Double-bridged N–B←N bipyridyl-based airfoil-shaped small molecule dyes: π-bridge regulation on photovoltaic performance

IF 4.1 3区工程技术 Q2 CHEMISTRY, APPLIED Dyes and Pigments Pub Date : 2024-07-02 DOI:10.1016/j.dyepig.2024.112319

Chang Liu, Lunxiang Yin, Xu Wang, Yaru Liu, Yanqin Li

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Abstract

The double-bridged N–B←N bipyridine unit (BNBP) with boron-nitrogen covalent bond and coordination bond can reduce the electronic energy level of the π-conjugated system, resulting in a reduction of band gap and a red shift in the absorption spectrum. Embedding the BNBP building block into organic optoelectronic materials provides a novel possibility in molecule design. In this paper, under the guidance of density functional theory (DFT) calculations, a series of 3D “airfoil-shaped” small molecule donors (SMDs) have been designed and successfully synthesized through Sonogashira, Suzuki and Stille coupling reactions. BNBP is adopted as the central electron-withdrawing unit and strong electron-rich triphenylamine (TPA) as the terminal group. The novel “airfoil-shaped” structure plays a supporting role in reducing the carrier recombination in the active layer. It reveals that molecular design engineering can achieve the expected results by the following steps: Firstly, the introduction of electron-rich alkoxy groups into the end of TPA through side chain engineering helps to improve the solubility and film-forming properties of the materials. Then, the π-bridge regulation not only extends the conjugate structure, but also plays a crucial role in the regulation of photovoltaic properties. It is worth noting that the compound BNBP(3TTPA)₂ was synthesized by introducing thiophene oligomer into BNBP-based SMDs for the first time. Finally, the compound BNBP(EDPPTPA)₂ was constructed by combining BNBP with DPP dye unit. Its narrow band gap is only 1.36 eV, which is one of the narrowest band gaps in small molecular organic-boron materials. In particular, compared with the starting compound BNBP(ETPA)₂, the synergistic effects of DPP and BNBP broaden the edge absorption wavelength to 814 nm, resulting in a red shift of 170 nm. The power conversion efficiency (PCE) of 4.48 % is obtained in BNBP(EDPPTPA)₂-based bulk heterojunction (BHJ) organic solar cells (OSCs), which is more than twice that of reference compound BNBP(ETPA)₂. This work provides important references for the future development of 3D BNBP-based organic-boron SMDs and the structural regulation of materials through molecular engineering.

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双桥 N-B←N 双吡啶基翼形小分子染料：π 桥对光电性能的调控

具有硼氮共价键和配位键的双桥 N-B←N 联吡啶单元（BNBP）可以降低π共轭体系的电子能级，从而导致带隙减小和吸收光谱红移。将 BNBP 构建模块嵌入有机光电材料为分子设计提供了一种新的可能性。本文在密度泛函理论（DFT）计算的指导下，通过 Sonogashira、Suzuki 和 Stille 偶联反应，设计并成功合成了一系列三维 "翼形 "小分子供体（SMDs）。以 BNBP 为中心取电子单元，以强电子富集的三苯胺（TPA）为末端基团。新颖的 "翼形 "结构对减少活性层中的载流子重组起到了支持作用。它揭示了分子设计工程可以通过以下步骤达到预期效果：首先，通过侧链工程在 TPA 末端引入富电子烷氧基，有助于提高材料的溶解性和成膜性能。然后，π桥调控不仅扩展了共轭结构，而且在光伏性能调控中发挥了关键作用。值得注意的是，化合物 BNBP(3TTPA)2 是首次在基于 BNBP 的 SMD 中引入噻吩低聚物而合成的。最后，化合物 BNBP(EDPPTPA)2 是由 BNBP 与 DPP 染料单元结合而成。它的窄带隙仅为 1.36 eV，是小分子有机硼材料中带隙最窄的化合物之一。特别是，与起始化合物 BNBP(ETPA)2 相比，DPP 和 BNBP 的协同作用将边缘吸收波长拓宽到 814 nm，导致红移 170 nm。基于 BNBP（EDPPTPA）2 的体异质结（BHJ）有机太阳能电池（OSC）的功率转换效率（PCE）为 4.48%，是参考化合物 BNBP（ETPA）2 的两倍多。这项工作为未来开发基于三维 BNBP 的有机硼 SMD 以及通过分子工程调控材料结构提供了重要参考。

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来源期刊

Dyes and Pigments 工程技术-材料科学：纺织

CiteScore

8.20

自引率

13.30%

发文量

933

审稿时长

33 days

期刊介绍： Dyes and Pigments covers the scientific and technical aspects of the chemistry and physics of dyes, pigments and their intermediates. Emphasis is placed on the properties of the colouring matters themselves rather than on their applications or the system in which they may be applied. Thus the journal accepts research and review papers on the synthesis of dyes, pigments and intermediates, their physical or chemical properties, e.g. spectroscopic, surface, solution or solid state characteristics, the physical aspects of their preparation, e.g. precipitation, nucleation and growth, crystal formation, liquid crystalline characteristics, their photochemical, ecological or biological properties and the relationship between colour and chemical constitution. However, papers are considered which deal with the more fundamental aspects of colourant application and of the interactions of colourants with substrates or media. The journal will interest a wide variety of workers in a range of disciplines whose work involves dyes, pigments and their intermediates, and provides a platform for investigators with common interests but diverse fields of activity such as cosmetics, reprographics, dye and pigment synthesis, medical research, polymers, etc.