Noncovalently fused-ring electron acceptors with near-infrared absorption for high-performance organic solar cells

Abstract

Non-fullerene fused-ring electron acceptors boost the power conversion efficiency of organic solar cells, but they suffer from high synthetic cost and low yield. Here, we show a series of low-cost noncovalently fused-ring electron acceptors, which consist of a ladder-like core locked by noncovalent sulfur–oxygen interactions and flanked by two dicyanoindanone electron-withdrawing groups. Compared with that of similar but unfused acceptor, the presence of ladder-like structure markedly broadens the absorption to the near-infrared region. In addition, the use of intramolecular noncovalent interactions avoids the tedious synthesis of covalently fused-ring structures and markedly lowers the synthetic cost. The optimized solar cells displayed an outstanding efficiency of 13.24%. More importantly, solar cells based on these acceptors demonstrate very low non-radiative energy losses. This research demonstrates that low-cost noncovalently fused-ring electron acceptors are promising to achieve high-efficiency organic solar cells.

Improved Average Figure‐of‐Merit of High‐Efficiency Nonfullerene Solar Cells via Minor Combinatory Side Chain Approach

“…Some nonfused-ring acceptors have been synthesized leading to more simple structures if compared with their similar counterparts, like DC6-IC, DOC2C6-2F, and PTIC. [35,63] Free from complex fusedring structure, PTIC obtained a significantly low SC of 54.62% according to the calculation by Chen et al [35] In addition, optimizations of synthetic routes and reaction yields are also helpful for the realization of low AFOM.…”

Evaporation‐Free Nonfullerene Flexible Organic Solar Cell Modules Manufactured by An All‐Solution Process

“…Therefore, it was inferred that ITIC would be more compatible with PBDB-T, which has lower crystallinity, while ITIC-Th would be more compatible with SMD2, which has higher crystallinity. [75,76] The miscibility variation was further investigated by performing DSC measurement ( Figure S12, Supporting Information). The blend miscibility was estimated using the Flory-Huggins interaction parameter (χ).…”

Electron‐Deficient and Quinoid Central Unit Engineering for Unfused Ring‐Based A1–D–A2–D–A1‐Type Acceptor Enables High Performance Nonfullerene Polymer Solar Cells with High Voc and PCE Simultaneously

“…Taking into account these two factors, SMAs with partially or fully unfused‐ladder ring as π‐conjugated backbone core have recently been proposed as a novel strategy for high‐efficiency and low‐cost concurrently, where the noncovalent intramolecular interaction plays a crucial role on the mediate of molecular planarity. [ 13,53–67 ] Partially unfused‐ladder ring SMAs are constructed by inserting a modified conjugated bridge between the central small fused ring and the IC terminal group. [ 54,57,64–66 ] For example, in 2017, Bo's group reported a pair of the unfused NF‐SMAs with or without use of S–O intramolecular interactions.…”

“…[ 55,56,58–63 ] For instance, Chen and co‐workers recently reported a series of fully unfused ring core‐based NF‐SMAs (such as DF‐PCIC, HF‐PCIC, and OF‐PCIC) with various difluorinated aromatic central group and two cyclopentadithiophene units, which exhibited a nearly planar molecular geometry owing to the F–H noncovalent interaction. The optimized device based on HF‐PCIC with 2,5‐difluorobenzene core unit achieved the best PCE of 11.49% with an open circuit voltage ( V oc ) of 0.91 V. [ 58 ] Just recently, Bo's group reported a series of S–O intramolecular interaction‐based unfused ring SMAs with central 2,5‐bis(alkyloxy)phenylene unit, two cyclopentadithiophene as flanking unit, and two fluorinated IC units, which have achieved the best PCE of 13.2% with V oc of 0.85 V. [ 63 ] These results indicated that the noncovalent bond intramolecular interaction by introducing strong electronegativity atoms can significantly extend the effective conjugated length and broaden the spectrum absorption to enhance photovoltaic performance. However, unfused ring SMAs containing S–O intramolecular interaction have usually been limited to pair with the deep‐lying highest occupied molecular orbital (HOMO) level type wide bandgap polymer donor (such as PM6 and PM7), which is due to the relatively high HOMO energy level of unfused ring SMAs.…”