Intensity modulated photocurrents on an anodically oxidized lead electrode in sulfuric acid solution

Effect of Aging and PCBM Content on Bulk Heterojunction Organic Solar Cells Studied by Intensity Modulated Photocurrent Spectroscopy

“…In the Bode representation, the imaginary component of the ac photocurrent for the encapsulated cell (curve 1) remains negative at all modulation frequencies, whereas the imaginary components for nonencapsulated cells (curves 2 and 3) change the sign and become positive at lower frequencies (photocurrent leads the light intensity). Such arcs as well as corresponding positive phase shifts are typical manifestations of the occurrence of interfacial recombination. ,− All nonencapsulated cells demonstrated such arcs in our measurements, whereas all encapsulated cells lacked this feature. Therefore, we must draw a very important conclusion that encapsulation appeared to be a very effective measure to prevent the occurrence of interfacial recombination in bulk heterojunction devices.…”

Intensity modulated photocurrent spectroscopy (IMPS) of solid-state polybithiophene-based solar cells

“…Two main mechanisms of the IMPS response have been considered in the literature: the relaxation of photogenerated carriers on discrete or distributed surface states [6,[29][30][31][32], and slow transport of photogenerated carriers to the interface with or without trapping and bulk recombination [7,8,[33][34][35]. In the first mechanism, the photogenerated carriers are rapidly transported to the interface and charge it.…”

Suppression of Surface Recombination on TiO2 Anatase Photocatalysts in Aqueous Solutions Containing Alcohol

“…From the form and parameters of the frequency dependence of modulated photocurrents, one can derive important information on the kinetics of surface processes that occur at semiconductor electrodes. Further details regarding the IMPS technique and the principles of the frequency spectra analysis can be found elsewhere. ,, Here we note only that the IMPS technique allows easy determination of the rate of the surface recombination process 17,18,20,21,23 as well as detection of the photocurrent multiplication mechanism. ,,,, When the surface recombination is the dominant process, the amplitude of the ac photocurrent is dependent on the light modulation frequency and increases from zero to some limiting value g , which is called the generation current and is determined chiefly by the magnitude of the band bending. Alternatively, when the dominant process is the charge transfer to the species in the solution, as is the case at high values of band bending, no frequency dependence (photocurrent relaxation) is observed.…”

“…This mechanism is the one that is usually observed with semiconductor electrodes at low band bending. However, in some cases this mechanism can be complicated by follow-up electrochemical reactions, ,,, diffusion of reacting species, or photocurrent relaxation occurring at several types of surface states . Also, we should note additional high-frequency photocurrent relaxation that is due to uncompensated IR drop between the electrode and the tip of the Luggin capillary and is known as “cell effect” .…”

“…An efficient means for detailed examination of the mechanism of photoelectrochemical decomposition of organic compounds on semiconductor electrodes and, in particular, for direct demonstration of the effect of organic additives on the surface recombination rate and/or occurrence of the photocurrent doubling mechanism is to use intensity-modulated photocurrent spectroscopy (IMPS). The IMPS technique, which is also referred to as optoelectrochemical impedance, has proven to be a powerful tool for studying the kinetics of photoelectrochemical processes at semiconductor electrodes 14,[16][17][18][19][20][21][22] including TiO 2 electrodes, 23,24 but, until recently, there has been no attempts to apply this technique to the studies of photodecomposition of organic compounds on such electrodes. Only lately two papers 12,13 were published that presented the results of IMPS measurements on single-crystal TiO 2 (rutile) and ZnO electrodes in the presence of organic compounds.…”