Synthesis and Investigation of Electro-Optical Properties of H-Shape Dibenzofulvene Derivatives

Abstract

We have synthetized two classes of dibenzofulvene-arylamino derivatives with an H-shape design, for a total of six different molecules. The molecular structures consist of two D-A-D units connected by a thiophene or bitiophene bridge, using diarylamino substituents as donor groups anchored to the 2,7- (Group A) and 3,6- (Group B) positions of the dibenzofulvene backbone. The donor units and the thiophene or bithiophene bridges were used as chemico-structural tools to modulate electro-optical and morphological-electrical properties. A combination of experiments, such as absorption measurements (UV-Vis spectroscopy), cyclic voltammetry, ellipsometry, Raman, atomic force microscopy, TD-DFT calculation and hole-mobility measurements, were carried out on the synthesized small organic molecules to investigate the differences between the two classes and therefore understand the relevance of the molecular design of the various properties. We found that the anchoring position on dibenzofulvene plays a crucial key for fine-tuning the optical, structural, and morphological properties of molecules. In particular, molecules with substituents in 2,7 positions (Group A) showed a lower structural disorder, a larger molecular planarity, and a lower roughness.

Dibenzofulvene Derivatives as Promising Materials for Photovoltaic and Organic Electronics

“…Dibenzofulvene derivatives (DBF) have been scarcely described in the literature. However, in the last decade, interest in them has increased significantly (Figure 2) [32][33][34][35][37][38][39][40][41][42][43][44][45][46][48][49][50]. This is largely due to the intensive search for new chemical compounds for applications in photovoltaic and organic electronics.…”

“…First of all, this is due to the many advantages of compounds of this type, such as the possibility of modification through many chemical reactions, excellent thermal stability, the high quantum yield of photoluminescence, relatively good features of molecular self-assembly, ambipolar properties of charge transport (holes and electrons), many peculiar features regarding nonlinear optical properties, as well as very good photostability [40,50]. A very interesting variant of the mentioned compounds are dibenzofulvene derivatives (DBFs) (Figure 1) [32][33][34][35][37][38][39][40][41][42][43][44][45][46][48][49][50]. These compounds largely retain the properties of fluorene and its derivatives.…”

“…However, due to the carbon-carbon double bond (C=C) in the C9 position of fluorene and the additional substituent at the end of this bond, dibenzofulvene derivatives gain additional opportunities to modify their physicochemical properties. Thanks to this, dibenzofulvene derivatives are becoming increasingly popular compounds in various research [32][33][34][35][37][38][39][40][41][42][43][44][45][46][48][49][50].…”

Passivation of Inverted Perovskite Solar Cells by Trifluoromethyl-Group-Modified Triphenylamine Dibenzofulvene Hole Transporting Interfacial Layers

“…Some research employ dibenzofulvene (9-methylene-fluorene) derivatives as hole transporting layers because fluorene is a prominent construction unit for interfacial charge-transporting materials in PSCs . Because of its coplanarity, ordered pi-stacking, and excellent charge mobility, dibenzofulvene that contains fluorene segments has been widely employed as a building block for optoelectronic devices. , The advantages of using this material are its high conversion yield, its being relatively inexpensive, and the straightforward synthesis. , Additionally, some prior works on developing small organic molecule HTMs paired with MAPbI 3 perovskites had been reported and showed an excellent matching on the energy level, as the valance band of the MAPbI3 perovskite (−5.43 eV) was favorable to the organic layer HOMO level; moreover, it provided a significant enhancement of the power conversion efficiency of the device. , …”

“…34,35 The advantages of using this material are its high conversion yield, its being relatively inexpensive, and the straightforward synthesis. 36,37 Additionally, some prior works on developing small organic molecule HTMs paired with MAPbI 3 perovskites had been reported and showed an excellent matching on the energy level, as the valance band of the MAPbI3 perovskite (−5.43 eV) was favorable to the organic layer HOMO level; moreover, it provided a significant enhancement of the power conversion efficiency of the device. 38,39 In this study, we synthesized trifluoromethyl-group-modified triphenylamine dibenzofulvene as hole transporting materials (CC-1−3).…”