Spectroscopy photocurrent

The experimental setup and procedure is the same as that required for the basic IPCE experiments except that the requirements of electron counting are not as stringent as with IPCE, as it is not efficiency that is ultimately being reported but 

Incident Photon-to-Cuirent Efficiency and Photocurrent Spectroscopy 

Holh-Ebinger, A. Hinsch, R. Sastrawan, W. Warta and U. Wurfel, Dependence of spectral response of dye solar cells on bias illumination, in Proceedings of the 14th European Photovoltaic Solar Energy Conference and Exhibition, (2004) 

McMahon, K. Sadlon, Errors in calculated air mass 1 short-circuit currents due to nonlinear responsivities. Solar Cells 13, 99-105 (1984) 

Hohl-Ebinger, G. Siefer and W. Warta Non-linearity of solar cells in spectral response measurements, in Proceedings of the 22nd European Photovoltaic Solar Energy Conference and Exhibition, ICV.2.8 (2007) 

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Band gaps in semiconductors can be investigated by other optical methods, such as photoluminescence, cathodoluminescence, photoluminescence excitation spectroscopy, absorption, spectral ellipsometry, photocurrent spectroscopy, and resonant Raman spectroscopy. Photoluminescence and cathodoluminescence involve an emission process and hence can be used to evaluate only features near the fundamental band gap. The other methods are related to the absorption process or its derivative (resonant Raman scattering). Most of these methods require cryogenic temperatures. 

Therefore intensity-modulated photocurrent Spectroscopy has been developed by Peter and co-workers as a tool for the analysis of photocurrent responses in the frequency domain.42,43 An optoacoustic coupler is... 

Intensity-modulated photocurrent spectroscopy has been used in combination with microwave reflectivity measurements to investigate hydrogen evolution at a p-type silicon45 and an n-type silicon.46 The measurement of amplitude and phase under harmonic generation of excess carriers, performed by Otaredian47 on silicon wafers in an attempt to separate bulk and surface recombination, should also be mentioned here. 

Electrolyte contacts have been used to characterize as-deposited and annealed CdS/CdTe solar cell structures by photocurrent spectroscopy and electrolyte elec-troabsorbance/electroreflectance measurements (EEA/EER) [267-269]. 

Peter LM, Reid ID, Scharifker BR (1981) Electrochemical adsorption and phase formation on mercury in sulphide ion solutions. 1 Electroanal Chem 119 73-91 Da Silva Pereira MI, Peter LM (1982) Photocurrent spectroscopy of semiconducting anodic films on mercury. J Electroanal Chem 131 167-179... 

Duffy NW, Peter LM, Wang RL, Lane DW, Rogers KD (2000) Electrodeposition and characterisation of CdTe films for solar ceU applications. Electrochim Acta 45 3355-3365 Duffy NW, Peter LM, Wang RL (2002) Characterisation of CdS/CdTe heterojunctions by photocurrent spectroscopy and electrolyte electroreflectance/absorbance spectroscopy (EEA/EER). J Electroanal Chem 532 207-214 (see also references therein). 

Erley G, Gorer S, Penner RM (1998) Transient photocurrent spectroscopy Electrical detection of optical absorption for supported semiconductor nanocrystals in a simple device geometry. Appl Phys Lett 72 2301-2303... 

Polycrystalline thin Aims of gallium-containing CdSe, i.e., (CdGa)Se of variable composition, have been synthesized by electrochemical co-deposition and characterized by photovoltammetry, photocurrent spectroscopy, and electrochemical... 

The basic experimental arrangements for photocurrent measurements under periodic square and sinusoidal light perturbation are schematically depicted in Fig. 19. In the previous section, we have already discussed experimental results based on chopped light and lock-in detection. This approach is particularly useful for measurement at a single frequency, generally above 5 Hz. At lower frequencies the performance of lock-in amplifier and mechanical choppers diminishes considerably. For rather slow dynamics, DC photocurrent transients employing optical shutters are more advisable. On the other hand, for kinetic studies of the various reaction steps under illumination, intensity modulated photocurrent spectroscopy (IMPS) has proved to be a very powerful approach [132,133,148-156]. For IMPS, the applied potential is kept constant and the light intensity is sinusoid-... 

FIG. 19 Block diagrams for photocurrent measurements with chopped light and lock-in detection (a) as well as for intensity-modulated photocurrent spectroscopy (b). (Adapted from Ref. 85.)... 

