School of Chemical Sciences, UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai, Kalina, Santacruz (E), Mumbai 400098, India.
Department of Physics, University of Mumbai, Kalina, Santacruz (E), Mumbai 400098, India.
J Phys Chem B. 2022 Aug 11;126(31):5908-5919. doi: 10.1021/acs.jpcb.2c03952. Epub 2022 Jul 27.
Blends of donors and acceptors have been widely used in bulk-heterojunction solar cells to have exciton formation and charge separation by photoinduced electron transfer (PET). In this work, we have synthesized perylene diimide (PDI)-based materials having different aryl substituents at the bay positions (, , and ) to understand the excited-state dynamics of electron transfer. The detailed photophysics was studied using steady-state as well as ultrafast dynamics of the excited states in different solvents. showed tremendous effects of the solvent on the electronic properties compared with the other two derivatives. The emission quantum yield of decreases drastically in dichloromethane and other polar solvents, indicating strong electron transfer. DFT calculations showed that in the HOMO is centered mostly on the -phenylcarbazole and the LUMO is on the electron-poor PDI moieties. In addition, the energy levels of the HOMO and HOMO-1 in are estimated to be identical. The free energy change for charge separation (Δ) was calculated using electrochemical and photophysical data and found to be negative for The ground- and excited-state dipole moment ratios suggest that the excited state of (1.90) is less polar than that of (3.67), which provides an idea of the lower possibility of charge separation in and . Ultrafast photodynamics studies of , , and showed fast electron transfer only in and not in the other PDI derivatives. It was also observed that electron transfer is faster in DCM and THF than in toluene. Ultrafast dynamics studies showed the presence of an equilibrium between electron transfer and decay from the singlet excited state. Ultrafast studies also showed the features of the -phenylcarbazole cation and PDI anion, further confirming the intramolecular electron transfer in .
供体和受体的混合物已广泛应用于体异质结太阳能电池中，通过光诱导电子转移（PET）实现激子形成和电荷分离。在这项工作中，我们合成了具有不同芳基取代基（，和）的苝二酰亚胺（PDI）基材料，以了解电子转移的激发态动力学。使用稳态和不同溶剂中激发态的超快动力学研究了详细的光物理。与其他两种衍生物相比，显示出溶剂对电子性质的巨大影响。在二氯甲烷和其他极性溶剂中，的发射量子产率急剧下降，表明存在强烈的电子转移。DFT 计算表明，在中，HOMO 主要集中在 -苯基咔唑上，而 LUMO 则在缺电子的 PDI 部分上。此外，的 HOMO 和 HOMO-1 的能级被估计为相同。使用电化学和光物理数据计算了电荷分离的自由能变化（Δ），发现对于为负。基态和激发态偶极矩比表明，的激发态（1.90）比（3.67）的极性更小，这提供了在中电荷分离的可能性较低的想法。，和的超快光动力学研究表明，只有在和中，而不是在其他 PDI 衍生物中，才会发生快速电子转移。还观察到电子转移在 DCM 和 THF 中比在甲苯中更快。超快动力学研究表明，电子转移和从单重激发态的衰减之间存在平衡。超快研究还显示了 -苯基咔唑阳离子和 PDI 阴离子的特征，进一步证实了中的分子内电子转移。
