Investigating Work Function Tunable Hole-Injection/Transport Layers of Electrodeposited Polycarbazole Network Thin Films

Abstract

Electrochemical doping properties and morphology changes of electropolymerized poly(N-vinylcarbazole) (PVK) thin films were investigated toward improved hole-injection/transport properties in polymer light emitting diode (PLED) devices. The conjugated network polycarbazole thin films (resulting from a poly(N-carbazole) (PCz) network) were prepared by electrodeposition of PVK and/or N-vinylcarbazole comonomer via precursor route and were investigated in situ by electrochemical-surface plasmon resonance spectroscopy (EC-SPS). Distinct doping-dedoping properties and morphology transitions were observed with different compositions of PVK and Cz. By electrochemical doping of the cross-linked conjugated polycarbazole units, the electrochemical equilibrium potential (E eq), which correlates to Fermi level (E f) or the work function (φ w) of the film, was adjusted in the vicinity of the anode electrode. The conjugated network PCz films were then used as a hole-injection/transport layer in a two layer device. Remarkable enhancement of PLED properties was observed when optimal electrochemical doping was done with the films. Important insight was gained on charge transport phenomena between polymer materials and conducting oxide substrates.

Electrodeposition and Thin Film Formation of Hyperbranched Poly(N-Vinylcarbazole) on Indium-Tin-Oxide Substrates

“…The large trailing peak at 310 nm is indicative of a new π to π * transition of the crosslinked carbazole moities . Our findings is also consistent with other previous works on electropolymerized PVK (Fulghum et al, 2006;Baba et al, 2004;Tria et al, 2010), which is further substantiated by the appearance of the greenish PVK film on PVK are more defined than that of linear polymer since the carbazole units present in the hyperbranched are denser and greater in number than that of their linear analogs, hence more intra -and inter-crosslinking.…”

Achieving High Efficiency of PTB7‐Based Polymer Solar Cells via Integrated Optimization of Both Anode and Cathode Interlayers

“…The electrochemical doping can regulate the electrical properities of electroactive fi lms effectively, such as WF and conductivity. [31][32][33] After moderate doping, the CMP fi lm exhibited a WF of 5.25 eV (Supporting Information, Figure S5) and a conductivity of 46 S m −1 .…”

RAFT “grafting-through” approach to surface-anchored polymers: Electrodeposition of an electroactive methacrylate monomer

“…In our group, carbazolecontaining polymers and dendrimers have been synthesized and studied [24][25][26][27][28] because of their potential applications on electroluminescent devices [29][30][31], photorefractive materials [32,33], electrochromic materials [34,35], and memory devices [36]. In all the above applications, the main use of carbazole-derivatized polymers for electro-optical function involves efficient hole transport, good solution processing properties, and high chemical stability [37][38][39][40].…”

“…In all the above applications, the main use of carbazole-derivatized polymers for electro-optical function involves efficient hole transport, good solution processing properties, and high chemical stability [37][38][39][40]. Using the precursor polymer approach, polymers with electroactive side-chain functional groups can form conjugated polymer networks (CPNs) on the electrode surface upon chemical or electrochemical oxidation processes [24][25][26][27][28]37]. The CPN formation [41,42] has also been applied to dendrimeric precursors forming shape-persistent conjugated nano-objects and electrooptically active films [43,44].…”