Photoelectrochemical / Photovoltaic system

Controlled intensity-modulated photo-spectroscopy (CIMPS) system is Zahner's flexible and high-end system for characterizing the photoelectrochemical (PEC) and/or photovoltaic systems. The CIMPS system consists of LED based light sources and has an active light feedback system, which ensures illumination of the photoelectrode/solar cell with an accurate and constant light intensity during the measurement. The feedback loop enables the use of LEDs without any warm-up time and mitigates the thermal drift effect during operation. For further information on the feedback loop and its advantages, please read the application note C in CIMPS.

 

6.1 CIMPS setup


The CIMPS system consists of a main potentiostat (ZENNIUM X or ZENNIUM Pro) and a controlled potentiostat (PP212). The ZENNIUM potentiostat is connected to the photoelectrochemical cell or solar cell under investigation and the PP212 is connected to the light source and light feedback system and actively controls the light intensity during the measurement. Fig. 1 shows the schematic of a CIMPS system.

Fig. 1: A schematic of the PP212 with the feedback loop (left) and the ZENNIUM series potentiostat with the photoelectrochemical cell (right.)


For the CIMPS system to function properly and to provide similar experimental conditions for different experiments, it is crucial that the light source, feedback sensor (photodetector) and the PEC cell/solar cell are placed every time at the same distance from each other. To ensure similar conditions for each experiment, the CIMPS system is delivered with an align bar (see Fig. 2).

 
 
Fig. 2: Proper positioning of the PECC cell, light source (Monochromatic LED), and the feedback sensor with the align bar.

 

6.2 Calibration file

 

Zahner offers two different kinds of LED-based light sources.

  • Monochromatic LEDs and
  • Tuneable light source (TLS)
 

To ensure optimum operational quality, each light source offered by Zahner is individually calibrated. Upon starting the Thales software (i.e., for IMPS/IMVS measurements, CLV or IPCE measurements), the connected light source is automatically detected by the Thales software and the correct calibration file for the light source is automatically selected. The serial number and type of the connected light source are also shown at the top of the software (see Fig. 3).
 

 
Fig. 3: The Thales software automatically detected the connected TLS03 (serial number 1029) and shows it at the top of the software. 


For old CIMPS systems, the automatic detection of light sources is not available. In such a case, the user can click on the "Calibration" icon and open the corresponding calibration file belonging to the light source. The calibration files (format: .is_) are available in the c:\THALES\CIMPS folder.

Since the monochromatic LEDs are plug & play LEDs so they can be easily replaced between two measurements and shutting down of the complete CIMPS system is not required to replace the LEDs.
 

6.3 Feedback sensors for the UV, VIS and IR range


Zahner offers monochromatic LEDs in the wavelength range from 265 nm to 1550 nm. No one photodetector can be used to optimally detect the light from such a diverse wavelength range, therefore Zahner provides 3 different sensors for use in UV (265 - 360 nm), VIS (360 - 1050 nm) and IR (900 - 1550 nm) ranges. When using different monochromatic LEDs from different light ranges, please switch to the correct feedback sensor to suit the wavelength of the light source.

 Fig. 4: Small photodiode, in the feedback loop, close to the photovoltaic cells measure the light intensity during the measurement.

 

6.4 Tuneable light source


The Tuneable light source consists of up to 29 LEDs, a white background LED, a monochromator, and a feedback sensor. The TLS is designed for the IPCE measurements and allows much higher light intensity across the wavelength range than the traditional solar simulator with a monochromator for the IPCE measurements. This high light intensity is very crucial for IPCE measurements on DSSC or organic solar cells.
 

Fig. 5: Tuneable light source for IPCE measurements.
 

In contrast to the monochromatic LEDs, the tuneable light source is kept at 1 mm distance from the solar cell or the PEC cell window. In the case of the TLS, no external feedback sensor is required (as shown in Fig. 4) as the TLS already contains a feedback sensor within its body.

TLS with PECC-2 cell:

When using a TLS with a PECC-2 cell then the illumination is possible from either window of the PECC-2 cell (electrode side or electrolyte side). For illuminating the TLS from the electrode side, the standard TLS calibration file is used (TLS calibrated for 1 mm distance). However when the TLS is placed on the electrolyte side then an additional calibration is required. In this case, the light losses from absorption in electrolyte and the reflections at the glass-electrolyte interface are taken into account and a special calibration file is prepared. In such a scenario, the proper calibration file must be chosen to ensure that the test object can be illuminated with accurate light intensity. A calibration file for the electrolyte side illumination will be named using the format 1029tls03-pecc.is_. Here 1029 is the serial number of the connected TLS03. For different users, the serial number will be different and is provided at the backside of the TLS03. The PECC in the name indicates that the calibration file is for PECC-2 electrolyte side illumination.

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