title: High resolution in-operando microimaging of solar cells with pulsed electrically-detected magnetic resonance.
abstract: The in-operando detection and high resolution spatial imaging of paramagnetic defects, impurities, and states becomes increasingly important for understanding loss mechanisms in solid-state electronic devices. Electron spin resonance (ESR), commonly employed for observing these species, cannot meet this challenge since it suffers from limited sensitivity and spatial resolution. An alternative and much more sensitive method, called electrically-detected magnetic resonance (EDMR), detects the species through their magnetic fingerprint, which can be traced in the device's electrical current. However, until now it could not obtain high resolution images in operating electronic devices. In this work, the first spatially-resolved electrically-detected magnetic resonance images (EDMRI) of paramagnetic states in an operating real-world electronic device are provided. The presented method is based on a novel microwave pulse sequence allowing for the coherent electrical detection of spin echoes in combination with powerful pulsed magnetic-field gradients. The applicability of the method is demonstrated on a device-grade 1-μm-thick amorphous silicon (a-Si:H) solar cell and an identical device that was degraded locally by an electron beam. The degraded areas with increased concentrations of paramagnetic defects lead to a local increase in recombination that is mapped by EDMRI with ∼20-μm-scale pixel resolution. The novel approach presented here can be widely used in the nondestructive in-operando three-dimensional characterization of solid-state electronic devices with a resolution potential of less than 100 nm.
authors.affiliation: Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Itai
authors.initials: I
authors.lastname: Katz
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie, Institut für Silizium-Photovoltaik and Berlin Joint EPR Laboratory (BeJEL), Kekuléstr. 5, D-12489 Berlin, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Fehr
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie, Institut für Silizium-Photovoltaik and Berlin Joint EPR Laboratory (BeJEL), Kekuléstr. 5, D-12489 Berlin, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Schnegg
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie, Institut für Silizium-Photovoltaik and Berlin Joint EPR Laboratory (BeJEL), Kekuléstr. 5, D-12489 Berlin, Germany. Electronic address: lips@helmholtz-berlin.de.
authors.forename: Klaus
authors.initials: K
authors.lastname: Lips
authors.affiliation: Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Haifa 32000, Israel. Electronic address: ab359@tx.technion.ac.il.
authors.forename: Aharon
authors.initials: A
authors.lastname: Blank
keywords: EPR; ESR; Electrically-detected magnetic resonance; Semiconductor defects