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).