A computationally simple yet predictive multi-scale simulation scheme is introduced to estimate zero-field charge mobilities for amorphous OSC materials. A percolating charge model is utilized to ...describe inhomogeneity of hopping trajectories of carriers in amorphous media. The prediction scheme is composed of the following stages: quantum chemical calculation of Marcus inner sphere reorganization energies, molecular dynamics simulations of the amorphous condensed phase bulk structure, automated quantum chemical calculations of the electronic coupling for dimer pairs in the amorphous solid, and calculation of the Marcus theory charge hopping rates and an estimated bulk mobility using the Einstein relation, corrected for the inhomogeneous hopping network of the solid. Comparisons with independent experimental measurements of hole mobility for ten OSC compounds show that this approach gives good correlation between predictions and measurements suitable for ranking systems, and useful quantitative agreement. This low-cost model with minimal complexity is well-suited for incorporation into a virtual materials discovery framework for advanced OSC solutions.
Display omitted
•A method for estimating charge mobility of amorphous molecular solids is proposed.•The model tempers simple diffusion with a correction based on hopping connectivity.•The approach is well suited for initial screening of organic semiconductors.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Temperature can change the charge injection and migration characteristics in the liquid, affecting the insulation performance. First, the influence of temperature on the permittivity and Kerr ...constant of the liquid dielectric is studied. Also, the results prove that the permittivity and Kerr constant of propylene carbonate (PC) decrease with the increase of temperature. Moreover, to explore the influence of temperature on the insulation performance of propylene carbonate, we build a temperature-controllable breakdown test platform under voltage impulse, and the breakdown voltage of PC increases slightly with the increase in temperature. Based on the electrooptic effect, an optical platform is built to measure the electric field under the switching overvoltage. In addition, the space charge distribution is calculated, and the results indicated that the temperature in the range of 10 °C-40 °C is negatively correlated with the net space charge injection. Finally, the temperature effect on the rate of change and mobility of the space charges is explored.
The electrophoretic deposition (EPD) of chitosan on metallic substrates was investigated. The electrophoretic mobility of the natural biopolymer in aqueous solution as a function of pH was studied. ...Because the protonation/deporotonation of chitosan is pH-dependent, the electrophoretic mobility and deposition rate is shown to increase with increasing pH from 2.9 to 4.1. The film growth rate is estimated to vary in the range 0.02–0.08
µm/s depending on the pH value. At high growth rates (>
0.05
µm/s), a porous film is obtained due to hydrogen entrapment. The EPD method developed here is applicable for the surface modification of metal implants by chitosan to develop novel bioactive coatings.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Three new molecular A-π-D-π-A type donors, P1, P2 and P3, comprising an alkylthiothienyl substituted porphyrin electron donor core (D) and two 3-ethylrhodanine electron acceptor moieties (A) ...connected peripherally to the porphyrin core via respectively a monomeric, dimeric or trimeric phenylethynyl π-linkage, are synthesized and studied for their optoelectronic, charge transport, and photovoltaic properties. The hole mobilities of their blend films with PC71BM follow the order of P3> P2 > P1 in hole-only device. When used as electron donors with fullerene acceptor, PC71BM, in conventional bulk heterojunction organic solar cells, the optimal device with P1 donors shows a lower FF, but an intensity stronger and broader EQE, the highest JSC and VOC. As a whole, the PCEs of their optimal devices follow the order of P1> P2 > P3, corresponding to 8.61%, 8.20% and 7.82%, respectively. These results clearly demonstrate the decisive influence of π–linkage length over photovoltaic performance, and that the shorter the π–linkage length the better the photovoltaic performance.
