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IMPS/IMVS to evaluate carrier transport time, recombination rates and other time scales

Intensity Modulated Photocurrent/Photovoltage Spectroscopy.

description

The IMPS/IMVS instrument allows to perform sample examination that is complementary to static photovoltage/photocurrent measurements. Monochromatic LED with modulated light intensity of sinusoidal waveform in wide range of frequencies enables to investigate many kinetic quantities: diffusion parameters, time scales of the sample: carrier transport time, recombination rates and many others. In case of photoelectrochemical samples immersed in an electrolyte, the sample may be illuminated on both sides: through the electrolyte, to investigate electrolyte-sample surface interface, or through the rear optical window for substrate-sample interface examination. The sample setup is placed in the Sample Chamber that screens ambient light and external EM fields.

Quantities measured by the instrument:

  • Minority carriers lifetime (recombination time),
  • Carrier transport time through the sample,
  • Rate of the charge transfer through the interfaces,
  • Diffusion constant,
  • Diffusion length for a given sample thickness,
  • Sample thickness for a given diffusion length,
  • Other kinetic quantities.

 

 

IMPS/IMVS modules

The instrument consists of:

Click to enlarge

specifications

 LED Revolver

  • 10 LED slots,
  • Default LED set: 365 nm, 385 nm, 405 nm, 450 nm, 520 nm, 590 nm, 630 nm, 740 nm, 840 nm, white (3000 K),
  • Custom LED selection available,
  • Typical electric power of LEDs: 3W,
  • Light intensity modulation: square, saw or sinusoidal waveform with adjustable amplitude and bias light intensity,
  • Light modulation frequency range: 1 µHz ÷ 10 kHz,

Controller

  • Maximum sampling rate: 1 kSample/s,
  • Connection with PC: via USB 2.0,

Potentiostat

  • Bias potential range: -5 V ÷ 5 V,
  • Current ranges: 10 nA, 100 nA, 1 µA, 10 µA, 100 µA, 1 mA, 10 mA,
  • Current resolution: from 1 pA to 100 nA (range dependent),

Electrochemical cuvette

  • Adapted for transparent and opaque samples,
  • PTFE container for electrolyte,
  • Reference electrode: Ag/AgCl,
  • Counter electrode: Pt.

Sample Chamber Interior

Click to enlarge

exemplary results

The measurement results shown below are obtained for nanocrystaline anatase on ITO foil in KNO3 electrolyte.

Photocurrent spectrum.

Warning: the current sign convention assumed is normal in contrast to potentiostatic measurements (adopted by all the potentiostats in the world) where the IUPAC (inverse sign) convention is used.
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Nyquist (Argand) plot in 3d showing real and imaginary part of photocurrent as a function of light modulation frequencies.
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Amplitudes of higher harmonics.
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ACCESSORIES The following accessories are compatible with the product
Light Calibrator
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