Crystal Engineering of Organic Optoelectronic Materials

Abstract

Crystal engineering can be regarded as the highly ordered and complicated supramolecular synthesis of functional crystalline solids by control of intermolecular interactions. As one of the most important organic solids for crystal engineering, organic optoelectronic materials have received tremendous interest in the past several decades. In this review, we discuss systematically how to design organic optoelectronic materials from the perspective of crystal engineering including molecular structures, intermolecular interactions, packing arrangements, crystal growth, and patterning methods as well as two-component and multi-component molecular materials. We underline the correlations among molecular structures, packing modes, crystal morphologies, and optoelectronic properties. Finally, we address several key points for further exploration in this field.

Crystal Engineering in Organic Photovoltaic Acceptors: A 3D Network Approach

“…The packing arrangements and intermolecular interactions of molecules in the solid state measured by single crystal X‐ray studies are often used to explore and design the materials with expected physicochemical properties. This research involve the fields of chemistry, pharmacology, and material science, [ 22 ] and is familiar with devices such as organic light‐emitting transistors, [ 23 ] perovskite solar cells [ 24 ] organic field‐effect transistors, [ 25 ] chiral catalytic synthesis, [ 26 ] and molecular magnet assembly. [ 27 ] The packing modes of molecules are generally divided into H‐ and J‐aggregates, [ 28 ] Figure 1 a shows the H/J‐aggregation states and their energy relationships: [ 29 ] an H‐aggregate is the state of conjugated units whose centers face each other, forming an aggregation state with a slightly higher energy, and manifested as a new aggregation absorption peak in the short wavelength range of UV–visible absorption spectrum; a J‐aggregate is a state of conjugated units centrally parallel but inclined to a certain extent, and with a slightly lower energy, which is manifested as a new aggregation absorption peak in the long wavelength range.…”

“…This result indicates that slight changes in intermolecular interaction have a great influence on the aggregation states, and this in turn, affects the physical and chemical properties of the molecules. Organic optoelectronic functional materials are mainly composed of conjugated small organic molecules or macromolecules, which form different aggregation states through intermolecular interactions such as π∙∙∙π interactions (2–10 kcal mol −1 ), hydrogen bonds (1–40 kcal mol −1 ), halogen bonds (1–42 kcal mol −1 ) and van der Waals interactions (0.25–2 kcal mol −1 ) et al., [ 22 ] resulting in different optical, electrical and magnetic properties which attract increasing attention from academia and industry. Here, halogen bonds was defined as when there is evidence of a net attractive interaction between a nucleophilic region of a molecule X and an electrophilic region on a halogen atom Y, where the X can be the Lewis bases of N, O, S, Se, and the Y can be F, Cl, Br, and I atoms etc.…”

“…Here, halogen bonds was defined as when there is evidence of a net attractive interaction between a nucleophilic region of a molecule X and an electrophilic region on a halogen atom Y, where the X can be the Lewis bases of N, O, S, Se, and the Y can be F, Cl, Br, and I atoms etc. [ 22 ] From single‐crystal analysis, if the distance between two atoms is less than the sum of their van der Waals radii, it is considered that there is a non‐covalent interaction between them. Consequently, it is important to understand and adjust the intermolecular interactions and aggregation states of materials by single crystal analysis.…”

Crystal Engineering of 1D Exciton Systems Composed of Single‐ and Double‐Stranded Perylene Bisimide J‐Aggregates

“…Crystal engineering of π‐scaffolds in general [ 1–6 ] and of perylene bisimides (PBIs) in particular [ 7–9 ] has a long tradition. For several decades PBI functional material research was focused on the control of coloristic properties to afford high grade color pigments with hues from red to maroon by tuning the lateral and rotational displacement of the cofacially stacked chromophores.…”

Tunable Mechanical and Optoelectronic Properties of Organic Cocrystals by Unexpected Stacking Transformation from H- to J- and X-Aggregation

“… 29 , 30 Extensive efforts have been made to understand how the stacking mode affects the optoelectronic functions of π-conjugated materials in different molecular systems. 17 , 20 , 31 − 36 However, since observing the stacking transformation of a specific molecule in solid-state crystals is highly challenging, it is extraordinarily difficult to predict the performance of a specific molecule at different stacking modes. Moreover, hybrid stacking might confer synergic and collective effects on the optoelectronic functions.…”