The effect of D–[De–π–A]n (n = 1, 2, 3) type dyes on the overall performance of DSSCs: a theoretical investigation

Abstract

A series of D–[D_e–π–A]_n (n = 1, 2, 3) organic dyes have been theoretically investigated by means of density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches. The influence of inserting extra donor groups (D_e) and multi-branches on the electrical and optical properties as well as the capability of transport performance are expounded through analyzing the geometry, electronic structure, intramolecular charge transfer, reorganization energy, light harvesting and utilization. These results manifest that inserting D_e leads to red-shifted absorption and enhances the J_ph generated by dyes with one branch. Dyes with three branches not only possess considerable transport performance, but strengthen the absorption intensity as expected. Meanwhile, the results also confirm that multi-branches bring different types of transition for a certain state. The interfacial interaction and electron transfer process are elucidated through using charge density difference and a quantum dynamics method. The results suggest that the strong interfacial interaction makes for a fast interfacial electron transfer (IET) rate. Among them, dyes with a Pe group or dyes with one branch exhibit outstanding performance in interfacial interaction. Our work is expected to provide several theoretical guidelines for further designing and screening prospective sensitizers for DSSCs.