Quantum Efficiency (QE) ranks among the most fundamental techniques used to characterize solar cell performance and to determine the root cause of cell defects. The technique measures the photon to electron conversion efficiency as a function of wavelength, facilitating the study of fundamental cell parameters as diverse as front surface passivation, back surface passivation, emitter carrier lifetime, and bulk diffusion length. With the addition of voltage bias, light bias, and temperature control, an even more extensive array of cell performance parameters can be extracted, including base collection efficiency, non-ohmic contact resistance, surface and bulk trap density. QE can be applied to both conventional and emerging photovoltaics, from today’s silicon and thin film devices to emerging technologies such as dye-sensitized organic and quantum confinement devices.
FlashQE is hundreds of times faster than conventional QE systems and is revolutioning the technique.
There are two QE system technologies in the market today using incandescent lamps coupled with a monochromator or filter wheel.
Monochromator QE System:
- Strength: Resolution
- Weakness:
- Brightness
- Measurement time
- Lamp Lifetime
Filter wheel system:
- Strength: Brightness
- Weakness:
- Filter Degradation
- Time/ Measurement
- Lamp Lifetime
Due to their slow speed (~5min/spectrum), high hcomplexity, and poor reliability, conventional QE systems are used in off-line labs, monitoring roughly one out of every million cells.
With the introduction of a QE system operating at the speed of the line, this fundamental measurements of cell quality can be moved out of the lab and into the manufacturing line.
