Conjugated Polymers Bearing Iridium Complexes for Triplet Photovoltaic Devices

The aim of this work is to investigate the effect of incorporating an iridium complex into a π-conjugated polymer backbone on photovoltaic properties such as charge generation, power conversion efficiency and external quantum efficiency (EQE). Poly(9,9-dihexylfluorene-co-2-phenylpyridine) ( 1 ) and poly(9,9-dioctylfluorene-co-tris(2-phenylpyridine) iridium (III))) ( 2 ) were synthesized using Suzuki polycondensation. Characterization was performed using NMR, UV−vis, photoluminescence, and time-resolved luminescence spectroscopy; gel permeation chromatography; elemental analysis; and photovoltaic devices. An increase in percent EQE for 2 over 1, from 1.1 to 10.3, is attributed to the formation of the triplet state in ( 2 ), and by inference, longer diffusion lengths of the triplet exciton, compared to the singlet exciton that is formed in ( 1 ).