Optoadmittance Spectroscopy*

Admittance spectroscopy detects and analyzes the magnitude and phase shift of electrical current in response to an applied oscillatory voltage. It is a well-known tool used to study dynamical and relaxational properties of electronic devices and materials. Here we present an extension of this technique into the optical domain. Similar to its electrical analog, a periodic voltage and DC bias is applied to a light emitting device. In addition to the current, the oscillatory modulation of the light is detected and its magnitude and phase shift are measured as a function of frequency. We show that this method is equivalent to the usual measurements of the relaxation in time-domain. The advantages of optoadmittance spectroscopy include a simple experimental setup and direct recording of the data in the frequency domain, which simplifies the analysis and often provides better resolution of the processes with different relaxation times. The analysis of both light and electrical current allows us to disentangle the relaxation processes related to the light emission from other purely electrical processes present in a device. This talk describes the experimental setup and presents the characterization of industry and research grade light emitting diodes and organic light emitting diodes.