Novel and high photovoltaic performance sensitizers of copolymeric sulfur coordination metal complexes of benzimidazolyl benzodithiophene derivatives

Abstract

To promote the ability of push–pull electrons in D–A′–π–A motif photoelectric sensitizers and to improve their photovoltaic performance, metal complexes with the sulfur coordination of benzimidazolyl benzodithiophene derivatives were used as the unit of auxiliary electron acceptors (A′) of sensitizers, and relevant five novel copolymeric sulfur coordination metal complexes (BDTT–BDTD–Ni, BDTT–BDTD–Cu, BDTT–BDTD–Zn, BDTT–BDTD–Cd, BDTT–BDTD–Hg) were designed, synthesized and characterized. In these sensitizer molecules, 8-quinolinol derivatives were used as a π-bridge and electron acceptor (A), and thienylbenzene-[1,2-b:4,5-b′] dithiophene (BDTT) was used as the electron donor (D). Under a light intensity of 100 mW cm⁻² irradiation, the test results of photovoltaic performance for five copolymeric metal complex sensitizers were that the short circuit current densities (J_sc) are 11.49, 14.09, 15.54, 18.29 and 19.17 mA cm⁻² respectively, and the power conversion efficiency (PCE) are 5.93%, 7.40%, 8.38%, 10.13% and 10.96%, respectively, and their thermal decomposition temperature (T_d) are 302, 309, 295, 301 and 317 °C, respectively. The highest PCE reached 10.96% of BDTT–BDTD–Hg and exceeded 10%. The results showed that the J_sc and PCE values of the copolymeric complexes of the synperiodic metals increased successively from BDTT–BDTD–Ni to BDTT–BDTD–Cu to BDTT–BDTD–Zn, and the J_sc and PCE of the copolymeric complexes of metals in the identical cluster also increased successively from BDTT–BDTD–Zn to BDTT–BDTD–Cd to BDTT–BDTD–Hg, which indicates that the J_sc and PCE of copolymeric metal complexes are associated with the strength of the coordination bonds between the metal and sulfur coordination, and the stronger the coordination bonds, the higher the J_sc and PCE of the copolymeric sulfur coordination metal complexes. These findings provide a good basis for the development of relevant sensitizers in the future.