Density functional theory (DFT) and time-dependent DFT calculations have been employed to model Zn meso-tetraphenylporphyrin (ZnTPP) complexes having different β-substituents, in order to design an efficient sensitizer for dye-sensitized solar cells. To calculate the excited states of the porphyrin analogues, at least the TD-B3LYP/6-31G* level of theory is needed to replicate the experimental absorption spectra. Solvation results were found to be invariant with respect to the type of model used (PCM vs.C-PCM). Most of the electronic transitions based on Gouterman’s four-orbital model of ZnTPP-A and ZnTPP-B are π → π* transitions, so that cell efficiency can be enhanced by increasing the π-conjugation and electron-withdrawing capability of the β-substituent. This proposition was tested by inserting thiophene into the β-substituent of ZnTPP-A to form a new analogue, ZnTPP-C. Compared with ZnTPP-A and ZnTPP-B, ZnTPP-C has a smaller band gap, which brings LUMO closer to the conduction band of TiO₂, and a red-shifted absorption spectrum with higher extinction coefficients, especially in the Q-band position.

The application potential of flexible electrochromic materials for wearable devices, smart textiles, flexible displays, electronic paper, and implantable biomedical devices is enormous. These materials offer the advantages of conformability and mechanical robustness, making them highly desirable for these applications. In this review, we comprehensively examine the field of flexible electrochromic materials, covering topics such as synthesis methods, structure design, electrochromic mechanisms, and current applications. We also address the challenges associated with achieving flexibility in electrochromic materials and discuss strategies to overcome them. By shedding light on these challenges and proposing solutions, we aim to advance the development of flexible electrochromic materials. We also highlight recent advances in the field and present promising directions for future research. We intend to stimulate further innovation and development in this rapidly evolving field and encourage researchers to explore new opportunities and applications for flexible electrochromic materials. Through this review, readers can gain a comprehensive understanding of the synthesis, design, mechanisms, and applications of flexible electrochromic materials. It serves as a valuable resource for researchers and industry professionals looking to harness the potential of these materials for various technological applications.