Enhanced performance of dye-sensitized solar cells with Y-shaped organic dyes containing di-anchoring groups

Abstract

Two new Y-shaped D–π–(A)₂ type phenothiazine-based dyes (ZJA2 and ZJA3) were designed and synthesized for dye-sensitized solar cells (DSSCs). Compared to the single D–π–A analogue dye ZJA1, the Y-shaped dye with two carboxylic acid anchors was in favour of enhancing the performance of DSSCs. The FTIR spectra revealed that the dye ZJA2 molecules were anchored onto the TiO₂ surface by two carboxylic acid anchors, which effectively increased the electron extraction channels. The steady-state emission spectra and time-resolved fluorescence experiments all indicated that the electron injection efficiency of dye ZJA2 was improved by the increased electron extraction channels, thus the J_sc of ZJA2 was greatly improved compared to dye ZJA1. In addition, benzene was used as the π-bridge for linking di-anchoring groups, combined with CDCA, thereby reducing the charge recombination. As a result, the PCE of the DSSC based on ZJA2 (4.55%) was 67% higher than the DSSC based on ZJA1 (2.72%). The Y-shaped D–π–(A)₂ type phenothiazine-based dye ZJA3 containing two pyridine anchors was also investigated, and the DSSC based on ZJA3 showed a poor PCE (0.45%) due to the low dye loading.