Display omitted
•Three new A-π-D-π-A donors with mono, di and trimeric phenylethynyl π-linkages are synthesized.•The π–linkages influence their optoelectronic, charge transport, and photovoltaic properties.•The donor with trimeric phenylethynyl π-linkages shows the highest hole mobility.•The donor with monomeric phenylethynyl π-linkage performs the best in photovoltaics.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
2,9‐ and 2,10‐diphenylpentacene were synthesized by direct C−H borylation of ketal‐protected pentacene, followed by halodeboronation, resolution of the dihalo isomers, Suzuki arylation, cleavage of ...the ketals and decarbonylation in the solid state. They were studied as main active components in organic field effect transistors (OFETs). Diphenyl substitution of pentacene affects the unit cell dimensions only slightly, preserving a face to edge molecular packing in the first layers of thin films evaporated on SiO2 substrates. Both isomers self‐assemble into nanoribbons during the thin film growth upon vapor deposition. The similarity between the surface induced phases of the 2,9‐isomer and unsubstituted pentacene leads to similar 4‐probe hole mobilities, i. e. 0.13 cm2 V−1 s−1 for the former. Whereas 2,9‐disubstitution thus does essentially preserve the thin film characteristics of unsubstituted pentacene, 2,10‐disubstitution is detrimental to the molecular ordering in the thin films and therefore to the field effect mobility which is only 0.07 cm2 V−1 s−1. The known strong enhancement of field effect mobility observed upon diphenyl substitution of anthracene can thus not be emulated analogously with pentacene.
Exploring morphological structures of new β‐Disubstituted pentacene derivatives: TEM optical micrographs and AFM topographies unveil the impact of chemical structure on 4‐probe field effect hole mobilities.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Metal halide perovskite (MHP) light‐emitting diodes (LEDs) have been widely studied and have been reached to >20% external quantum efficiency, owing to their attractive characteristics (e.g., ...solution processability, tunable bandgap and extremely high color purity, high mobility). During the rapid development of perovskite light‐emitting diodes (PeLEDs), modifying the device architecture has been widely studied as well as improving the crystal quality of MHP to achieve near‐unity photoluminescence quantum yield. However, efforts in device architecture engineering have received less attention despite their significance. Here, strategies are reviewed to enhance the efficiency of PeLEDs in terms of the device engineering by interfacial charge injection/transport, exciton‐quenching blocking, and defect passivation layers for enhancing radiative electron–hole recombination. Strategies are systematically classified for each layer in PeLEDs and discussed the synergetic effect between different strategies. Perspective is also provided on future research on PeLEDs focusing on their architecture.
Perovskite light‐emitting diodes (PeLEDs) are remarkable candidates for the next‐generation display owing to its pure color purity and high efficiency. This review systematically introduces strategies to enhance the efficiencies of PeLEDs in terms of device structural engineering. Hole and electron injection, charge balance, morphology control, defect passivation, and other factors of each interlayer are discussed.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Organic semiconductors with long‐range exciton diffusion length are highly desirable for optoelectronics but currently remain rare. Here, the estimated diffusion length of singlet excitons (LD) in ...2,6‐diphenyl anthracene (DPA) crystals grown by solvent evaporation was shown to be up to approximately 124 nm. These crystals showed a previously unseen parallelogram morphology with layer‐by‐layer edge‐on molecular stacking, isotropic optical waveguiding, radiation rate and non‐radiation rate constants of 0.15 and 0.26 ns−1 respectively, as well as good field‐effect transistor hole mobility and theoretically computed strong electronic couplings as high as 109 meV. Photoresponse experiments revealed that the photoconductivity of DPA crystals is surprisingly not related to the radiative pathway but associated with rapid exciton diffusion to the crystal surface for charge separation and carrier bimolecular recombination. Taken together, DPA was shown to be a promising semiconducting material for a new organic optoelectronics paradigm.
Crystal matter: The estimated singlet exciton diffusion length is 124 nm in 2,6‐diphenyl anthracene crystals for advanced optoelectronics. The crystals show parallelogram morphology, a non‐radiation rate constant of 0.26 ns‐1, good field‐effect transistor hole mobility, and strong electronic couplings. These advantages allow excitons to rapidly diffuse to the crystal surface for charge separation and bimolecular recombination in photoconductivity experiments.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Display omitted
•A novel push-pull semiconductor, namely ENBT was designed and synthesized.•The mobility properties of ENBT film were evaluated.•The morphology property of ENBT films were ...investigated by AFM.
