PV >Applications >Quantum Efficiency

Quantum Efficiency

One of the most important parameters of a solar cell is its efficiecy.  Two measures of efficiency are Internal Quantum Efficiency (IQE), defined as the electrical current produced per photon entering the Quantum Efficiency (QE), defined as the electrical current produced per photon incident on the cell.  The difference, obviously, is the reflected light.

The efficiency of any solar cell varies spacially within the cell and may vary with the wavelength of the incident light.  A region of poor efficiency has a disproportionate effect on reducing the efficiency of the overall cell, so it is beneficial to study areas of low efficiency and reduce them as much as possible. 

Sunlight includes a broad spectrum of light, so it is desirable if the solar cell converts as much of the incident spectrum to electricity as possible.  Low efficiency caused by poor response to some wavelengths and not others is usually caused by the anti-reflective coating.

Semilab systems measure quantum efficiency by measuring the reflectance at 4 discrete wavelengths and by measuring the Light Beam Induced Current (LBIC) at each wavelength.  The WT-2000PV creates high resolution maps of QE, IQE, LBIC, and reflectance of solar cells.