Photovoltage transients

Balestra, CL, Lagowski, J., and Gatos, HC, Determination of Surface State Parameters from Surface Photovoltage Transients, Surface Science, 64, 457, 1977. 

Perhaps more challenging from both experimental and modeling perspectives is the -excitation case. Primary electron-hole pair separation occurs in the subnanosecond or picosecond time domain and light pulses with temporal resolution of 10 s (or better) are required. However, both nanosecond and picosecond light pulses have been employed [110 127] and although the analysis has been mostly confined to the slower (nanosecond) decay regime in the photocurrent (or photovoltage) transients, the rise-time domain has also been analyzed (see, e.g.. Ref. [256]). 

The photovoltaic measurements were carried out in the parallel plane capacitor arrangement. The capacitor consisted of the anodically oxidized Al+Si film on the silicon substrate, a 10 pm thick mica spacer and a semitransparent top electrode. The silicon substrate and the semitransparent electrode served as the reference and the probe electrodes, respectively. The photovoltage transients were excited with single pulses of N2 laser (wavelength 337 nm, pulse duration 10 ns, intensity 0.1 mJ/cm ) and recorded within the time range from 10 ns to about 1 ms. The excitation intensity was changed over four orders of magnitude with calibrated neutral density filters. 

Figure 2. Photovoltage transients for nanostructured silicon built-in the anodic alumina film (70 nm) at different temperatures. The shape of the laser pulse is presented for comparison.

Figure 4. Photovoltage transients in anodic alumina films of different thicknesses with built-in silicon clusters. The inset shows the thickness dependence of the photovoltag amplitude.

Mori et al. studied the transport properties of F88 polymer-templated NiO, sensitised with different dyes, including C343, also using photocurrent and photovoltage transient measurements. " Diffusion coefficients (D) were calculated from using Equation 3.45 where w is the film thickness. 

Fig. 2. Transient photovoltage across 50 Q of liana-(CH)x in the Auston switch configuration.

The transient field leads to the counter-intuitive observation that the rise time in the transient photovoltage is slower at lower injection. At very low photocarrier injection, the barrier introduced by the transient field is insufficient to block diffusive motion of carriers outside the space-charge region, so diffusive... 

Transient photovoltage decays (in both 1 M KOH and H2SO4) and electrochemical impedance spectroscopy under illumination are also indicative of better... 

We will distinguish various modes. The techniques most widely used in DSSCs are intensity modulated photocurrent spectroscopy (IMPS) which is, like IPCE, concerned with electron transport under short circuit conditions Intensity modulated photovoltage spectroscopy IMVS, which probes the competition between transport and recombination at open circuit and electrical impedance spectroscopy (EIS), which probes the bias-dependent electrical response, analogous to dark-current transients. Other variants, such as frequency-resolved transmittance, the frequency domain analogs of transient absorption, have been developed [50]. The techniques and... 

Recombination is either characterized using steady state measurements, for instance in the dark or under open-circuit conditions, or transient methods where the decay of the concentration of charges is used to analyze the strength and type of recombination. To determine the recombination rate itself is not useful because the continuity equations are solved in terms of the charge densities of electrons and holes on which the recombination rate is strongly dependent. Therefore, we need to measure directly a recombination lifetime r or an effective recombination prefactor k, which is usually defined as k = R/rP, where n is the average excess electron and hole concentration. Typically, these measurements are done by transient photovoltage measurements [31, 42, 148-152], by transient absorption measurements [148, 153] or by impedance measurements [154—156]. 

Zhu et al. have studied the effects of cations in the electrolyte on hole transport times ( ) and lifetimes (ih) in C343-sensitised NiO, prepared form Ni(OH)2 colloids, using small-modulation transient photocurrent and photovoltage measurements.Figure 3.72 shows the measured time constants plotted against /sc-... 

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