Ladder‐Type Heteroheptacenes with Different Heterocycles for Nonfullerene Acceptors

Abstract

The design, synthesis,a nd characterization of two novel nonfullerene acceptors (M8 and M34) based on laddertype heteroheptacenes with different heterocycles are reported. Replacing the furan heterocycles with the thiophene heterocycles in the heteroheptacene backbone leads to ahypsochromically shifted absorption band and greatly improved carrier transport for the resulting nonfullerene acceptor (M34) although the p-p-stacking distances are barely affected. Bulk-heterojunction polymer solar cells fabricated from M34 and aw ide band gap polymer (PM6) as the donor showed ab est power conversion efficiency (PCE) of 15.24 %w ith an open circuit voltage (V OC)of0.91 V, muchhigher than aPCE of 4.21 %a nd aV OC of 0.83 Vf or the counterparts based on M8:PM6. These results highlight the importance of key atoms in the construction of high-performance nonfullerene acceptors.

High‐Performance Ladder‐Type Heteroheptacene‐Based Nonfullerene Acceptors Enabled by Asymmetric Cores with Enhanced Noncovalent Intramolecular Interactions

“…We also calculated the HOMA (harmonic oscillator model of aromaticity) value of individual rings for three different heteroheptacene cores (Figure S2). According to the sum of ∑ HOMA values, the global aromaticity of the three cores can be estimated, [29] and their ∑ HOMA indices are basically the same (5.34, 5.30, and 5.28 for MQ3, MQ5, and MQ6, respectively) although the incorporation of selenophene heterocycles did lead to slightly decreased global aromaticity, as expected, in comparison with that based on thiophene heterocycles (5.694 for M34) [23a] . Especially, the switch of selenium atoms in the outer and inner positions of the heteroheptacene cores barely changes their ∑ HOMA indices.…”

An Electron Acceptor Analogue for Lowering Trap Density in Organic Solar Cells

“…[1][2][3][4][5][6][7][8] Since Zhan and co-workers developed ITIC [9] and its derivatives [10][11][12][13] as electron acceptors for BHJ OSCs in 2015, fused ring electron acceptors (FREAs) have replaced the fullerenes to dominate electron acceptors in organic photovoltaics and then greatly boost the development on efficiency and stability of OSCs. Until now, the power conversion efficiencies (PCEs) of OSCs employing high performance polymer donors (like PM6, [14] PM7, [15] D18, [16] and PM6-Tz20 [17] ) and FREAs (such as Y6, [18] M34, [19] and BTP-4Cl [20] ) have reached over 16-17% for single-junction OSCs. However, the device efficiency of OSCs is still much lower than those of inorganic/hybrid solar cells, such as crystalline silicon, [21] and hybrid perovskite.…”

Enhancing the Photovoltaic Performance of Ladder‐Type Heteroheptacene‐based Nonfullerene Acceptors by Incorporating Halogen Atoms on Their Ending Groups

“…The dialdehyde intermediate BDTPT‐CHO was synthesized according to the procedure reported by us previously. [ 32 ] Condensation reactions between BDTPT‐CHO and INCN, INCN2Cl, and INCN2Br in chloroform afforded the corresponding acceptors M5, M6, and M7 in 82%, 85%, and 84% yields, respectively. All the acceptors were characterized by 1 H NMR, 13 C NMR, elemental analysis and high‐resolution mass spectrometry (Supporting Information).…”

“…Very recently, our group reported a novel type of ladder‐type heteroheptacene cores which are free of the sp 3 ‐hybridized bridging carbons. [ 32–35 ] The aggregation and crystalline properties of these heteroheptacene‐based nonfullerene acceptors can be controlled by modulating the size of the neighboring side‐chains as well as the aromaticity (aromatic stabilization energy) of the heteroheptacene core. Through reducing the ππ interaction (or stacking) distance, the resulting nonfullerene acceptor (M36) showed enhanced charge transport and therefore a greatly boosted PCE of 16%, demonstrating the great potential of these ladder‐type heteroheptacene cores for efficient nonfullerene acceptors.…”