Junction Electron-Beam-Induced Current Techniques for the Analysis of Photovoltaic Devices

A number of useful electron-beam-induced current (EBIC) techniques have evolved through the study of junction behavior in photovoltaic (PV) devices in cross section as a function of light and voltage bias, temperature, and electron beam scanning parameters. The necessary hardware modifications, the techniques themselves, and their applications are presented. In the case of PV devices, light and/or voltage biasing the entire device while electron probing it in cross section permits the observation of the distribution of the narrowing or extension of the space-charge region. Monitoring the junction behavior as a function of temperature has at least two applications. In situ heating of the device in the junction EBIC (JEBIC) mode permits the observation of the rate of movement of the junction further into the material as a function of time and temperature. Through low-temperature studies of cross sections, the change in the material's electrical properties have been recorded and correlated with device I-V and quantum efficiency measurements at these temperatures. Further, the JEBIC profile has been used to predict the quantum efficiency of the device. In the case of thin-film CdS/CuinSe2 devices, newly developed JEBIC techniques have been instrumental in determining the role of oxygen in improving device performance and stability.