The pulse photoelectrical spectrometer has been developed by prof. Konrad Szacilowski from AGH University of Science and Technology and then designed and built by Instytut Fotonowy. It serves as a scientific tool to automatically characterize photoelectrical properties (photocurrent, photovoltage) of wide band gap semiconductors illuminated by relatively strong light in UV, VIS and NIR ranges as a function of incident light wavelength.
To approximate solar light for many applications we offer Air Mass Filters. These filters modify the spectral output of the arc lamp to mimic natural solar conditions.
Advanced software of the spectrometer allows for straightforward recording of photocurrent action spectra, photovoltage action spectra along with potentiodynamic and galvanodynamic measurements at constant wavelenght both in CW and pulsed mode. It also provides Incident Photon to Converted Electron (IPCE) ratio as a function of wavelength and bias potential.
Furthermore, the device can be coupled with other detectors, including Kelvin probes, conductivity probes, etc. The devices’ controller takes care of emitted light wavelength, exposition times, proper light edge filters handling and synchronization with a potentiostat.
The monochromator is equipped with two switchable gratings to uniformly cover a wide light spectrum. The light power exceeds 10 mW/cm2) in most of the spectral range.
The spectrometer is ready to be connected with peripherial devices like potentiostats, Kelvin probes, synchronous light choppers for lock-in amplified measurements, rotating disk electrodes, electromagnetic valves, LED illuminators, magnetic stirrers, automatic pipettes, temperature controllers, etc.
Many of those peripherials, potentiostats included, can be directly ordered from Instytut Fotonowy.
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The parameters shown beneath are typical for the devices produced so far. All of them can be tailored to specific requirements if necessary.
The spectrometer can be used for automatic measurements and visualization of obtained results. Here is the typical photocurrent action spectra for nanocrystalline TiO2 (EVONIK Aeroxide P25) at ITO@PET photoelectrode in 0.1 M KNO3 depicted as a 3D photoactivity map.
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Figure bellow “… shows the photocurrent intensity as a function of the electrode potential under pulsed illumination at 450 nm. BiOI clearly exhibits the Photoelectrochemical Photocurrent Switching Effect (so called the PEPS effect). It was described for the first time by Szaciłowski et al. in 2006 [22-25]. This phenomenon is observed on semiconducting electrodes and is defined as a change in a photocurrent direction (i.e. anodic-to-cathodic transition or vice versa) due to changes of the electrode potential or wavelength of incident light. Such a behavior is very interesting from the point of view of nano- and molecular electronics. When an incident photon is treated as a bit of information and potential of the electrode controls the work of the device, such a system may process information as a logic gate or 1:2 demultiplexer [26-28]. Thus, BiOI may be a promising compound for information processing at the nanoscale. Photocurrent switching potential is equal to 0.5 V vs. NHE in air. For more positive potential values the anodic photocurrent is observed, the more positive potential, the higher intensity of the generated current. For more negative potentials than the switching point, cathodic photocurrent is observed only in the presence of oxygen. Analysis of the shape of a photocurrent pulse (the inset in Fig. 4) may provide some information about recombination processes. The regular, rectangular shape of the photocurrent profile indicates, that a steady state on the photoelectrode under illumination occurs i.e. photogenerated charge carriers are efficiently collected by the conductive support and the recombination processes are insignificant as well as other side processes (e.g. surface charging due to high impedance of the semiconductor/conductor interface). In order to explain the PEPS phenomenon observed on the BiOI electrode, pulsed photocurrent spectroscopy was employed. This technique enable to determine how the photocurrent depends on the wavelength of incident light and the electrode potential. “
Linear sweep voltammetry of BiOI electrode under pulsed illumination at 450 nm, scan rate 5 mV/s, 0.1 M KNO3 10 mM KI, scan in the air and under nitrogen. The inset shows the kinetics of photocurrent evolution under constant potential at 450 nm. Red line represents anodic photocurrent at 0.9 V vs. NHE, blue – cathodic photocurrent at 0.2 V vs. NHE.click the photo to enlarge
Photocurrent amplitude as a function of incident light wavelength and photoelectrode potential in oxygenated electrolyte containing 10 mM KI.
P. Kwolek and K. Szaciłowski, “Photoelectrochemistry of n-type bismuth oxyiodide”, Electrochimica Acta 104 (2013), 448-453click the photo to enlarge