Synthesis and applications of main-chain Ru(ii) metallo-polymers containing bis-terpyridyl ligands with various benzodiazole cores for solar cells

Abstract

A series of π-conjugated bis-terpyridyl ligands (M1–M3) bearing various benzodiazole cores and their corresponding main-chain Ru(II) metallo-polymers were designed and synthesized. The formation of metallo-polymers were confirmed by NMR, relative viscosity, and UV-visible titration measurements. The effects of electron donor and acceptor interactions on their thermal, optical, electrochemical, and photovoltaic properties were investigated. Due to the strong intramolecular charge transfer (ICT) interaction and metal to ligand charge transfer (MLCT) in Ru(II)-containing polymers, the absorption spectra covered a broad range of 260–750 nm with the optical band gaps of 1.77–1.63 eV. In addition, due to the broad sensitization areas of the metallo-polymers, their bulk heterojunction (BHJ) solar cell devices containing [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) as an electron acceptor exhibited a high short-circuit current (J_sc). An optimum PVC device based on the blended polymer P1 : PCBM = 1 : 1 (w/w) achieved the maximum power conversion efficiency (PCE) value up to 0.45%, with V_oc = 0.61 V, J_sc = 2.18 mA cm⁻², and FF = 34.1% (under AM 1.5 G 100 mW cm⁻²), which demonstrated a novel family of conjugated polyelectrolytes with the highest PCE value comparable with BHJ solar cells fabricated from ionic polythiophene and C₆₀.