Novel polymeric metal complexes of salicylaldehyde schiff base derivative being used for dye sensitizer

Abstract

For studying the effect of metal complexes used as auxiliary electron acceptors of dye sensitizers in dye sensitized solar cell (DSSC) on photovoltaic performance, four polymeric metal complexes, which adopt 1,4-dioctyloxy-2,5-dibromobenzene or thienylbenzo-[1,2-b:4,5-b']-dithiophene (BDTT) as electron donor (D), salicylaldehyde schiff base derivatives as auxiliary acceptor (A), 8-hydroxyquinoline derivative as π bridge and acceptor (A), were designed, synthesized and characterized. The influence of different donor and metal complexes of the four dye sensitizers on performance were discussed by determining their thermal, photophysical, electrochemical and photovoltaic properties. The DSSC devices based on the four polymeric metal complexes PBDTT–SF–Cd, PBDTT–SF–Cu, PPV-SF-Cd and PPV-SF-Cu exhibited a short-circuit photocurrent density (Jsc) of 14.94 mA cm−2, 14.86 mA cm−2, 10.23 mA cm−2 and 9.80 mA cm−2 as well as acquired power conversion efficiency (PCE) of 8.59%, 8.45%, 5.29% and 4.77% respectively under the AM 1.5 irradiation (100 mW cm−2). Both Jsc and PCE value of the four polymeric metal complexes are in a decreased order. The phenomenon is attributed to not only the variable strength of coordination bond formed between metal ion and ligand, which can be affected by the radius and charge number of metal ion, but also the better electron-donating ability of BDTT. In common charge number, bigger radius of metal ion will cause more powerful coordination bond as well as greater electron-withdrawing ability of auxiliary acceptor and charge-transfer ability between donor and acceptor. This work provides a distinctive perspective for the design of D-A-π-A motif complexes in DSSC application.