NREL strives to provide accurate and timely measurements of electro-optical properties to help researchers and manufacturers troubleshoot problems and develop the knowledge base necessary to reduce cost, maximize efficiency, improve reliability, and enhance manufacturability.
A key issue in photovoltaics (PV) research and development is relating the performance of PV devices to the methods and materials used to produce them. Because of the nature of these devices, the electronic and optical properties of the materials are key to device performance. The relationship among materials growth and processing, the resulting electro-optical properties, and device performance can be extremely complex and difficult to determine without direct measurement of these properties.
The following table provides a condensed listing of performance applications and ranges for each electro-optical technique/capability.
Electro-Optical Characterization Techniques/Capabilities
|Typical Applications||Detection Range||Temperature Range||Non-Destructive?||Image/
|Photoluminescence spectroscopy||Determine bandgap, material quality; identify defects||0.4–2.7 µm||4–300 K||Yes||Yes|
|Minority-carrier lifetime spectroscopy||Measure minority-carrier lifetime, surface recombination; determine dominant recombination mechanisms||4–300 K||Yes||Yes|
|Optical: 0.4–>1.4 µm with 2×10-11 s resolution|
|PCD: 5×10-9 s resolution|
|Capacitance techniques||Measure carrier concentration profiles, interface state density, deep-level properties||Quasistatic to 100 MHz frequencies||77–360 K||Yes||Yes|
|Scanning defect mapping||Map dislocation and grain-boundary distributions in silicon wafers||103 to 108 defects/cm2||Room temperature||No||Yes|
|Reflectance spectroscopy||Determine numerous solar cell physical parameters, including surface roughness, film thickness, metallization properties||Reflectance to 1% accuracy from 0.4–1.1 µm||Room temperature||Yes||Yes|
|Computational Modeling||Simulate electro-optical experiments and solar cell devices through advanced multi-dimensional modeling||N/A||N/A||N/A||N/A|
Contact us for specific information about our work in electro-optical characterization.
GROUP MANAGER, SPECTROSCOPY and PHOTOSCIENCEAndrew.Ferguson@nrel.gov