Explaining the Cyclic Voltammetry of a Poly(1,4‐phenylene‐ethynylene)‐alt‐poly(1,4‐phenylene‐vinylene) Copolymer upon Oxidation by using Spectroscopic Techniques

Abstract

Poly(1,4-phenylene-ethynylene)-alt-poly(1,4-phenylene-vinylene) (PPE-PPV) copolymers have attracted quite a lot of attention in the last few years for electronic device applications owing to their enhanced fluorescence. In this work, we focus on one particular PPE-PPV copolymer with dissymmetrically substituted 1,4-phenylene-ethynylene and symmetrically substituted 1,4-phenylene-vinylene building units. Six successively performed cyclic voltammograms are presented, measured during the oxidation reactions. As the oxidation onset of the electrochemical reaction shifts to lower potentials in each cycle, this behavior is elucidated by using spectroscopic techniques ranging from UV/Vis/near-IR to mid-IR including spin-resonance techniques. Hence, these findings help to explain some of the copolymer's most advantageous properties in terms of possible oxidation products.

Correlated, Dual‐Beam Optical Gating in Coupled Organic–Inorganic Nanostructures

“…This is further supporting evidence for a modified electronic structure of PAE‐ 1 upon binding to PbS NCs since pure, solid PAE‐ 1 exhibits a single, broad fluorescence band centered around 600 nm, which disappears completely upon excitation at 530 nm (Supporting Information, Figure S9). We attribute the induced absorption at 610 nm in PbS‐PAE‐ 1 to the formation of a polaron and note that (O‐alkyl)‐PAE derivatives are indeed known to exhibit polaronic bands in this spectral region . However, activation of these transitions requires direct excitation of the PAE, which is not possible with 1100 nm light.…”

“…The relative positions of the energy levels are inferred from reported literature values of the isolated constituents and under the assumption of vacuum‐level alignment (−5.0 eV/−4.0 eV for the PbS 1S h /1S e states and −6.3 to −5.8/−3.6 to −3.9 eV for the HOMO/LUMO of PAE‐ 1 ; all values against vacuum level) . The polaron gap (P 1 →P 2 ) is reported with 1.9 eV, lifting the P 2 level into close proximity with the 1S e state . Scheme a marks the charge transfer from an excited NC onto the polymer.…”

“…[25] Thep olaron gap (P 1 !P 2 )i sr eported with 1.9 eV,l ifting the P 2 level into close proximity with the 1S e state. [23,24] Scheme 1a marks the charge transfer from an excited NC onto the polymer.This populates the polaronic P 2 level, indicating ac harged polymer with altered electronic structure. [26] This charge transfer enforces excited-state absorption from the polaronic ground state (Scheme 1b) and activates the material for absorption of light between 500-800 nm (brown arrow) to result in an excited-state polaron (Scheme 1c).…”

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

“…In OLED application, the energy level values are necessary to enable the use of the correct host for the emitter in a thermally activated delayed fluorescence (TADF) guest-host system or to decide with which compounds the exciplex donor-acceptor layer could be formed and what additional layers (electron transporting layer (ETL), hole transporting layer (HTL), electron blocking layer (EBL), and hole blocking layer (HBL)) will be necessary to synthesize stable efficiently charged balanced OLED devices 11 12 13 14 15 16 17 . Additional electrochemical measurements allow the investigation of possible side reactions during the process of degradation of the active layer and the formation of low mobile charge carriers (bipolarons) 18 19 20 21 22 .…”

“…Coupling electrochemical and spectroelectrochemical methods allows for easy, accurate, and reliable determination of the degree of oxidation or reduction of conjugated compounds and their degradation potential, which is crucial for stability 23 24 25 26 27 28 . Ultraviolet-visible and near-infrared (UV-Vis-NIR) spectroscopy coupled with electrochemistry can characterize the fundamental chromatic properties of all new conjugated compounds, such as the changing of the absorption band during doping 18 19 20 21 22 23 24 25 26 27 28 29 30 .…”