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QEPVSI-B

Features

What are QE and IPCE?

External Quantum Efficiency (EQE) comparison of two samples.

Quantum efficiency (QE) – also referred to as Incident Photon to Charge Carrier Efficiency (IPCE) - indicates the ratio of the number of photons incident on a solar cell to the number of generated charge carriers. In order to understand the conversion efficiency as a function of the wavelength of light impingent on the cell, the QE/IPCE measurement is critical for materials research and cell design. With this data, the composition and topography can be modified to optimize conversion over the broadest possible range of wavelengths.

Measuring QE/IPCE

A simple, intuitive software interface is provided for configuring the instruments and scanning parameters.

The key to accurately measuring the QE/IPCE of a solar cell is to quantify the intensity of monochromatic light incident to the device under test and measuring how much current is generated. The QEPVSI-b is assembled and tested by Oriel Instruments, an industry leader in light sources and spectroscopy. Oriel provides the expertise to ensure accuracy of the system’s performance. Modulated light from a Xenon source is sent through order sorting filters and into an Oriel Cornerstone™ 260 monochromator to generate a monochromatic light output. The output beam path is then focused to a well-defined area. The monochromator scans over a user-selectable wavelength range with the output focused onto the calibrated silicon reference detector providing the radiometric measurement. A digital lock-in amplifier isolates the signal from background noise for accuracy and repeatability. This process is repeated for the cell under test. Total optical power incident on the detector is compared to the current generated by the cell under test. Instrument control, data collection and calculations are all done through Oriel’s TracQ™ Basic software.

System Components

All the items necessary for a free-space QE/IPCE system are included with the QEPVSI-b: the light source, monochromator, lock-in amplifier, software and related electronics, allowing anyone to quickly set up and run experiments. Before shipment, the QEPVSI-b is fully assembled and tested against a reference cell to ensure optimal performance.

Light Source

The system employs a 300-watt xenon arc lamp installed into an Oriel Research Housing. The lamp housing design includes a reflector behind the lamp, increasing system throughput. Its power supply ensures a stable output with very low light ripple.

Monochromator

The fully configured and calibrated Oriel Cornerstone™ monochromator provides excellent throughput to the cells under test. Ruled diffraction gratings were selected to provide high efficiency over a broad wavelength range. Micrometer driven slits allow for customization of the output beam size and resolution.

Digital Lock-in Amplifier

Ideal for sensitive optical measurements, the lock-in amplifier also controls the optical chopper and measures the silicon reference detector. The kit includes a two-aperture chopper wheel to modulate the light.

Current Pre-Amplifier

Oriel provides a current amplifier with appropriate cables to work with the digital lock-in amplifier. The amplifier has user-selectable gain and time constant settings, allowing it to be utilized with a wide variety of materials. The only item that needs to be provided is a means of connecting the sample under test to the amplifier’s BNC input connector.

Filter Wheel

A fully automated filter wheel is easily configured through the software provided with the QEPVSI-b. The appropriate order sorting filters were selected by Oriel and pre-installed for quick and easy setup.

Reference Detector

The kit includes a silicon detector with NIST-traceable spectral responsivity data characterized over its operating range. Data is provided in digital format to use with the TracQ Basic software.

Optics

From the lamp housing’s rear reflector to the collimating and focusing optics, components were selected to maximize throughput. The output beam propagates horizontally from the monochromator. Depending on the desired light path, additional accessories are available through Newport.

Opto-mechanics

An optical rail, rail carriers and positioning hardware for the reference detector and sample are provided for convenience. Additional components are available from Newport.