Ambient processable shallow (≤4.0 eV) and deep (≥5.8 eV) charge injection and extraction layers for high performance devices


Electrodes with sufficiently high, or low, work functions to match the appropriate band edge of the semiconductor are required in all high performance devices for efficient injection (and/or extraction) of holes, or electrons, respectively. Ambient processability will confer an added design and manufacturing advantage. In this talk, I will report our materials development to make ambient processable shallow (≤4.0 eV) and deep (≥5.8 eV) charge injection and extraction layers. For ultra-high work function interlayer, I will discuss self-compensated doped polymers which are generated by a separate charge-carrier doping of conjugated polyelectrolytes and compensation by their covalently bonded counter-ion, which enables the use of strong dopants to access extreme workfunction. This strategy also stabilize film from de-doping and suppress dopant migration. I will further discuss the role of these counter-ion and also the spectator cations in their solution-processability, bulk and interface morphologies in workfunction manipulation. For ultra-low work function interlayer, I will discuss using di- and higher-valent anions with negative gas-phase electron detachment energies, such as oxalate, sulfite, carbonate, sulfate and phosphate. Their electron donor level can remain sufficiently shallow in disordered matrices, particularly upon loss of the stabilizing hydration water, to provide spontaneous doping of the semiconductor, especially in the presence of holes injected by the opposite contact.

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