High Brightness Fluorescent White Polymer Light-Emitting Diodes by Promoted Hole Injection via Reduced Barrier by Interfacial Dipole Imparted from Chlorinated Indium Tin Oxide to the Hole Injection Layer PEDOT:PSS

Hong-Ren Syue; Miao-Ken Hung; Yao-Tang Chang; Ge-Wei Lin; Yu-Hsuan Lee; Show-An Chen

doi:10.1021/acsami.6b09515

High Brightness Fluorescent White Polymer Light-Emitting Diodes by Promoted Hole Injection via Reduced Barrier by Interfacial Dipole Imparted from Chlorinated Indium Tin Oxide to the Hole Injection Layer PEDOT:PSS

ACS Appl Mater Interfaces. 2017 Feb 1;9(4):3824-3830. doi: 10.1021/acsami.6b09515. Epub 2017 Jan 17.

Authors

Hong-Ren Syue¹, Miao-Ken Hung¹, Yao-Tang Chang¹, Ge-Wei Lin¹, Yu-Hsuan Lee¹, Show-An Chen¹

Affiliation

¹ Chemical Engineering Department and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing-Hua University , Hsinchu 30013, Taiwan, ROC.

PMID: 28032500
DOI: 10.1021/acsami.6b09515

Abstract

We demonstrated that introducing poly(3,4-ethylenedioxythiophene) polystyrene sulfonate as a hole transport layer (HTL) on top of chlorinated indium tin oxide (Cl-ITO) anode can lead to a deeper highest occupied molecular orbital level of the HTL (promoting from 5.22 to 5.42 eV) due to the interfacial dipole imparted by the Cl-ITO, which allows barrier-free hole injection to the emitting layer with polyspirobifluorene doped with the yellow emitter rubrene and significantly prevents excitons quenching by residual chlorine radicals on the surface of Cl-ITO. By use of poly[9,9-bis(6'-(18-crown-6)methoxy)hexyl)fluorene] chelating to potassium ion (PFCn6:K⁺) as electron injection layer and air-stable high work function (E_Φ) metal aluminum as the cathode, the performance of fluorescent white polymer light-emitting diode (WPLED) achieves the high maximum brightness (B_max) of 61 523 cd/m² and maximum luminance efficiency (η_L, _max) of 10.3 cd/A. Replacing PFCn6:K⁺/Al cathode by CsF/Al, the B_max and η_L, _max are promoted to 87 615 cd/m² (the record value in WPLED) and 11.1 cd/A, respectively.

Keywords: PEDOT:PSS; chlorinated-ITO (Cl-ITO); fluorescence; hole transport layer; interfacial dipole; polymer light-emitting diodes (PLED); polyspirobifluorene (PSBF).