  The investigation of paramagnetic species (such as point defects, dopants,
and impurities) in solid-state electronic devices is significant because of
their effect on device performance. Conventionally, these species are detected
and imaged using the electron spin resonance (ESR) technique. In many
instances, ESR is not sensitive enough to deal with miniature devices having
small numbers of paramagnetic species and high spatial heterogeneity. This
limitation can in principle be overcome by employing a more sensitive method
called electrically-detected magnetic resonance, which is based on measuring
the effect of paramagnetic species on the electric current of the device while
inducing electron spin-flip transitions. However, up until now, measurement of
the current of the device could not reveal the spatial heterogeneity of its
paramagnetic species. We provide here, for the first time, high resolution
microimages of paramagnetic species in operating solar cells obtained through
electrically-detected magnetic resonance. The method is based on unique
microwave pulse sequences for excitation and detection of the electrical signal
under a static magnetic field and powerful pulsed magnetic field gradients that
spatially encode the electrical current of the sample. The approach developed
here can be widely used in the nondestructive three-dimensional inspection and
characterization of paramagnetic species in a variety of electronic devices.
