Visualizing the Bipolar Electrochemistry of Electrochemically Doped Luminescent Conjugated Polymers

Abstract

We use a micro-manipulated vacuum probe station to generate and visualize bipolar electrochemical redox reactions in a solid-state polymer light-emitting electrochemical cell (PLEC). In situ electrochemical p-and n-doping of a luminescent polymer is initially induced via a pair of biased metallic probes in direct contact with the luminescent polymer. Subsequently, the biased probes are moved to contact the planar aluminum driving electrodes of the PLEC to activate the device. By analyzing the complex doping patterns generated, we conclude that the doped polymers have functioned as bipolar electrodes (BPEs), from which electrochemical p-or n-doping are induced wirelessly. The potential energy barrier between the polymer BPE and the undoped polymer have played a major role in doping initiation. In a separate planar cell of a smaller gap size, a pair of planar aluminum electrodes was driven in such a way that they functioned as long BPEs to create five coupled and strongly emitting polymer p-n junctions. These results offer vivid visualization of the intriguing bipolar electrochemical phenomena in a solid-state polymer blend. The ability to form a BPE in situ, and in the form of a heavily doped polymer offer innovative ways to modify the doping profiles in molecular devices. The all-polymer BPE also expands the realm of bipolar electrochemistry to beyond that of a conventional liquid cell containing metal or carbon electrodes.

Shaping Electroluminescence with a Large, Printed Bipolar Electrode Array: Solid Polymer Electrochemical Cells with Over a Thousand Light‐Emitting p–n Junctions

“…The 3D ECL cell exhibits fast reaction kinetics and vastly enhanced light output . Recently, polymer‐based LECs (PLECs) offer a solid‐state platform for bipolar electrochemistry research with the demonstration of several unconventional BPE types …”

Wireless Coupling of Conducting Polymer Actuators with Light Emission

“…Prominent examples comprise color change, [20,22] site selective deposition, [23][24][25][26][27] exfoliation, [28] motion, [29][30][31][32][33] light emission [34,35] and chemical read out, [18,36,37] etc. Prominent examples comprise color change, [20,22] site selective deposition, [23][24][25][26][27] exfoliation, [28] motion, [29][30][31][32][33] light emission [34,35] and chemical read out, [18,36,37] etc.…”

“…In general, breaking the symmetry based on bipolar electrochemistry in terms of shape, composition or other physicochemical features of conducting and semiconducting objects is already very well known. Prominent examples comprise color change, [20,22] site selective deposition, [23][24][25][26][27] exfoliation, [28] motion, [29][30][31][32][33] light emission [34,35] and chemical read out, [18,36,37] etc. Bipolar electrochemistry has also been reported to drive electronic devices, [38] leading for example to light emitting eswimmers.…”

Wireless Electromechanical Readout of Chemical Information

“…12,13 BPE is a straight-forward way to break the symmetry of chemical systems and has been used in the past for many applications in various fields ranging from materials science to catalysis and analysis. [14][15][16] It has been employed, among others, to modify conducting or semiconducting objects, [16][17][18][19][20][21][22] allowing an easy access to Janus particles 18,20 , to trigger electrochromism, photoluminescence and electroluminescence in conducting polymers 12,13,[23][24][25] and to generate directional motion or forced propulsion of particles. 21, 22 We recently reported the use of BPE also for the wireless actuation of polypyrrole (PPy) based on an asymmetric volume change.…”