Self‐Assembled, Chemically Fixed Homojunctions in Semiconducting Polymers

Abstract

A p–n junction in an organic emissive polymer is chemically fixed through the use of polymerizable ions. This leads to a permanent configuration of compensating ions, unlike dynamic light‐emitting electrochemical cells. The process is demonstrated with red‐, green‐, and blue‐light‐emissive polymers; a photovoltaic effect is also demonstrated.

On-demand photochemical stabilization of doping in light-emitting electrochemical cells

“…The performance of the photochemically stabilized devices is on par, or better, than previously published chemically stabilized LECs, [39][40][41] but a comparison with recently published data on conventional dynamic LEC devices based on the same conjugated polymer SY indicates that further improvements are possible. [50][51][52][53] In chemically stabilized LECs, with no added initiator compound, the cross-linking of the ions and/or ion-transport material is presumably initiated by the electrons/holes on the conjugated polymer.…”

“…[50][51][52][53] In chemically stabilized LECs, with no added initiator compound, the cross-linking of the ions and/or ion-transport material is presumably initiated by the electrons/holes on the conjugated polymer. [39] This has the undesired consequence that the conjugation, i.e. the electron transport paths, of the conjugated polymer will be broken at the initiation places.…”

“…[30][31][32][33][34][35][36] Lonergan and co-workers stabilized a p-n junction at the interface between a cationic and an anionic conjugated polyelectrolyte by solvent-induced removal of the mobile counter-ions, [37] while Bazan et al utilized in-situ boron-fluoride chemistry on a similar device structure for the same purpose. [38] Finally, Leger and Bartholomew [39] conceptualized the more generic "chemical stabilization" approach, which utilizes designed dopant counter-ions that can be physically immobilized via cross-linking polymerization reactions that presumably are initiated by electrochemical means. [39][40][41][42][43] Here, we expand on the latter work and design devices in which the doping stabilization can be conveniently executed by a short UV-light exposure.…”

“…[38] Finally, Leger and Bartholomew [39] conceptualized the more generic "chemical stabilization" approach, which utilizes designed dopant counter-ions that can be physically immobilized via cross-linking polymerization reactions that presumably are initiated by electrochemical means. [39][40][41][42][43] Here, we expand on the latter work and design devices in which the doping stabilization can be conveniently executed by a short UV-light exposure. This is accomplished by including a UV-sensitive photo-initiator material into a tuned active material blend comprising an ion-pair monomer and an iontransport material, both endowed with an acrylic functional group, in addition to the conjugated polymer.…”

Organic Reprogrammable Circuits Based on Electrochemically Formed Diodes

“…Injection of charges into the semiconducting polymers and the charge compensation provided by the ions results in the formation of p-and n-doped regions of the polymer. The resulting p-n junction can be stabilized chemically [11][12][13][14][15] or physically 16- 22 and 3 displays an electronic current rectification property together with a built-in potential 6,23 . The fixed p-n junction stabilized by the physical method, often termed "frozen junction", takes advantage of the temperature-dependent ion mobility in the LECs, i.e., after the desired ion distribution is reached in the device, the temperature is decreased to a point where the ions are effectively immobile.…”