Unambiguous Diagnosis of Photoinduced Charge Carrier Signatures in a Stoichiometrically Controlled Semiconducting Polymer‐Wrapped Carbon Nanotube Assembly

Abstract

AbstractSingle‐walled carbon nanotube (SWNT)‐based nanohybrid compositions based on (6,5) chirality‐enriched SWNTs ([(6,5) SWNTs]) and a chiral n‐type polymer (S‐PBN(b)‐Ph4PDI) that exploits a perylenediimide (PDI)‐containing repeat unit are reported; S‐PBN(b)‐Ph4PDI‐[(6,5) SWNT] superstructures feature a PDI electron acceptor unit positioned at 3 nm intervals along the nanotube surface, thus controlling rigorously SWNT–electron acceptor stoichiometry and organization. Potentiometric studies and redox‐titration experiments determine driving forces for photoinduced charge separation (CS) and thermal charge recombination (CR) reactions, as well as spectroscopic signatures of SWNT hole polaron and PDI radical anion (PDI−.) states. Time‐resolved pump–probe spectroscopic studies demonstrate that S‐PBN(b)‐Ph4PDI‐[(6,5) SWNT] electronic excitation generates PDI−. via a photoinduced CS reaction (τCS≈0.4 ps, ΦCS≈0.97). These experiments highlight the concomitant rise and decay of transient absorption spectroscopic signatures characteristic of the SWNT hole polaron and PDI−. states. Multiwavelength global analysis of these data provide two charge‐recombination time constants (τCR≈31.8 and 250 ps) that likely reflect CR dynamics involving both an intimately associated SWNT hole polaron and PDI−. charge‐separated state, and a related charge‐separated state involving PDI−. and a hole polaron site produced via hole migration along the SWNT backbone that occurs over this timescale.