17 research outputs found
Karriere-Handbuch
We design and synthesize four fused-ring
electron acceptors based on 6,6,12,12-tetrakis(4-hexylphenyl)-
indacenobis(dithieno[3,2-b;2â˛,3â˛-d]thiophene) as the electron-
rich unit and 1,1-dicyanomethylene-3-indanones with 0â
2 fluorine substituents as the electron-deficient units. These
four molecules exhibit broad (550â850 nm) and strong
absorption with high extinction coefficients of (2.1â2.5) Ă 105
Mâ1 cmâ1. Fluorine substitution downshifts the LUMO energy
level, red-shifts the absorption spectrum, and enhances
electron mobility. The polymer solar cells based on the
fluorinated electron acceptors exhibit power conversion
efficiencies as high as 11.5%, much higher than that of their
nonfluorinated counterpart (7.7%). We investigate the effects
of the fluorine atom number and position on electronic
properties, charge transport, film morphology, and photovoltaic properties
Single-Junction Binary-Blend Nonfullerene Polymer Solar Cells with 12.1% Efficiency
A new fluorinated nonfullerene acceptor, ITIC-Th1, has been designed and
synthesized by introducing fluorine (F) atoms onto the end-capping group
1,1-dicyanomethylene-3-indanone (IC). On the one hand, incorporation of
F would improve intramolecular interaction, enhance the pushâpull effect
between the donor unit indacenodithieno[3,2-b]thiophene and the acceptor
unit IC due to electron-withdrawing effect of F, and finally adjust energy levels
and reduce bandgap, which is beneficial to light harvesting and enhancing
short-circuit current density (JSC). On the other hand, incorporation of F
would improve intermolecular interactions through C-F¡¡¡S, C-F¡¡¡H, and
C-FÂˇÂˇÂˇĎ noncovalent interactions and enhance electron mobility, which is
beneficial to enhancing JSC and fill factor. Indeed, the results show that fluorinated
ITIC-Th1 exhibits redshifted absorption, smaller optical bandgap, and
higher electron mobility than the nonfluorinated ITIC-Th. Furthermore, nonfullerene
organic solar cells (OSCs) based on fluorinated ITIC-Th1 electron
acceptor and a wide-bandgap polymer donor FTAZ based on benzodithiophene
and benzotriazole exhibit power conversion efficiency (PCE) as high as
12.1%, significantly higher than that of nonfluorinated ITIC-Th (8.88%). The
PCE of 12.1% is the highest in fullerene and nonfullerene-based single-junction
binary-blend OSCs. Moreover, the OSCs based on FTAZ:ITIC-Th1 show
much better efficiency and better stability than the control devices based on
FTAZ:PC71BM (PCE = 5.22%)
Solution-processed, top-emitting, microcavity polymer light-emitting diodes for the pure red, green, blue and near white emission
Synthesis of Novel Pr-bonded Polymers with Phenanthroline Units for Polymer Memory Devices
Theoretical Studies of the Spin-Dependent Electronic Transport Properties in Ethynyl-Terminated Ferrocene Molecular Junctions
The spin-dependent electron transport in the ferrocene-based molecular junctions, in which the molecules are 1,3-substituted and 1,3â˛-substituted ethynyl ferrocenes, respectively, is studied by the theoretical simulation with nonequilibrium Greenâs function and density functional theory. The calculated results suggest that the substitution position of the terminal ethynyl groups has a great effect on the spin-dependent current-voltage properties and the spin filtering efficiency of the molecular junctions. At the lower bias, high spin filtering efficiency is found in 1,3â˛-substituted ethynyl ferrocene junction, which suggests that the spin filtering efficiency is also dependent on the bias voltage. The different spin-dependent transport properties for the two molecular junctions originate from their different evolutions of spin-up and spin-down energy levels
A rectifying diode with hysteresis effect from an electroactive hybrid of carbazole-functionalized polystyrene with CdTe nanocrystals via electrostatic interaction