A novel push-pull oligomeric semiconductor, ENBT based on naphthodithiophene-benzothiodiazole was successfully designed and synthesized. ENBT was fully characterized by 1H NMR, MS, thermogravimetric analysis (TGA), UV–vis spectra, and cyclic voltammetry (CV). Furthermore, ENBT-based OFETs were fabricated by solution-processed dip-coating technique and its charge transporting property was investigated. The film of ENBT exhibited a hole mobility as high as 1.4 × 10−2 cm2/(Vs) with a current on/off ratio of 106–107 after annealed at 160 °C. In order to give an insight to the transporting property of ENBT films, thin film morphologies after annealing at different temperatures were also studied by atomic force microscopy (AFM).
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Excited state dynamics and charge transfer property of an orange-red thermally activated delayed fluorescence (TADF) emitter are theoretically investigated by a quantum mechanics/molecular mechanics ...(QM/MM) method and kinetic Monte Carlo simulation. The factors that influence internal quantum efficiency of the organic light-emitting diode (OLED) based on an asymmetric donor–acceptor (D–A) type molecule 10-(7-fluoro-2,3-diphenylquinoxalin-6-yl)-10H-phenoxazine (FDQPXZ) are analyzed. The results show that the intramolecular rotation of donor unit is restricted because of the enhanced intermolecular interaction in solid phase, which hinders the non-radiative consumption of the excited state energy. The decreased reorganization energy in solid phase is mainly contributed by dihedral angle in low-frequency (<500 cm−1) region. Moreover, the non-radiative decay rate from the first singlet excited state (S1) to the ground state (S0) in solid phase is shown to be smaller than that in gas phase. In order to explore the charge transfer process in the film of FDQPXZ, Marcus theory is used to study the hole and electron transfer rates, and the charge mobility is thus obtained by Monte Carlo simulation. The theoretical calculation indicates that the FDQPXZ film is a p-type organic molecular material under the hopping mechanism. Intermolecular interaction for theoretical simulation of the working principle of OLEDs is highlighted.
Investigation about the excited state dynamics of TADF emitter through a combined quantum mechanics/molecular mechanics (QM/MM) method. Display omitted
•Excited state dynamics of a TADF emitter is theoretically investigated by QM/MM method.•Hole and electron transfer rates are studied by Marcus theory.•Charge mobility is obtained by Monte Carlo simulation.•Factors that influence internal quantum efficiency of TADF-OLEDs are analyzed.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
High performance of panchromatic organic photodetectors (OPDs) with a wide spectral response ranged from 300 to 1000 nm were realized through adding 6,6-phenyl-C71-butyric acid methylester (PC71BM) ...fullerene as an electron acceptor into the polymer donor of poly (3-hexylthiophene) (P3HT) and the small molecular non-fullerene acceptor of 2, 2′-((2Z,2′Z)-(((4, 4, 9, 9-tetrakis(4-hexylphenyl)-4, 9-dihydro-sindaceno1, 2-b:5, 6-b′dithiophene-2, 7-diyl)bis(4-((2-ethylhexyl)oxy)thiophene-5, 2-diyl))bis-(methanylylidene))bis(5, 6-difluoro-3-oxo-2, 3-dihydro-1H-indene-2, 1-diylidene))dimalononitrile (IEICO-4F) host system. The fabricated OPD exhibited a high detectivity (D*) of 1.35 × 1012 Jones at 805 nm by adding 10 wt% PC71BM, which is 1.5 folds higher than it from the control system. The improved performance was mainly attributed to the increased light absorption in the short wavelength range and cascade energy level alignment, which is responsible for the efficient light harvesting and exciton utilization. Furthermore, the active layer morphology was optimized by adjusting the ratio of PC71BM acceptor, which efficiently enhances charge transport and mobility of the device as well as suppress bimolecular recombination. This work indicates that adding fullerene into non-fullerene system plays a positive effect on the device performance of panchromatic OPDs.
Display omitted
•High photodetectivity with the increase of Jph and the decrease of Jdark is achieved.•Optical and electrical properties of panchromatic OPDs are detailed studied.•Charge transfer and mobility of OPDs are enhanced by adding fullerene acceptors.•Morphology control effects of PC71BM on device performance have been disclosed.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
