SEM (Scanning Electron Microscopy)
XRD (X-Ray Diffraction)
AFM (Atomic Force Microscopy)
Measuring the Internal Quantum Efficiency (IQE) of a solar cell tells us how many electron-hole pairs are collected by the device for every photon of light that actually penetrates the solar cell. The measurement is done over a range of wavelengths of light, typically 300 to 1000 nanometers. IQE tells us how efficient each of the various sections/layers of the solar cell are at changing light into electricity.
Light from 500 to 1000 watt halogen lamp is made to be incident on a monochromator, which only allows light of a particular wavelength through (monochromatic light). That light is focused on the solar cell and its photocurrent is measured, and the reflected light is measured using a calibrated detector. The number of photons incident is also observed at each wavelength so that a total of three measurements are done. IQE is then computed using the following equation:
The IQE measurements we do in room 306B of the Engineering Building give us great feedback on our fabrication processes, making it a very valuable characterization tool for solar cells.
Electronic Devices Laboratories:
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