David M. Rampulla

Dr. Rampulla’s research focuses on the electronic and chemical properties of surfaces and interfaces relevant to solar energy conversion and storage. Surface-sensitive spectroscopic and microscopic techniques are used to gain an understanding of the fundamental electronic and chemical processes at the atomic-scale. 

The use of organic materials as the active component in photovoltaic devices is receiving increased attention due to the potential for creating a low cost solar cell. The electronic and physical structure of the interface between indium tin oxide (ITO), a commonly used transparent electrode in organic photovoltaics, and an organic semiconductor strongly affects charge-injection characteristics, which is an important factor in overall device efficiency. By studying electron conduction pathways and injection barriers of conjugated molecular wire monolayers covalently bonded to ITO, structure-function relationships can be developed to rationally design photovoltaic media based on molecular wire architectures. Techniques: inelastic electron tunneling spectroscopy (IETS), transition voltage spectroscopy (TVS), conducting probe-atomic force microscopy (CP-AFM).

The solar conversion of CO₂ emissions into methanol could mitigate global climate change, while simultaneously providing a portable fuel during times of low insolation and replacing chemical feedstock precursors, which are typically found in dwindling petroleum supplies. An investigation is underway to study the structure and composition of solar nanocatalysts and resultant reaction mechanisms on surfaces comprised of self-assembled, metal atomic chains on semiconductor substrates that combine the efficient photo-capture of a common semiconductor with the chemical reactivity of catalytic metals. Due to the nanostructured nature of the atomic chains, the surface is potentially capable of sustaining photo-generated, hot electrons and holes that can induce catalytic pathways inaccessible with thermal catalysis. Techniques: scanning tunneling microscopy (STM) and temperature programmed reaction spectroscopy (TPRS).