57‐3: Invited Paper: Solution‐Processed Electron Transporting Layer and Interface Characterization in Organic Light Emitting Diodes. Issue 1 (2nd June 2017)

• Record Type: Journal Article
• Authors: Pu, Yong-Jin; Ohisa, Satoru; Aizawa, Naoya; Chiba, Takayuki; Kido, Junji
• Is Part Of: Digest of technical papers. Volume 48:Issue 1(2017)
• Page Start: 849
• Page End: 852
• Publication Date: 2017-06-02
• Subjects: organic light emitting diodes -- solution process -- interface -- time-of-flight secondary ion mass spectrometry -- neutron reflectometry; Information display systems -- Congresses; 621.3815422
• DOI: 10.1002/sdtp.11789
• Languages: English
• ISSNs: 0097-966X

Abstract

Abstract : We demonstrate highly efficient solution‐processed multilayer OLEDs, in which hole injection layer, hole transporting layer, emitting layer (EML), and electron transporting layer (ETL), are fully solution processed. The key feature of the devices is the use of the molecular hosts in the EML, which are sufficiently resistant to the orthogonal solvents such as alcohols, used for processing upper ETLs. This allows us to construct the multilayer structure through subsequent solution‐processing steps, achieving high power efficiencies for solution‐processed green OLEDs. We also show that the composition at the resulting interface of solution‐processed layers is a critical factor in determining device performance. We perform depth‐profiling measurements of the devices by time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) and neutron reflectometry (NR). The composition at the solution‐processed EML/ETL interface is severely dependent on molecular weight of the host molecules in the EML. The mixed interface resulting from solution processing not only adversely affects the device characteristics, such as by increasing the driving voltage, but also the mixed interface beneficially affects device performance by, for example, suppressing charge accumulation at the interface. To develop highly efficient solution‐processed OLEDs, precise control of the interface structure is important.