Microwave Instrumentation and Sensing Techniques for Quantum Efficiency and Minority-Carrier Lifetime Measurements

• Main Author: Lu, Kyle Benjamin
• Format: Others
• Published: PDXScholar 2017
• Subjects: Microwave measurements; Solar cells; Electrical and Computer Engineering
• Online Access: https://pdxscholar.library.pdx.edu/open_access_etds/3503; https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=4512&context=open_access_etds

A non-contact method characterizing the quantum efficiency of a solar cell using the microwave reflectance signature is presented in this thesis. Traditional solar cell quantum efficiency (QE) measurements are only possible near the completion of the fabrication process using contacts in direct physical connection with the metalized surface tabs to probe and extract charge carriers from the device. However, pressure within the solar metrology industry to report the spectral performance of the device earlier in the manufacturing process as part of the process control loop requires that a new non-contact method be developed. This thesis work contributes the development of a non-contact focused microwave reflectance technique capable of acquiring the full 365nm - 1100nm spectrum in under 1 minute. Unlike many similar Time Resolved Microwave Conductivity (TRMC) and Microwave Photoconductivity Decay (µPCD) systems based on the open-ended waveguide technique, this measurement is developed to perform measurements in the far-field. As such, a different mechanism for understanding the problem is presented using the modulated scatterer concept from antenna theory. Using a combination of high dielectric sensor pads and negative-index of refraction microwave lenses, we are able to tune the far-field field probe size from 5mm-150mm allowing for high speed single point in-line measurements or high spatial sensitivity laboratory measurements.