Electrogenerated Chemiluminescence from Poly(3-hexylthiophene)

Abstract

Electrogenerated chemiluminescence (ECL) from a π-conjugated polymer, poly(3-hexylthiophene) (PAT6), is reported. The pulse electrolysis of a film of PAT6 in an acetonitrile solution of tetrabutylammonium tetrafluoroborate yields a red emission. The ECL spectrum is almost the same as that of photoluminescence of PAT6, indicating that the radiative annihilation of electrochemically formed charged excited states takes place. The mechanism of ECL is discussed in terms of the dynamics of the charged excited species.

Anodic and Cathodic Electrochemically Generated Chemiluminescence in Conjugated Polymers

“…This is because non-completion of the initial polymer doping would lead to a diminished yield of ECL in the subsequent potential pulse. [20] It was found that the doping current density for a thin PPV film drops to less than 0.1 mA cm ±2 (here considered as a practical value of zero current density), in about 0.1 s when the polymer was polarized at E an or E cat . The potentiostatic doping of a polymer is a time-dependent process that requires less than half a second under our experimental conditions, if the current density is considered as the unique parameter for the establish- In fact, temporal analysis of parameters such as mass [56,57] or in-situ conductivity [58] should be also taken into account for the establishment of the equilibrium in these intercalation materials.…”

“…This would explain the diminution of the cathodic ECL efficiency with respect to the anodic one. [20] The analysis of the kinetics of ECL emission will be mostly based on the transport properties of all the charge carriers (electronic and ionic) that are involved in the electrochemical process (step 2). [41] This is because the processes of charge recombination (steps 3±4) and radiative decay of the exciton (step 5) represent extremely fast processes [31,60] on the time scale of the ECL experiment and can be reasonably neglected in the further analysis of ECL kinetics.…”

“…The presence of large, slow charge-compensating anions then favors the occurrence of neutralization as the main electrochemical process also at the beginning of the pulse. [20] …”

“…The acceleration of the electrochemical process improves the ECL yield because this increases the rate of formation of charge carriers from neutral sites at the beginning of the faradic process producing the ECL. [20] …”

“…[17] However, the first investigation on ECL in conjugated polymers was published in 1994, [11] stimulated by the pioneering work of Burroughes et al who reported electroluminescence (EL) from conjugated polymers. [18] So far, only a few studies [11,19,20] have dealt with ECL from a single layer of polymer, and these have shown that light emission is observed mostly in the sequence that produces first the oxidized form of the conducting polymer and then the reduced one. Such unsymmetrical behavior has been associated with the low stability of the polymeric radical anion with respect to the radical cation, [21] and the concomitantly enhanced solubility of the oxidized polymer, which leads to the progressive dissolution of the polymer film in liquid electrolytes.…”