Charging and discharging of single conjugated-polymer nanoparticles

Abstract

Despite intense, long-term interest in organic semiconductors from both an applied and fundamental perspective, key aspects of the electronic properties of these materials remain poorly defined. A particularly challenging problem is the molecular nature of positive charge carriers, that is, holes or oxidized species in organics. Here, the unique ability of single-molecule spectroelectrochemistry (SMS-EC) to unravel complex electrochemical process in heterogeneous media is used to study the oxidation of nanoparticles of the conjugated polymer poly(9,9-dioctylfluorene-co-benzothiadiazole). A reversible hole-injection charging process has been observed that occurs primarily by initial injection of shallow (untrapped) holes, but soon after the injection, a small fraction of the holes becomes deeply trapped. Good agreement between experimental data and simulations strongly supports the presence of deep traps in the studied nanoparticles and highlights the ability of SMS-EC to study energetics and dynamics of deep traps in organic materials at the nanoscale.

Electrochemical Control of the Time-Dependent Intensity Fluctuations in Surface-Enhanced Raman Scattering (SERS)

“…[5][6][7][8][9] On the other hand, reports on the investigation of electrode processes in situ by SMS (known as single-molecule spectroelectrochemistrysSM-SEC) are still rare. [10][11][12][13] Moreover, although the main body of electrochemical work is performed using metallic surfaces, all SM-SEC reports to date were on nonmetallic electrodes, such as indium-tin oxide (ITO) 10 and optically transparent carbon 11 electrodes. The main limitation to the implementation of SM-SEC from metal electrodes is the well-known quenching of molecular emissions by metallic surfaces.…”

Single particle spectroscopy on composite MEH-PPV/PCBM nanoparticles

“…These sites are coupled to each other by a fast energy transfer process, showing that even single polymer chains exhibit bulk-like behavior to a certain extent and thus are good simplified model systems to study photophysical processes in conducting polymer bulk materials. More recently, reversible photooxidation and deep charge trapping were investigated for single conducting polymer chains in a functioning device, and Stark shifts of conducting polymer spectra by electrical fields were reported [16,[28][29][30].…”

Heterogeneous Charge Mobility in Individual Conjugated Polyelectrolyte Nanoparticles Revealed by Two-Color Single Particle Spectroelectrochemistry Studies

“…26 We demonstrate that NPs of MPS-PPV display differing emissive behavior when subjected to an externally applied electrochemical bias. This is manifested both in the response speed and modulation amplitude exhibited between different nanoparticles.…”