Design of Hexabenzocoronene Derivatives as Non-Fullerene Acceptors in Organic Photovoltaics by Bridging Dimers and Modulating Structural Twists

Abstract

Non‐fullerene small molecule (SM) acceptors possess many advantages, such as simple synthesis and purification, easily modulated spectrums and energy levels compared with fullerenes. Herein, a series of acceptor molecules 1–14 based on halogenated hexabenzocoronene derivative (8F‐8Cl‐cHBC) dimers, which could be synthesized in experiment, were rationally designed via benzothiadiazole (BT) bridging and closed rings in cHBC to change structural twists. The electronic structures and energy levels related to open circuit voltage (VOC), as well as the absorption spectra related to short circuit current density (JSC) of 1–14 have been systematically investigated by density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT). Meanwhile, the intermolecular charge transfer rates (kinter‐CT) and charge recombination rates (kinter‐CR) of the interface α‐sexithienyl (6T)/1–14 were investigated by Marcus semi‐classical model. The results revealed that bridging 8F‐8Cl‐cHBC dimers could significantly adjust the energy level, increase the photon collection and form spectral complementarity with donor. The change of closed rings for cHBC units could improve the morphology, adjust π‐π interaction, and form three–dimensional (3D) charge transmission, and thus increased interface electronic transmission channel. Therefore, our designed acceptors will provide a theoretical guideline for designing new non‐fullerene SM acceptors containing bridged dimers and structural twists.

Synthesis, Optical, and Geometrical Approaches of New Natural Fatty Acids’ Esters/Schiff Base Liquid Crystals

“…As can be seen from Figure 7, the present compounds with -N=CH- linkages ( I – III ) exhibit two absorption bands at 274 nm (ε ~ 3.7 × 10 4 L. mol −1 ) and 341 nm (ε ~ 3.2 × 10 4 L. mol −1 ) while the azobenzene derivative ( V ( i – iii )) showed only one electronic transition absorbance peak at 352 nm. These observed peaks may be attributed to the π–π* transition involved in the π-electronic system throughout the whole mesogenic portion, with a suitable charge transfer (CT) property [63,64,65]. The photoisomerization for present compounds has confirmed and occurred in the range of 300–400 nm.…”

The reason why a kind of diketopyrrolopyrrole‐analogue can act as acceptors: Theoretical study and characterization

“…Here, the charge difference densities (CDD) maps are well used to find the intermolecular charge transfer (inter‐CT) excited states, whose hole and electron is totally localized on donor and acceptor, respectively. It is depicted in the CDD maps of Figure . From Figure , the intermolecular charge transfer excited states are S 1 , S 2 , S 3 for PTB7‐Th/ BFT‐SS and S 1 , S 2 , S 3 , S 5 for PTB7‐Th/ BFT‐SS’ , respectively.…”

Thermal and Photophysical Studies of Binary Mixtures of Liquid Crystal with Different Geometrical Mesogens

“…Figures 6-8 display the influence of temperature on the shape and the intensity of the absorption bands for I6+8, II6+8 and their eutectic mixture I6+8/II6+8, respectively. As shown from these figures, all the compounds investigated exhibited an absorption maximum in the range 335-356 nm and weak absorption band at 445 nm, which were related to π-π* and n-π* transitions of the azobenzene trans-cis configuration, respectively [62][63][64]. The Schiff base derivative I6+8 showed a maximum absorption band at ~335 nm, and that absorbance slightly increased with increasing the temperature.…”