Voltage-response time curves

Results for a 20 pm thick sample of polycarbonate containing 50 mass% TPD for a field of 1.5 x 107Vm-1 at 296 K with charges injected from an indium tin oxide (ITO) electrode coated with a 0.1 pm thick layer of PPV are shown in Fig. 8.30(b). The limiting current is close to the trap-free SCLC, indicating that the PPV-coated ITO acts as an efficient hole-injecting electrode. The lower curve is the TOF transient recorded under identical conditions. The arrow on the lower curve indicates the transit time and that on the upper curve is 0.8 of this value. The step-voltage response is therefore close to the theoretical prediction. 

Many times, in an effort to reduce amplifier noise, capacitors are added across the output of the amplifier, and occasionally at the input (45). These capacitors frequently reduce the response time of the amplifier, which causes a shift in the curve peaks and also a loss of peak resolution. A proper value of capacitor must be used, if noise is a problem, to form a compromise between noise reduction and loss of peak resolution. Amplifier impedance mismatch can also cause nonlinear output voltages, which can distort the curve peaks. 

The viscoelastic properties of liquid crystals are very important, and mainly determine the behavior of liquid crystals in external electric fields, defining such characteristics as controlling voltages, steepness of the transmission-voltage curve, response times, etc. Now only the phenomenological theory of the viscoelastic properties of nematic liquid crystals is essentially complete [18, 28]. 

The voltage sweep and current response for this experiment are shown in Figure 2-7. The data can be represented as a current-time curve, or, since the potential is linearly related to time for each half-cycle, as a current-potential curve (the usual representation). Note that reduction current is taken as positive, the cathodic sweep goes from left to right. For any CV, the direction of the initial sweep should be indicated or at least apparent (the initial sweep potential is always set, if possible, at a potential where zero faradaic current occurs). 

The response time, t , is defined as the time taken by the measuring assembly to reach a given percentage a of the final cell voltage following a given change in activity or by the slope AElAt of the dynamic response curve. For a detailed discussion of the dynamics of ISEs, see Ref [99],... 

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