Effect of Bulky Groups on the Performance of Subphthalocyanine‐Based Dye‐Sensitized Solar Cells

Dye‐sensitized solar cells (DSSCs) have remained a promising alternative in photovoltaic technology due to their cost‐effectiveness and adaptability to low‐light conditions. Among the various sensitizers, subphthalocyanines (SubPcs) have emerged as potential candidates due to their nonflat structure, which reduces aggregation and increases solubility. However, their application in DSSCs remains poorly explored. In this study, four new SubPc dyes with different peripheral substituents are synthesized and characterized to evaluate their photovoltaic performance. The best‐performing dye, SubPc 3, exhibits the most redshifted absorption spectrum and achieved a maximum efficiency of 1.69%. Photophysical analyses are conducted using transient absorption spectroscopy and intensity‐modulated photovoltage/photocurrent spectroscopy (IMVS/IMPS). IMVS/IMPS measurements indicate a relatively stable electron population in the semiconductor, with an electron lifetime in the semiconductor significantly longer than the transport time, which leads to a satisfactory charge collection efficiency ( η cc = 0.83). However, ps‐TAS analysis reveals efficiency losses due to competing geminate recombination ( τ grec = 1.264 µs) with the dye regeneration ( τ reg = 0.594 µs) at the origin of photogenerated current limitations. This study provides a basis for future research on SubPc sensitizers, highlighting the importance of mitigating recombination pathways to maximize light absorption and charge separation.