Synthesis of donor-π-acceptor porphyrins for DSSC: DFT-study, comparison of anchoring mode and effectiveness

Abstract

In this study two pairs of novel zinc-porphyrin complexes (ZnP1 ZnP2 ZnP3 and ZnP4) were synthesized as sensitizers for DSSC and their photophysical, computational studies and photovoltaic properties were investigated. Structures of proposed dyes are based on a molecular design that relies on donor/[Formula: see text]-bridge/acceptor interactions. Compounds differ by anchoring mode to the titanium dioxide surface: ZnP2 and ZnP4 porphyrins possess carboxyl anchoring groups while ZnP1 and ZnP3 porphyrins have similar structure but without anchors and attached to the surface by isonicotinic acid ligands. All the zinc-porphyrin derivatives bear hexyloxy-chains at the para-positions of their phenyl rings and ZnP3 and ZnP4 contain 1,3,5-triazine fragments as efficient electron transfer bridges. Electron density distribution of the frontier molecular orbitals was calculated based on the density functional theory (DFT). The test DSSC was manufactured and its parameters were measured to compare the effectiveness of the proposed sensitizers. Our results reveal that dyes with an anchoring group directly in their structure demonstrated several times higher efficiency. The use of the triazine fragment proved effective for the introduction of acceptor substituents bearing anchor groups. As a result, the highest efficiency of 4.33% was achieved using the dye ZnP4.