Improved efficiency by selenophene-substitution for cyclometalated tris-Ir(III) complex based organic solar cells

Organometallic complexes have received insufficient attention in organic solar cells compared to pure organic/polymer counterparts. In this work, based on a previously reported homoleptic tris-Ir(III) complex TBz3Ir, through replacing the central thiophene by selenophene in the cyclometalated ligand of hexylterthiophenebenzo[d]thiazole (TBz), a novel Ir complex of Se-TBz3Ir is developed. Upon Se-substitution, Se-TBz3Ir demonstrates bathochromic-shift absorbance, strengthened light-harvest capacity as well as redshifted and decreased phosphorescence emission in comparison to sulphuric-TBz3Ir. In addition, blending Se-TBz3Ir with Y6 acceptor facilitates to form strong acceptor aggregation domains, which contributes for favourable charge dynamics. Consequently, organic solar cells based on Se-TBz3Ir donor afford outperformed power conversion efficiency of 11.12% compared to 9.97% of the parental TBz3Ir:Y6. The improvement in photovoltaic properties indicates suitable selenophene substitution is an effective strategy for developing high-performance organometallic photovoltaic materials.