Synthesis of conjugated polymers bearing indacenodithiophene and cyclometalated platinum(II) units and their application in organic photovoltaics

With the goal of applying them in organic photovoltaics (OPVs), in this study we synthesized two organometallic alternating conjugated polymers, TPT–TPyPt and TPT–TIqPt, consisting of indacenodithiophene (thiophene/phenylene/thiophene; TPT) and cyclometalated platinum(II) moieties and compared their optical, electrochemical, and photovoltaic properties, their space charge limited currents, and their structures (density functional theory) with those of related platinum-free organic polymers, TPT–TPy and TPT–TIq. The absorption bands of the metal-based polymers were significantly red-shifted relative to those of the metal-free polymers. We fabricated OPVs incorporating blends of these polymers and [6,6]-phenyl-C71-butyric acid methyl ester at various weight ratios. One of these devices exhibited a power conversion efficiency (PCE) of 2.9%, with a short-circuit current density of 7.7 mA/cm2, an open-circuit voltage of 0.78 V, and a fill factor of 0.48, under AM 1.5 G (100 mW/cm2) illumination. To the best of our knowledge, this PCE is the highest reported for a PSC based on a cyclometalated platinum-type polymer.