Speaker: Antoine Kahn, Princeton University
Date & Time: January 19, 2017 2:00 - 3:00
Location: Hennings 318
Local Contact: Sarah Burke
Intended Audience: Graduate
The formidable promises of a recently “re-discovered” class of semiconductors, i.e. the organic/inorganic halide perovskites (HOIP) such as methylamonium lead tri-iodide (MAPbI3), and the rapid and steady rise in device performance achieved with these materials over the past six years, have triggered a flurry of research all over the world. This talk reviews our efforts to understand key interfaces of these materials relevant to optoelectronic devices. We report a combined electron spectroscopy-DFT study of the surface electronic structure of several compounds, e.g., MAPbI3, MAPbBr3, and CsPbBr3, which yield valence and conduction band edge positions (VBM, CBM), ionization energy and electron affinity (IE, EA), energy gap. A surprisingly low density of states is found at the VBM of these materials, with significant consequences on device physics. We report recent measurements of the electronic structure of HOIP interfaces with hole and electron transport layers used for carrier extraction/blocking in photovoltaic devices. Specifically, the role of p-doping is investigated in the case of interfaces between the HTL poly(triarylamine) (PTAA) and CsPbBr3.