We estimate the hole mobility for oligoacene crystals using quantum mechanics (QM) to calculate the reorganization energy and electron-transfer coupling matrix elements and molecular dynamics (MD) to do the thermal averaging. Using an incoherent transport model we calculate a hole mobility of 6.5 cm 2 /(V s) for pentacene crystals at 300 K. This can be compared to recent experimental results of 5 cm 2 /(V s). However, we find that an alternative packing into the crystal could lead to a hole mobility of 15.2 cm 2 /(V s). This suggests that current materials might still be improved by a factor of ∼3. Such calculations might be useful for finding solid-state structures that would increase the hole mobility for use in high-performance molecular devices.

Lead-based perovskite nanocrystals (NCs) have outstanding optical properties and cheap synthesis conferring them a tremendous potential in the field of optoelectronic devices. However, two critical problems are still unresolved and hindering their commercial applications: one is the fact of being lead-based and the other is the poor stability. Lead-free all-inorganic perovskite Cs Bi X (X=Cl, Br, I) NCs are synthesized with emission wavelength ranging from 400 to 560 nm synthesized by a facile room temperature reaction. The ligand-free Cs Bi Br NCs exhibit blue emission with photoluminescence quantum efficiency (PLQE) about 0.2 %. The PLQE can be increased to 4.5 % when extra surfactant (oleic acid) is added during the synthesis processes. This improvement stems from passivation of the fast trapping process (2-20 ps). Notably, the trap states can also be passivated under humid conditions, and the NCs exhibited high stability towards air exposure exceeding 30 days.

Lead-free double-perovskite nanocrystals (NCs), that is, Cs2AgIn x Bi1–x Cl6 (x = 0, 0.25, 0.5, 0.75, and 0.9), that can be tuned from indirect band gap (x = 0, 0.25, and 0.5) to direct band gap (x = 0.75 and 0.9) are designed. Direct band gap NCs exhibit 3 times greater absorption cross section, lower sub-band gap trap states, and >5 times photoluminescence quantum efficiency (PLQE) compared to those observed for indirect band gap NCs (Cs2AgBiCl6). A PLQE of 36.6% for direct band gap NCs is comparable to those observed for lead perovskite NCs in the violet region. Besides the band edge violet emission, the direct band gap NCs exhibit bright orange (570 nm) emission. Density functional theory calculations suggesting forbidden transition is responsible for the orange emission, which is supported by time-resolved PL and PL excitation spectra. The successful design of lead-free direct band gap perovskite NCs with superior optical properties opens the door for high-performance lead-free perovskite optoelectronic devices.

Conjugated microporous polymers are a new class of porous materials with an extended π-conjugation in an amorphous organic framework. Owing to the wide-ranging flexibility in the choice and design of components and the available control of pore parameters, these polymers can be tailored for use in various applications, such as gas storage, electronics and catalysis. Here we report a class of cobalt/aluminium-coordinated conjugated microporous polymers that exhibit outstanding CO2 capture and conversion performance at atmospheric pressure and room temperature. These polymers can store CO2 with adsorption capacities comparable to metal-organic frameworks. The cobalt-coordinated conjugated microporous polymers can also simultaneously function as heterogeneous catalysts for the reaction of CO2 and propylene oxide at atmospheric pressure and room temperature, wherein the polymers demonstrate better efficiency than a homogeneous salen-cobalt catalyst. By combining the functions of gas storage and catalysts, this strategy provides a direction for cost-effective CO2 reduction processes.

Overall system energyEquation (1) Below follows a description of the partial energies introduced in equation (1). Bond Order and Bond EnergyA fundamental assumption of ReaxFF is that the bond order BO' ij between a pair of atoms can be obtained directly from the interatomic distance r ij as given in Equation (2). In calculating the bond orders, ReaxFF distinguishes between contributions from sigma bonds, pi-bonds and double pi bonds.

Lead-free perovskite nanocrystals (NCs) were obtained mainly by substituting a Pb cation with a divalent cation or substituting three Pb cations with two trivalent cations. The substitution of two Pb cations with one monovalent Ag and one trivalent Bi cations was used to synthesize Cs AgBiX (X=Cl, Br, I) double perovskite NCs. Using femtosecond transient absorption spectroscopy, the charge carrier relaxation mechanism was elucidated in the double perovskite NCs. The Cs AgBiBr NCs exhibit ultrafast hot-carrier cooling (<1 ps), which competes with the carrier trapping processes (mainly originate from the surface defects). Notably, the photoluminescence can be increased by 100 times with surfactant (oleic acid) added to passivate the defects in Cs AgBiCl NCs. These results suggest that the double perovskite NCs could be potential materials for optoelectronic applications by better controlling the surface defects.

The formulation min x,y f (x) + g(y) subject to Ax + By = b, where f and g are extended-value convex functions, arises in many application areas such as signal processing, imaging and image processing, statistics, and machine learning either naturally or after variable splitting. In many common problems, one of the two objective functions is strictly convex and has Lipschitz continuous gradient. On this kind of problem, a very effective approach is the alternating direction method of multipliers (ADM or ADMM), which solves a sequence of f /g-decoupled subproblems. However, its effectiveness has not been matched by a provably fast rate of convergence; only sublinear rates such as O(1/k) and O(1/k 2) were recently established in the literature, though these rates do not require strict convexity. This paper shows that global linear convergence can be guaranteed under the above assumptions on strict convexity and Lipschitz gradient on one of the two functions, along with certain rank assumptions on A and B. The result applies to the generalized ADM that allows the subproblems to be solved faster and less exactly in certain manners. The derived rate of convergence also provides some theoretical guidance for optimizing the ADM parameters. In addition, this paper makes meaningful extensions to the existing global convergence theory of the generalized ADM.

Documentary statementFigure S1 Illustrations of the identical surrounding of random selected molecules in the rubrene crystals.The derivation of eq. 8 Table S1 Computation details of internal reorganization energy (λ). E(neutral in neutral geometry), E*(neutral in ion geometry), E + (ion in ion geometry) and E + * (ion in neutral geometry) are in Hartree, and the VIP(vertical ionization potential) and λ are in eV.