Theoretical Investigation on Effect of Thiophene and DTS Conjugated Bridges on the Photophysical Properties of Asymmetric Squaraine Dyes for Dye‐Sensitized Solar Cells

ABSTRACT Recently asymmetric squaraine dyes have drawn considerable interest for dye‐sensitized solar cells (DSSCs) owing to their strong absorption spanning the visible to near‐infrared region, remarkable molar extinction coefficients, and versatile structural. However, some squaraine dyes still suffer from limitations, such as narrow spectral coverage and insufficient intramolecular charge transfer (ICT), which adversely affect the power conversion efficiency (PCE) of the dyes. Here, two new molecules, AK4‐S and AK4‐DTS, are constructed by introducing conjugated bridges between the D2 moiety and the anchoring group of the reference dye AK4. Employing density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT), the computational study revealed that incorporating a π‐conjugated spacer can reduce the energy gap (Eg), broaden the absorption spectrum, enhance the oscillator strength (f), suppress charge recombination, improve thermal stability, and significantly promote the ICT process, thereby facilitating electron injection into the TiO 2 substrate. Among them, AK4‐DTS demonstrated the best performance, achieving a theoretical PCE of 9.946%, which is markedly higher than that of the original AK4 (9.050%). These findings demonstrate that incorporating a π‐conjugated bridge serves as a viable approach to improve the PCE of squaraine‐based dyes, thereby providing key guidance for the development of high‐performance sensitizers in DSSCs.