Bistetracene Thin Film Polymorphic Control to Unravel the Effect of Molecular Packing on Charge Transport

Abstract

Polymorphism, the ability for a given material to adopt multiple crystalline packing states, is a powerful approach for investigating how changes in molecular packing influence charge transport within organic semiconductors. In this study, a new “thin film” polymorph of the high‐performance, p‐type small molecule N‐octyldiisopropylsilyl acetylene bistetracene (BT) is isolated and characterized. Structural changes in the BT films are monitored using static and in situ grazing‐incidence X‐ray diffraction. The diffraction data, combined with simulation and crystallographic refinement calculations, show the molecular packing of the “thin film” polymorph transforms from a slipped 1D π‐stacking motif to a highly oriented and crystalline film upon solvent vapor annealing with a 2D brick‐layer π‐stacking arrangement, similar to the so‐called “bulk” structure observed in single crystals. Charge transport is characterized as a function of vapor annealing, grain orientation, and temperature. Demonstrating that mobility increases by three orders of magnitude upon solvent vapor annealing and displays a differing temperature‐dependent mobility behavior.

Fluorination Effects on Indacenodithienothiophene Acceptor Packing and Electronic Structure, End-Group Redistribution, and Solar Cell Photovoltaic Response

“…Solid state ordering plays a critical role in defining both the strength and directionality of electronic coupling interactions in organic semiconductors. − Despite the complex and often predominantly amorphous nature of BHJ photoactive layers, the analysis of molecular single-crystal packing provides complementary insight into structure/self-assembly relationships that can assist in both the rational design of new materials and in the understanding of their charge transport properties in BHJ blends. , Currently, however, there is a surprising paucity of single-crystal structural data for IDTT-derived acceptors, including ITIC-4F, considering their broad functionality and fundamental importance. Consequently, single-crystals of ITIC-0F, ITIC-2F, ITIC-4F, ITIC-6F, and a cocrystal of ITIC-0F with ITIC-4F were grown via slow vapor diffusion, and diffraction data were then acquired (see SI for complete detail)…”

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

“…Single crystal X‐ray diffraction techniques were used to determine the packing information at the atomic level to understand the electron transport behaviors and provide an insight into the relationship between structures and properties. [ 59–62 ] In recent years, researchers explored series of single crystal structures used as OSC acceptors, including the perylene diimide‐type, [ 36,38 ] the A‐D‐A‐type, [ 37,39–53 ] the A‐DAD‐A‐type [ 54–57 ] and non‐covalently fused‐ring‐type, [ 41 ] which are summarized in Figure 2 . Wang's group revealed the influence of isomerization on molecular packing arrangements and its photovoltaic performance in the perylene diimide‐type system.…”

Impact of packing arrangement on the optical properties of C60 cluster aggregates

“…Materials made from organic π -conjugated molecules (for instance, fullerenes and their derivatives) 1–3 have attracted much attention over the past few years as the active components in optoelectronic devices including field-effect transistors, solar cells, and light-emitting diodes, to mention a few examples. Among fullerenes, C60 buckminsterfullerene has attracted much attention due to its application in new bulk heterojunction organic solar cells 4–15 due to the unique properties, including high electron mobility, suitable band gaps, and good compatibility with other semiconducting materials. In a related context, optical excitations in π -conjugated molecules depend strongly on the packing configuration of the basic building blocks.…”