The Oriel Model 70714 Light Bias Amplifier is designed for use in QE measurements of various photovoltaic cells where an external light source and/or voltage source are used to “bias” the cell under test. The Light Bias amplifier sources current to maintain a fixed voltage bias across the PV cell under test. Generally, QE testing is performed at a zero voltage DC Bias, but with a suitable external low-noise voltage source, it is possible to select a different DC voltage bias for further characterization purposes. This current has a DC component, and an AC component.

The DC component is proportional to the light bias mean Irradiance, which can be measured at the “DC Out” BNC with an external voltmeter.

The 70714 Light Bias Amplifier can provide the short circuit current (Isc) for the photovoltaic device being tested by monitoring the DC output. The Isc is obtained by dividing the voltage at this output to the resistance corresponding to DC gain. All measurements performed using this amplifier can be made in two- or four- wire configurations.
The AC component is proportional to the chopped light Irradiance from the monochromator, which can be measured at the DB9F connector with a Merlin Digital Lock-in Radiometry System.

By measuring the AC component at different wavelengths, one can construct the external and internal Quantum Efficiency curve for photovoltaic cells. The Light Bias amplifier has individual selectable gains via gain switches on the top of the amplifier for the DC and AC components.

Light biasing can be accomplished using an external light source like the 66088 QTH Illuminator using a bifurcated fiber optic deliver system for easy variable beam delivery or you can attach a77632 light guide directly to the QE system light source housing using these accessory components ( 77817 , 77357 , 71400 ). The QTH has the advantage of not introducing any source artifacts to the QE data.