Stepwise Structural Evolution of a DTS-F₂BT Oligomer and Influence of Structural Disorder on Organic Field Effect Transistors and Organic Photovoltaic Performance

Abstract

An A−D−A oligomer, DTS(F 2 BT) 2 , was synthesized; its structural evolution was studied with DSC, POM, 2D-WAXD, and in-situ GI-XRD. The structural evolution of DTS(F 2 BT) 2 is stepwise and kinetically slow. Both rapid drying and the presence of PC 71 BM trapped DTS(F 2 BT) 2 in a less ordered nematic (N) phase. PDMS-assisted crystallization enabled a pristine DTS(F 2 BT) 2 thin film to attain a more ordered equilibrium phase, and enhanced the OFET mobility of DTS(F 2 BT) 2 . In OPV devices, DIO additive drove the DTS(F 2 BT) 2 domains in the DTS(F 2 BT) 2 :PC 71 BM blended film from the N phase toward the equilibrium phase, and resulted in enhanced OPV performances. These results reveal the slow ordering process of the A−D−A oligomer, and the importance of monitoring the degree of structural evolution of the active thin films in organic optoelectronics.

Crystal Engineering of Amphiphilic Organic Dye for Metallic Coloration

“…This result indicated that A 1 GC crystals were preferentially orientated . In the case of the A 1 GC powder state, a homogeneous intensity distribution along the ring was evident from the randomly distributed weak layer orientation . On the low-angle region, a pair of peaks at 2θ = 2.22° ( d = 3.97 nm) was observed with its higher order peaks at 2θ = 4.44° ( d = 1.98 nm).…”

“…39 In the case of the A 1 GC powder state, a homogeneous intensity distribution along the ring was evident from the randomly distributed weak layer orientation. 40 On the low-angle region, a pair of peaks at 2θ = 2.22°(d = 3.97 nm) was observed with its higher order peaks at 2θ = 4.44°(d = 1.98 nm). The q-value ratio for these two peaks was 1:2 indicating the layered structure of the amphiphilic molecules.…”

On the Effect of Confinement on the Structure and Properties of Small‐Molecular Organic Semiconductors

“…p‐ DTS(FBTTh 2 ) 2 is a good candidate for this purpose (as alluded to above) due to its easily accessible melting temperature, which allows cooling from the melt to establish its thermotropic behavior under confinement without significant thermooxidative degradation taking place (see the Supporting Information for details). This material has also been shown to display a rich phase behavior, including liquid crystalline mesophases, in addition to a thermodynamically favored crystal phase . As confining media, we employed electrochemically grown nanoporous anodic aluminum oxide (AAO) comprising nanopores of 25, 40, 60, 180, and 400 nm in diameter, with a 100 µm pore length (scanning electron microscopy (SEM) images of these AAO templates are presented in Figure S1a–f, Supporting Information).…”

“…This raises the question why the mesophase only forms in pores smaller than 60 nm in diameter. Since p‐ DTS(FBTTh 2 ) 2 and other molecules with similar chemical structure were suggested to transiently form liquid‐crystalline phases in the bulk p‐ DTS(FBTTh 2 ) 2 , we hypothesize that the presence of mesophases may be natural to this material but generally is challenging to detect because the transition temperatures of the mesophase formation ( T m,c ) and destruction ( T m,h ) are too close to those of the crystalline phase ( T c and T m , respectively). In contrast, the crystallization and melting processes of strongly confined p‐ DTS(FBTTh 2 ) 2 (i.e., in pores with diameter <60 nm) are shifted to lower temperatures, allowing the mesomorphic phase to be clearly observed.…”

n-Type Thin-Film Transistors Based on Diketopyrrolopyrrole Derivatives: Role of Siloxane Side Chains and Electron-Withdrawing Substituents

“…Although the DSC thermogram of DPPT-Si-INCN did not reveal any endothermic or exothermic transition, the GI-WAXS results suggested that it forms a liquid crystalline (LC) state. 32 Analogous ethylhexyl (−EH) derivatives such as DPPT-EH-DCV 5 did not show any exothermic phase transition during their cooling from the melted state. However, the clear exothermic peak in the DPPT-Si-DCV thermogram indicated that the siloxane side chains, compared to the −EH side chains, can lower the crystallization barrier and can introduce enantiotropic phase behavior to the DPPT−Si series.…”