Tum-on voltage

Parker observed that the tum-on voltages for devices with different thicknesses of the semiconducting polymer layer are roughly the same and equal to the voltage required to reach the flat-band condition [22]. As shown in Fig. 4.9, however,... 

Suzuki and co-workers [14,15] fabricated P-SiC p-n junction diodes using a mesa structure. The tum-on voltage at room temperature was 1.2 V and a reverse leakage current of 5 pA was measured at - 5 V. This leakage current is much greater than that for a-SiC diodes. Both parameters were severely degraded at elevated temperatures. Edmond et al [16] and Avila et al [17] have also produced p-n junction diodes in P-SiC. These diodes were made by ion implantation and operated up to 673 K. 

In a typical voltammetric experiment, the applied voltage (V) is ramped at a constant rate, dV/dt, and the resulting transient current response is acquired. In general, the measured cmrent has two components a conductive component that persists with a constant bias, and a capacitive component that is proportional to the sweep rate (dV/dt) and the capacitance (C). The conductive component is normally negligible below the tum-on voltage of an OLED... 

MEH-PPV clay hybrid nanocomposite materials prepared by in situ polymerization in organically modified montmorillonite show a comparatively higher current and a lower tum-on voltage. By controlling the ratio of monomeric precursors to montmorillonite, exfoliated nanocomposites can be obtained. In intercalated structures, the polymer chains are merely inserted into the interlayer spaces of the montmorillonite. However, in the exfoliated structure, two-dimensional nanospaces will no longer be present. 

As can be seen from the typical luminance-voltage characteristic presented in Fig. 6.6, light generation requires a minimum voltage, the tum-on voltage, at which light emission commences. 

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