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Bi-layer hole-injecting layer composed of molybdenum oxide and polyelectrolyte for solution-processed OLEDs with prolonged stability

Peng, Jinghong, Xu, Xinjun, Yao, Chuang, Li, Lidong
RSC advances 2016 v.6 no.102 pp. 100312-100317
acidity, atomic absorption spectrometry, combustion, electrochemiluminescence, electrolytes, light emitting diodes, molybdenum, styrene, sulfonic acid, temperature
Currently, poly(3,4-ethylene-dioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) is predominantly used as the hole-injecting layer in solution processed organic light-emitting diodes (OLEDs). However, its strong acidity is detrimental to device stability. Here, a bi-layer hole-injecting layer (BHIL) composed of molybdenum trioxide (MoO₃) and an anionic polyelectrolyte has been used in solution processed OLEDs to replace PEDOT:PSS. The MoO₃ layer was firstly solution deposited using low temperature combustion processing, which ensured that the device had a good hole-transporting ability. Then, an anionic polyelectrolyte was deposited on to the MoO₃ layer also using a solution process, resulting in work function increase which was verified using peak force Kelvin probe force microscopy. Thus, the hole-injecting ability of the BHIL was found to be enhanced. It was found that BHIL-based OLEDs possessed a comparable electroluminescence performance but a better shelf-stability relative to the PEDOT:PSS based devices. This strategy gives a promising approach to obtaining high performance solution processed OLEDs with long-term stability.