High‐Performance Nonfused Ring Electron Acceptors with V‐Shaped Side Chains

Abstract

Previously, conjugated polymers and fullerene derivatives as the light absorption layer (or active layer) are mainly used to fabricate OSCs. [7] However, fullerene derivatives have some inherent disadvantages, such as high-cost, [8,9] weak absorption, [10,11] nonadjustable energy levels, [12,13] etc. In recent several years, researchers have turned their attention to nonfullerene acceptors (NFAs). Among them, fused ring electron acceptors (FREAs) play dominate roles in NFAs. [14] Generally, FREAs comprise a large electron-rich ladder-type core unit, forming strong ICT with electron-withdrawing end-groups. [14][15][16] Besides, the bulky side chains of FREAs can suppress the aggregation and ensure the acceptor molecules good solubilities. [17,18] Nowadays, the power conversion efficiencies (PCEs) of single and tandem junction OSCs based on FREAs have exceeded 19% [19] and 20% [20] respectively. However, the synthesis of FREAs often needs multi-steps and involves low-yield ring-closing reactions, resulting in high-cost and intensive labor consuming. [21,22] To solve this dilemma, nonfused ring electron acceptors (NFREAs) have received more and more attention recently, which can be modularly synthesized with several steps and greatly reduce the cost of preparation. [23][24][25] At present, the highest PCE of OSCs based on NFREAs is less than 16%, which still stays behind ones based on FREAs. [26] It is necessary to design and synthesize NFREAs with simple structures and high PCEs.Herein, two isomeric NFREAs o-TT-Cl and m-TT-Cl are designed and synthesized with different lateral substituents. Density functional theory (DFT) calculations reveal that these two acceptors both display nearly planar molecular backbones. Differently, o-TT-Cl has a "V" shaped substituent, which distributes at two sides of the molecular backbone. In comparison, m-TT-Cl has a straight substituent, which distributes at only one side of the molecular backbone. Due to the different lateral substituents, o-TT-Cl and m-TT-Cl display different properties, such as solubilities, molecular packing, charge transport mobilities, etc. At last, o-TT-Cl-based OSCs give a PCE 12.84%, which is much higher than that of m-TT-Cl-based ones. This work provides a valuable highperformance molecular design strategy based on side-chain engineering. Motivatedby simplifying the synthesis of nonfullerene acceptor and establishing the relation between molecular structure and photovoltaic performance, two isomeric nonfused ring electron acceptors (o-TT-Cl and m-TT-Cl), whose properties can be adjusted by changing the side chains, are designed and synthesized with several high-yield steps. o-TT-Cl with V-shaped side chain induces a dominated J-aggregation and displays much better solubility and more ordered packing than m-TT-Cl with linear side chain. Thus, the o-TT-Cl-based blend film generates better phase morphology and charge transport than m-TT-Cl-based one. Finally, the power conversion efficiency of o-TT-Cl-based devices is 12.84%, which is much higher than that of...

A hybrid of MIL-53(Fe) rhombus and conductive CoNi2S4 nanosheets as a synergistic electrocatalyst for the oxygen evolution reaction

“…The LSV after ECSA normalization was calculated according to the equation: ECSA normalized current density = LSV × C s /C dl , where C s is the specific capacitance, and its value was taken as 0.06 mF cm −2 according to previous reports. 47,48 As shown in Fig. S4, † the corrected LSV curve still maintains the same trend as the initial curve, which indicates that the active sites from MIL-53 (Fe)@CoNi 2 S 4 /NF display stronger intrinsic activity than Ir/C for the active site.…”

Effect of Steric Hindrance at the Anthracene Core on the Photovoltaic Performance of Simple Nonfused Ring Electron Acceptors

“…In respect of molecular structures, the high-performance nonfullerene acceptors are usually of A-D-A or A-DA′D-A-type chemical structures. − These specific molecular features can induce a strong dipole moment and push the absorption spectrum to the near-infrared region, which is favorable for improving molecular packing and photon utilization. − However, nonfullerene acceptors sometimes suffer from low solubility, oversized packing, and the existence of large aggregates in blend films due to the too strong intermolecular interactions. − Generally speaking, there are several molecular design strategies to solve this problem. First, the introduction of bulky side chains, for example, ITIC with sp 3 hybrid aromatic chains as well as PTIC with sp 2 hybrid alkoxy and alkyl chains.…”

Easily Available High‐Performance Organic Solar Cells by Regulating Phenylalkyl Side Groups of Non‐Fused Ring Electron Acceptors

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