis a promising material that can be applied to the cost-effectiveand large-scale production of OTFTs. [ABSTRACT FROM AUTHOR]

Two structural isomers of six-fused-ring sulfur-containing molecules were synthesized as active materials for p-type organic field-effect transistors, and their optical and electrochemical properties were characterized. Field-effect transistors based on these compounds were fabricated to investigate the relationships between structures and semiconductor properties. [ABSTRACT FROM AUTHOR]