There are a few reports that the optoelectronic properties of the methoxyaniline-based hole-transporting materials are intimately correlated with the positions of −OMe substituents. To dig into this phenomenon deeply, we theoretically design five new hole-transporting materials (HTMs) based on 2′,7′-bis(bis(4-methoxyphenyl)amino)spiro[cyclopenta[2,1-b:3,4-b′]dithiophene-4,9′-fluorene] (FDT) through altering the positions of −OMe substituents. Then, the electronic structures, optical properties, and hole-transporting properties are investigated at the molecular level via density functional theory and Marcus theory coupled to Einstein relation. The calculated results reveal that the derivatives with o-OMe or m-OMe substituent exhibit lower HOMO levels, favoring higher open-circuit voltages. Most importantly, benefitting from greater order and compact intermolecular stacking, the derivatives with o-OMe substituents (F1, F3) as HTMs exhibit relatively decent hole mobilities (F1: 6.29 × 10–2 cm2 V–1 s–1; F3: 2.49 × 10–3 cm2 V–1 s–1), which are two or three orders of magnitude higher than that of FDT. Quantum chemistry calculation and crystal packing arrangement simulation indicate that −OMe substituents at different positions show disparate orientations and thus affect the molecular stacking. Our work reiterates the importance of molecular configuration for the materials properties and provides those who are engaged in upgrading the performances of hole-transporting materials a new train of thought and tactics with ease and economy.
ABSTRACT:A novel 2D representation (M-curve) has been provided to visualize the structure information of protein secondary structure sequences: (1) end point of the curve reflects difference of amino acid residue numbers in ␣-helices and -strands of a protein; (2) Up/down ladder-like structures in the curve show that ␣-helices/-strands appear sequentially in this region; (3) triangular-like/trapeziform-like structures of the curve show that ␣-helices and -strands appear alternatively in this region. So from the M-curve, a protein could be directly assigned into corresponding secondary structure class. Moreover, a new numerical descriptor, four-component vector, is introduced and applied to cluster analysis.
The construction of state‐of‐the‐art charge transporting materials (CTMs) is challenging in modulating molecular configurations for simultaneously achieving high thermal stability and appreciable solution processability. Herein, N,N′‐bis(1‐indanyl)naphthalene‐1,4,5,8‐tetracarboxylic diimide (NDI‐ID) is served as a theoretical model to investigate the influence of molecular structure on the tradeoff between thermal stability and solubility. Compared with the alkyl substituted analog, the thermal stability of NDI‐ID is enhanced by the intramolecular and intermolecular short contacts, indicating the conformational rigidity dictates the morphological stability of the film phase. On the other hand, the dynamic topological transformation of material molecules occurs during the solvation process and, where the intramolecular hydrogen bonds are attenuated by the interactions with the surrounding solvent, leads to the increased solubility. The meta‐stable molecular configuration endows NDI‐ID a favorable union of superior solution processability and higher thermal stability, and this insight is also perfectly exemplified by the newly designed CTMs. Therefore, these results reveal the significant role of structural dynamics on material properties, which can provide a new train of thought to develop CTMs for highly efficient and stable perovskite solar cells.
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