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We present a compact model for polymer thin film transistors (TFTs) operating in forward subthreshold region. Due to the threshold voltage shift in these devices, the bias point of a device operating for a sufficiently long time moves toward the subthreshold region. Therefore, modeling subthreshold operation in polymer semiconductor based TFTs is important. We particularly address two areas where polymer TFTs are different from other disordered materials such as amorphous silicon. Firstly, the shape of the density of deep states cannot be assumed to be purely exponential. Such an assumption does not provide fine modeling of the subthreshold slope. Secondly, for subthreshold operation particularly under high drain-source bias, we need to include Poole–Frenkel type transport mechanisms such as variable range hopping and space charge limited current. This paper includes these features and develops a compact closed form model. [ABSTRACT FROM AUTHOR]

The electron-injection capability of solution-processed cesium stearate films in organic light-emitting diodes is investigated. Cesium stearate, which is expected to exhibit good solubility and film formation due to its long hydrocarbon chain, is synthesized using a straightforward procedure. Light-emitting diodes are fabricated using orange-, yellow-, and blue-emitting conjugated polymers, comprising a cesium stearate electron-injection layer deposited from ethanol solution. It is demonstrated that these devices perform as well as benchmark devices using vacuum-deposited barium as electron-injection layer, without loss of color purity. [ABSTRACT FROM AUTHOR]

The interpretation of electron currents in conjugated polymers is strongly hindered by the occurrence of hysteresis. We investigate the transport of electrons in electron-only devices based on derivatives of poly(p-phenylene vinylene) (PPV) for various hole-blocking bottom electrodes as well as purification of the polymer. The use of a variety of hole blocking bottom contacts, as metallic electrodes and n-type doped polymers, did not give any improvement in the observed hysteresis. By purification of the PPV, hysteresis free electron-only currents can be obtained. The deep traps responsible for hysteresis, with a concentration in the 1016 cm-3 range, are not responsible for the trap-limited electron transport as observed in purified PPV. [ABSTRACT FROM AUTHOR]