Maredi Swetha, Thakur Diksha, Boruah Dhruba Jyoti, Nayak Sandhya Rani, Yuvaraj Panneerselvam, Vaidyanathan Sivakumar
Department of Chemistry, Indian Institute of Technology, Hyderabad, Kandi, Sangareddy, Telangana, 502285, India.
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
Chem Asian J. 2025 Jun;20(12):e202500152. doi: 10.1002/asia.202500152. Epub 2025 May 6.
Design and synthesis of the fluorophores with tailored emission is critical for advanced optoelectronic applications, including white LEDs. Here in this study, we synthesized benzo[d]thiazole-based donor-acceptor-donor (D-A-D) systems to achieve efficient fluorophores with tunable-emission properties. Three luminogens (based on triphenylamine, diphenylamine, and carbazole as donor units and benzo[d]thiazole as acceptor units) were designed, synthesized, and explored as phosphors for white LEDs. Single-crystal X-ray diffraction revealed significant twisting in the molecular geometries. These twisted structures effectively reduced conjugation, which resulted in a greenish-blue emission in nonpolar solvents. The photophysical properties of these compounds were investigated through solvatochromism experiments and Lippert-Mataga plots, and the study reveals that the compounds have a hybridized local and charge transfer (HLCT) character in their excited states. Lifetime studies revealed mono- and bi-exponential decay. Density functional theory (DFT) calculations were performed to optimize the geometries, and a close match between the theoretical and single-crystal structures was observed. Further, the selected luminogens were integrated with a red-emitting Eu(III) phosphor and PMMA matrix to fabricate a white light-emitting diode (LED). The white LED device exhibited a color rendering index (CRI = 74), excellent chromaticity coordinates (x = 0.29, y = 0.30), a correlated color temperature (CCT = 7207 K), and a luminous efficacy of radiation (LER = 320 lm/W). We observed that introducing an additional diphenylamine donor in the D-A-D system (Py-28-2) enhanced the absolute PLQY to 46.33%. These results demonstrate the potential of these donor-acceptor systems for applications in opto-electronics and lighting technologies.
设计和合成具有定制发射特性的荧光团对于包括白光发光二极管在内的先进光电子应用至关重要。在本研究中，我们合成了基于苯并[d]噻唑的供体-受体-供体（D-A-D）体系，以实现具有可调发射特性的高效荧光团。设计、合成并研究了三种发光体（以三苯胺、二苯胺和咔唑作为供体单元，苯并[d]噻唑作为受体单元）作为白光发光二极管的磷光体。单晶X射线衍射显示分子几何结构存在明显扭曲。这些扭曲结构有效地减少了共轭，导致在非极性溶剂中发出绿蓝色光。通过溶剂化显色实验和Lippert-Mataga图研究了这些化合物的光物理性质，研究表明这些化合物在激发态具有杂化局域和电荷转移（HLCT）特性。寿命研究揭示了单指数和双指数衰减。进行了密度泛函理论（DFT）计算以优化几何结构，并观察到理论结构与单晶结构之间的紧密匹配。此外，将所选发光体与发红光的Eu(III)磷光体和聚甲基丙烯酸甲酯（PMMA）基质集成，以制造白光发光二极管（LED）。该白光LED器件表现出显色指数（CRI = 74）、优异的色度坐标（x = 0.29，y = 0.30）、相关色温（CCT = 7207 K）和辐射发光效率（LER = 320 lm/W）。我们观察到在D-A-D体系中引入额外的二苯胺供体（Py-28-2）可将绝对PLQY提高到46.33%。这些结果证明了这些供体-受体体系在光电子和照明技术应用中的潜力。
