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The Root Causes of the Limited Stability of Solution‐Coated Small‐Molecule Organic Light‐Emitting Devices: Faster Host Aggregation by Exciton–Polaron Interactions
Author(s) -
Cho Yong Joo,
Zhang Yingjie,
Yu Hyeonghwa,
Aziz Hany
Publication year - 2016
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201603542
Subject(s) - materials science , oled , exciton , electroluminescence , optoelectronics , polaron , degradation (telecommunications) , vacuum deposition , coating , vacuum level , deposition (geology) , polymer , chemical physics , thin film , nanotechnology , composite material , layer (electronics) , condensed matter physics , telecommunications , paleontology , physics , quantum mechanics , sediment , computer science , biology , electron
The degradation mechanism is compared in organic light‐emitting devices (OLEDs) fabricated by solution‐coating to that in vacuum‐deposited OLEDs. Devices comprising various host materials made by vacuum‐deposition or solution‐coating are investigated. Changes in devices electroluminescence (EL) spectra during prolonged electrical driving are compared and analyzed. Hole‐only devices are also utilized, and employed to study the effects of charges and excitons, separately and combined. The results reveal that the faster degradation of solution‐processed devices relative to their vacuum‐deposited counterparts under electrical stress is due to a faster aggregation of the host materials. Interactions between excitons and polarons in the emitting layers of the devices induce this aggregation phenomenon. Although this phenomenon affects both vacuum‐deposited and solution‐coated emitting layers, it is found to occur much faster in the later. The findings shed light on the root causes of the limited stability of solution‐processed OLEDs.