Optoelectronic measurements by Fourier transform

We have developed a simple measurement system adaptable to a Fourier Transform Spectrometer (FTIR) to perform optoelectronic measurements on semiconductors or solar energy conversion devices. The system allows Fourier Transform Photocurrent Spectroscopy (FTPS), transmission-reflection, and spectral response measurements on solar cells.

The advantages of a system based on data acquisition and processing by Fourier transform, compared to 'classical' systems using a monochromator, are the speed of acquisition of a spectrum, a few tens of seconds, and the resolution of the acquisition, of the order of, or even less than, a nanometre. The speed of the measurements allows spectral response mapping on large solar cells.

The figure below shows a schematic of the system developed at GeePs [1]. A double optical fibre is used to collect the light from the Michelson interferometer on one of its branches. The light coming out of the fibre is sent to the sample to be studied, which can then be placed in a cryostat under vacuum. The second branch of the fibre can be used to make reflection measurements or to superimpose an optical bias as in the case of studying the spectral response of multi-junction cells. In all cases, the response signal from the sample is then amplified and processed by the FTIR to give the final spectrum.

The addition of blue and UV LEDs to the halogen light source at the entrance to the Michelson interferometer, coupled with calibrated c-Si and c-Ge detectors, allows us to cover a wavelength range from 350 to 1800 nm. 

Diagram of the opto-electronic measurement system using FTIR.

Références

[1] N. Puspitosari, C. Longeaud, Rev. Sci. Instrum. 88, 086112 (2017). http://dx.doi.org/10.1063/1.5000057

This measurement system was developed with the financial support of the Institut Photovoltaïque d'Ile de France (IPVF, Palaiseau, France).

Contact : longeaud@geeps.centralesupelec.fr