Developing and applying the scanning probe microscopy technique for solar cell materials

Abstract

The study of electrical properties of solar cells at the nanometer (nm) scale has benefited greatly from characterization techniques using scanning probe microscopy (SPM), a unique and powerful tool. These characterization techniques help scientists understand the fundamental physics of materials properties and device operation and provide vital information in photovoltaic research. This work focuses on developing and applying SPM, which includes atomic force microscopy (AFM) and scanning electron microscopy (SEM)-based characterizations, to solar cell materials and devices. We include extensive studies of current and emerging photovoltaic materials and devices, such as silicon, copper indium gallium diselenide (CIGS), copper zinc tin diselenide (CZTS), III-V, and perovskite materials and devices. The subjects covered in my research concern the following: 1) understanding fundamental physics of device operation of CIGS and CZTS solar cells, and the nature of their p-n junction; 2) developing an in-situ characterization capability on an AFM platform to study photovoltaic reliability; 3) studying the fundamental mechanism of potential-induced degradation; 4) developing the near-field transport imaging (TI) technique, combining SEM and near-field optical microscopy primarily to study defects associatedvwith carrier transport; 5) applyingvTI on GaAs hillock defects to investigate how hillock defects affect carrier transport; 6) investigating the electron-beam-induced damage on novel perovskite materials; and 7) using Kelvin probe force microscopy (KPFM) to examine the p-n junction quality of SnO2-based solar cells.