One of the strategies to tune current-voltage behaviors in organic diodes is to combine field-induced charge transfer processes with schottky barrier. According to this principle, a rectifying diode with hysteresis effect was fabricated utilizing a hybrid of electroactive polystyrene derivative covalently tethered with electron-donor carbazole moieties and electrostatic linked with electron-acceptor CdTe nanocrystals. Current-voltage characteristics show an electrical switching behavior with some hysteresis is only observed under a negative bias, with three orders of On/Off current ratio. The hybrid material based rectifier exhibits a rectification ratio of six and its maximum rectified output current is about 5 Ă 10â5 A. The asymmetric switching is interpreted as the result of both field induced charge transfer and schottky barrier, capable of reducing the misreading of cross-bar memory. Meanwhile, chemical doping of CdTe nanocrystals instead of physical blend favor their uniform dispersion in matrix and stable operation of device
SingleâJunction BinaryâBlend Nonfullerene Polymer Solar Cells with 12.1% Efficiency
A new fluorinated nonfullerene acceptor, ITIC-Th1, has been designed and synthesized by introducing fluorine (F) atoms onto the end-capping group 1,1-dicyanomethylene-3-indanone (IC). On the one hand, incorporation of F would improve intramolecular interaction, enhance the push-pull effect between the donor unit indacenodithieno[3,2-b] thiophene and the acceptor unit IC due to electron-withdrawing effect of F, and finally adjust energy levels and reduce bandgap, which is beneficial to light harvesting and enhancing short-circuit current density (JSC). On the other hand, incorporation of F would improve intermolecular interactions through C. F center dot center dot center dot S, C. F center dot center dot center dot H, and C. F center dot center dot center dot pi noncovalent interactions and enhance electron mobility, which is beneficial to enhancing JSC and fill factor. Indeed, the results show that fluorinated ITIC-Th1 exhibits redshifted absorption, smaller optical bandgap, and higher electron mobility than the nonfluorinated ITIC-Th. Furthermore, nonfullerene organic solar cells (OSCs) based on fluorinated ITIC-Th1 electron acceptor and a wide-bandgap polymer donor FTAZ based on benzodithiophene and benzotriazole exhibit power conversion efficiency (PCE) as high as 12.1%, significantly higher than that of nonfluorinated ITIC-Th (8.88%). The PCE of 12.1% is the highest in fullerene and nonfullerene-based single-junction binary-blend OSCs. Moreover, the OSCs based on FTAZ: ITIC-Th1 show much better efficiency and better stability than the control devices based on FTAZ: PC71BM (PCE = 5.22%).973 Program [2013CB834702]; National Natural Science Foundation of China [91433114]; Office of Naval Research [N000141410221]; National Science Foundation [DMR-1507249]; Ministry of Science and Technology [2016YFA0200700]; NSFC [21504066, 21534003]; Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy [DE-AC02-05CH11231]SCI(E)ARTICLE182
Effect of the linkage modes of thiolated ethynyl groups on the spin-dependent electronic transport properties in transition metal porphyrin molecular junctions
High Color Rendering Index White-Light Emission from UV-Driven LEDs Based on Single Luminescent Materials: Two-Dimensional Perovskites (C<sub>6</sub>H<sub>5</sub>C<sub>2</sub>H<sub>4</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<i><sub>x</sub></i>Cl<sub>4â<i>x</i></sub>
Two-dimensional
(2D) white-light-emitting hybrid perovskites (WHPs) are promising
active materials for single-component white-light-emitting diodes
(WLEDs) driven by UV. However, the reported WHPs exhibit low quantum
yields (â¤9%) and low color rendering index (CRI) values less
than 85, which does not satisfy the demand of solid-state lighting
applications. In this work, we report a series of mixed-halide 2D
layered WHPs (C<sub>6</sub>H<sub>5</sub>C<sub>2</sub>H<sub>4</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<i><sub>x</sub></i>Cl<sub>4â<i>x</i></sub> (0 < <i>x</i> <
4) obtained from the phenethylammonium cation. Unlike the reported
WHPs including (C<sub>6</sub>H<sub>5</sub>C<sub>2</sub>H<sub>4</sub>NH<sub>3</sub>)<sub>2</sub>PbCl<sub>4</sub>, the mixed-halide perovskites
display morphology-dependent white emission for the different extents
of self-absorption. Additionally, the amount of Br has a huge influence
on the photophysical properties of mixed-halide WHPs. With the increasing
content of Br, the quantum yields of WHPs increase gradually from
0.2 to 16.9%, accompanied by tunable color temperatures ranging from
4000 K (âwarmâ white light) to 7000 K (âcoldâ
white light). When applied to the WLEDs, the mixed-halide perovskite
powders exhibit tunable white electroluminescent emission with very
high CRI of 87â91