QUESA is suitable for measuring the quantum efficiency of PV solar cells and photo-dectors.
This product is based on discrete wavelengths emitted by LEDs. The LEDs are gaining more and more attention and applied in many technics as a replacement of traditional lamps or as a direct monochromator sources. The particular property of spectral distribution of the LED which is a quasi Gaussian leads to a direct deduction of spectral response measured at the central wavelength of the LED emission spectrum. Indeed the measured current on a photovoltaic cell illuminated by a monchromatic LED is directly proportinal to the spectral response at the center of emission of the LED spectrum and to the power of the LED light. This behaviour has been validated by experiment and calculation. Therefore, by using enough LED sources (>31 wavelengths), one can scan the whole visible and NIR solar spectrum (370-1200 nm) to get an EQE of a solar cell. Hence the spacing of each measured point is typically 10 to 25 nm which is largely enough to plot an EQE of all types of solar cells. The number of wavelengths can be customised and increased because the sytem is scalable. This method has a significant advantage on conventional dispersive method (Monochromator) since the illumination intensity for each wavelength is much more important. This leads to a simplification of the equipement in Optics and Electronics (no need of complex electronics to measure very small signal such as Lock-In-Amplifier and this implies a high signal to noise ratio (SNR). The absolute EQE measurements performances are similar to the conventional Lamp/monochromator based EQE system (see figure below). The method and system are compliant with the norm ASTM E1021-15 related to measurement of spectral responsivity of a photovoltaic device.
It has additionally the following advantages compared to conventional Lamp/monochromator products:
- Fast measurement: < 30s
- Very stable and reproducible measurements
- High flexibility and scalability
- very compact and suitable for Glove-Box applications
- No optical adjustment needed
The QUESA-1200 has the following main characteristics:
EQE and SR option:
- The standard measurements of EQE and Spectral Response (SR) over the range from 375 nm to 1200 nm with up to 32 wavelengths. Extension of wavelength range is an option.
- The number of wavelength and spacing can be customised: the lower limit of sapcing is 5 nm and the upper limit of wavelength number is 64. Please contact us if you have a special request.
- Jsc (mA/cm²) is deduced by integrating the SR over the AM1.5G solar spectrum
- Reproducibility of EQE < +/- 1%
- Stability of measurement < 2% when room temperature is stable (within variation of less than 2°C), otherwise a quick calibration with reference cell can be performed if necessary
- Bias light selectable with software only: no hardware change
- Bias light selectable over the range of 375 nm to 1200 nm. A bias-light spectrum file can be created and stored in library
- The EQE can be measured with white bias light
- Double junction can be measured by selecting the desired bias light spectrum file
- Electrical bias option: +/- 5 V
- The illumination diameter can be adjsuted from 1 mm to 10 mm
- The basic option is for superstrate-type solar cells: illumination is from bottom to top and the electrical contacts or from the top
- additional kit can be supplied for samples with substrate-type configuration: illumination are on the same side as electrical contacts: from top to bottom.
- Light and measurement can be performed in AC or DC or both DC and AC modes
- Data are stored in excel-type format: EQE, SR and Jsc and acquisition parameters
- Tempertaure reading of sample stage
- Other options on request
Solar simulator option:
- I(V) option can be used by activating all the LEDs or parts of LEDs depending on the desired spectrum. The illumination intensity up to 1 Sun for the working spectrum range of 375-1200 nm.
- The spectrum can be adjusted to AM1.5G class B type
- The spectrum can be adjusted to AM1.5G class A according to IEC norms
- The I-V works in Flash mode with adjustable pulse width and time between pulses
- FF, Voc and Jsc and Rs and Rsh and hence solar cell efficiency can be deduced from I(V) measurements.
- different illumination sizes can be obtained: please ask us for more details
The equipment size is 40x20x30 cm (LxWxH): very compact
The system can be inserted in Glovebox with only one USB cable connection. No heating from the system since the light source is OFF in standby mode.