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Persistent photoconductivity (PPC) behavior in organic phototransistors has fascinating potentials in applications of photoelectronic devices. A key issue is how the presence of air affects the PPC behavior. Here, combining with the theoretical and experimental results, the PPC behavior is associated with photogenerated electrons trapped in oxygen atom-induced the reduced Lowest Unoccupied Molecular Orbitals or oxygen molecule-induced new trap state within energy bandgap of organic semiconductor. Inspired by the potential applications arising from the PPC behavior, organic memory phototransistors (OMPTs) are achieved by light programming and electrical erasing. The OMPTs show bistable current states as well as long retention times. Our results suggested that oxygen in air plays a key role in PPC behavior and provides a guidance for controlling the PPC behavior toward integrated multifunctional optoelectronic devices. [Display omitted] • 2DMCs are used as OSCs layer to rule out the influence of grain boundaries on OPTs. • PPC behavior can be obtained when OPTs measured in air compared with OPTs measured under vacuum. • Oxygen-induced trap states play a critical role in PPC behavior. • Memory characteristics arising from PPC behavior are investigated. [ABSTRACT FROM AUTHOR]

Abstract: We report a method for inkjet-printing an organic semiconductor layer on top of the electrolyte insulator layer in polyelectrolyte-gated OFETs by using a surface modification treatment to overcome the underlying wettability problem at this interface. The method includes depositing an amphiphilic diblock copolymer (P3HT-b-PDMAEMA). This material is designed to have one set of blocks that mimics the hydrophobic properties of the semiconductor (poly(3-hexylthiophene) or P3HT), while the other set of blocks include polar components that improve adhesion to the polyelectrolyte insulator. Contact angle measurements, atomic force microscopy, and X-ray photoelectron spectroscopy confirm formation of the desired surface modification film. Successful inkjet printing of a smooth semiconductor layer allows us to manufacture complete transistor structures that exhibit low-voltage operation in the range of 1V. [Copyright &y& Elsevier]

Abstract: Substantial potential steps ∼0.5eV are frequently observed in organic multilayers of donor and acceptor molecules. Often such potential steps depend on the order in which the individual layers are deposited, or on which substrate they are deposited. In this paper we outline a model for these potential steps, based upon integer charge transfer between donors and acceptors, charge equilibration across the multilayer, and simple electrostatics. Each donor, acceptor, or substrate material is characterized by a pinning level, and the potential profile can be deduced from the sequential order of the layers, and the differences between their pinning levels. For particular orderings we predict that intrinsic potential differences lead to electric fields across individual layers, which may falsely be interpreted as band bending. [Copyright &y& Elsevier]