Improved electron injection in polymer light-emitting diodes using anionic conjugated polyelectrolyte

Abstract

We report improved performance in polymer light-emitting diodes incorporating conjugated polyelectrolytes as an electron injection layer (EIL). When we introduce water soluble conjugated polymers, poly[9,9′-bis(4-sulfonatobutyl)fluorene-co-alt-1,4-phenylene] (anionic PFP), between the aluminum (Al) cathode and emissive layer, the devices show an increased electroluminescence efficiency with a lowered turn-on voltage. We believe the mobile Na+ ions in the EIL layer directly influences the device efficiency by forming a low work function layer at the interface between the EIL and Al cathode, thereby facilitating the electron injection into the emissive layer.

Conjugated zwitterionic polyelectrolyte-based interface modification materials for high performance polymer optoelectronic devices

“…Moreover, solution-processed multilayer devices, which are critical for a better device performance, can be easily realized by depositing different layers with orthogonal solvents. For examples, many types of highly polar pendant groups (such as cationic, 8,14,42,43 anionic, 44,45 zwitterionic 34,46,47 and neutral highly polar pendant groups 14,18,32,[48][49][50][51][52] ) and conjugated main chain building blocks (such as uorene, 8,14,18,34,[42][43][44][45][46][47][48][49][50][51] carbazole, 30,52 triphenylamine, 32,53,54 thiophene 23,27,33 etc.) 3,5,[14][15][16] In polymer light-emitting diodes (PLEDs), WSCPs can greatly enhance the electron injection from high work-function metal cathodes, which in turn leads to the realization of high-efficiency all-printable PLEDs.…”

“…17 Aerwards, it was demonstrated that WSCPs also worked well as interlayers in polymer solar cells (PSCs). For example, WSCPs with electron-rich main chains (such as polyuorene, 8,14,18,34,[42][43][44][45][46][47][48][49][50][51] polycarbazole 30,52 and polythiophene 23,27,33 ), which have been previously considered as typical p-type semiconductors, behaved very well as interface modication layers for cathodes in PLEDs and for electroncollecting electrodes in PSCs. [39][40][41] For their versatile applications in optoelectronic devices, many efforts have been paid to the development of new WSCPs interlayer materials.…”

Hybrid organic-inorganic light-emitting electrochemical cells using fluorescent polymer and ionic liquid blend as an active layer

“…Therefore, the HyPLECs exhibit extremely low turn-on, and high luminance efficiency at low operating voltage without matching the work functions between each electrode and active layer. 23,24 The device performances of FTO/ZnO/SY:ILMs blend/Au device with different ILMs content and FTO/ SY:ILMs blend ͑25 wt %͒/Au device are presented in Fig. 2.…”

The dynamic organic p–n junction

“…[14][15][16][17][18][19][20][21][22] The nominal difference between an LEC and an OLED is that the former contains mobile ions in the active material. [23][24][25][26][27][28][29][30] These ions rearrange during operation, which in turn allows for a range of attractive device properties, including low-voltage operation with thick active layers and stable electrode materials. [31][32][33][34][35][36] However, the further development of LECs is currently hampered by an inadequate understanding of the device operation.…”