Kokai J, Rakhshani AE (2004) Photocurrent spectroscopy of solution-grown CdS films annealed in CdCE vapour. J Phys D 37 1970-1975... 

Fig. 16 Parameters for defining the charge-transfer state energy cx in organic solar cells. Charge-transfer state energy for MDMO-PPV PCBM blend device determined by Fourier transform photocurrent spectroscopy and electroluminescence measurements. Reprinted figure with permission from [188]. Copyright 2010 by the American Physical Society...

Vanecek M, Pomba A (2002) Fourier-transform photocurrent spectroscopy of microcrystalline silicon for solar cells. Appl Phys Lett 80 719... 

Oxidation/reduction of Pb electrode has been studied using in situ spectroscopic techniques - Raman [114, 130-132], fourier transform infrared (FTIR) [133-135], Auger [136], and photocurrent spectroscopy [131, 137-141]. El-Kpsometric studies underlined nonuniform PbS04 film growth a dissolution-precipitation mechanism with nucleation and three-dimensional growth has been proposed as a result of large oversaturation of Pb(II) ionic species [142]... 

Figure 3.19 Intensity-modulated photocurrent spectroscopy, showing (a) the layout of a typical spectrometer, and (b) the response obtained AOM, acousto-optic modulator RE, reference electrode WE, working electrode CE, counter electrode FRA, frequency response analyzer...

The oxide layer of a metal such as copper may be seen as a semiconductor with a band gap, which may be measured by absorption spectroscopy or photocurrent spectroscopy and photopotential measurements. Valuable additional data are obtained by Schottky Mott plots, i.e. the C 2 E evaluation of the potential dependence of the differential capacity C. For thin anodic oxide layers usually electronic equilibrium is assumed with the same position of the Fermi level within the metal and the oxide layer. The energetic position of the Fermi level relative to the valence band (VB) or conduction band (CB) depends on the p- or n-type doping. Anodic CU2O is a p-type semiconductor with cathodic photocurrents, whereas most passive layers have n-character. 

Rakhshani AE. Study of Urbach tail, bandgap energy and grain-boundary characteristics in CdS by modulated photocurrent spectroscopy. J Phys Condens Mater 2000 12 4391 100. 

Fig. 8.7. Experimental arrangement for intensity modulated photocurrent spectroscopy (IMPS). FRA frequency response analyser. LED light emitting diode.

Current-potential measurements, in the dark and under illumination of the semiconductor working electrode, are extremely useful for first defining the charge-transfer behavior across the interface before more sophisticated experiments are undertaken. The irradiation can be either continuous or intermittent (chopped) the latter mode has the distinct advantage that both the dark and light behavior can be examined in the same scan [55, 58]. Even some dynamic information can thus be extracted under the nominally steady-state conditions typical of a cyclic or linear potential sweep experiment. Another useful steady-state experiment is photocurrent spectroscopy (performed at a fixed DC potential) [55], although this can also be dynamically performed via IMPS (see below). Such measurements not only yield the so-called photoaction spectrum of the semiconductor electrode, but also afford information on surface recombination and surface state activity at the interface as discussed below. 

G. Oskam, J. C. Schmidt, and P. C. Searson, Electrical properties of n-type (111) Si in aqueous K+FeCCNjs solution. II. Intensity modulated photocurrent spectroscopy, J. Electrochem. Soc. 143, 2538, 1996. 

J. N. Chazalviel, Photocurrent spectroscopy of interface states at a semiconductor-electrolyte junction, J. Electrochem. Soc. 127, 1822, 1980. 

L. M. Peter, A. M. Borazio, H. J. Lewerenz, and J. Stumper, Photocurrent multiplication during photodissolution of n-Si in NH4F. Deconvolution of electron injection steps by intensity modulated photocurrent spectroscopy, J. Electroanal. Chem. 290, 229, 1990. 

Investigating electron migration in nanostructured anatase Ti02 films with intensity-modulated photocurrent spectroscopy [288], it was found that, upon illumination, a fraction of the electrons accumulated in the nanostructured film is stored in deep surface states, whereas another fraction resides in the conduction band and is free to move. These data indicate that the average concentration of the excess conduction band electrons equals about one electron per nanoparticle, irrespective of the type of electrode, the film thickness, or the irradiation intensity. 

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