AbstractIn this study, we introduce a novel family of symmetrical thiophene‐based small molecules with a Donor‐Acceptor‐Donor structure. These compounds feature three different acceptor units: benzo[c][1,2,5]thiadiazole (Bz), thieno[3,4‐b]pyrazine (Pz), and thieno[1,2,5]thiadiazole (Tz), coupled with electron donor units based on a carbazole‐thiophene derivative. Using Density Functional Theory (DFT), we investigate how the molecular geometry and strength of the central acceptor unit impact the redox and spectroscopic properties. Notably, the incorporation of Pz and Tz moieties induces a significant redshift in the absorption and emission spectra, which extend into the near‐infrared (NIR) region, simultaneously reducing their energy gaps (~1.4–1.6 eV). This shift is attributed to the increased coplanarity of the oligomeric inner core, both in the ground (S0) and excited (S1) states, due to the enhanced quinoidal character as supported by bond‐length alternation (BLA) analysis. These structural changes promote better π‐electron delocalization and facilitate photoinduced charge transfer processes in optoelectronic devices. Notably, we show that Pz‐ and Tz‐containing molecules exhibit NIR electrochromic behavior and present ambivalent character in bulk heterojunction (BHJ) solar cells. Finally, theoretical calculations suggest that these molecules could serve as effective two‐photon absorption (2PA) probes, further expanding their potential in optoelectronic applications.
摘要 在本研究中,我们介绍了一个具有供体-受体-供体结构的新型对称噻吩基小分子系列。这些化合物具有三种不同的受体单元:苯并[c][1,2,5]噻二唑(Bz)、噻吩并[3,4-b]吡嗪(Pz)和噻吩并[1,2,5]噻二唑(Tz),以及基于咔唑-噻吩衍生物的电子供体单元。我们利用密度泛函理论(DFT)研究了中心受体单元的分子几何形状和强度如何影响氧化还原和光谱特性。值得注意的是,加入 Pz 和 Tz 分子后,吸收光谱和发射光谱发生了显著的重移,延伸到了近红外(NIR)区域,同时缩小了能隙(约 1.4-1.6 eV)。这种偏移归因于低聚物内核共面性的增加,无论是在基态(S0)还是激发态(S1),都是由于键长交替(BLA)分析支持的增强的类醌特性。这些结构变化促进了π电子脱ocal,有利于光电器件中的光诱导电荷转移过程。值得注意的是,我们发现含 Pz 和 Tz 的分子表现出近红外电致变色行为,并在体异质结(BHJ)太阳能电池中呈现出矛盾特性。最后,理论计算表明,这些分子可以作为有效的双光子吸收(2PA)探针,进一步拓展它们在光电应用中的潜力。