Current Research - Molecular Electronics

 

 

Photoisomerization Dynamics in Photochromic Molecules

A trend known as Moore’s first law states that, by shrinking their size, the number of transistors on computer chips will double every 18 months. These advances however come at the expense of exponential increase in cost for new chip-fabrication plants (Moore’s second law). Molecular scale electronics (MSE) has the potential to go much smaller. Most importantly, as molecular electronics relies on self-assembly rather than lithography it can beat Moore’s second law. Consequently, the molecular way of thinking will become increasingly profitable as the size of electronic devices continues to shrink.

Photochromic molecules undergo reversible structural changes upon light-activation and thus show a potential for use as building blocks in active molecular scale devices. Fundamental requirements for application of photochromatic system to photonic devices include high efficiency, fast response to an external stimulus, and a long lifetime. While many molecules can offer ultrafast response times, multiple relaxation pathways can lead to inefficient switching or photochemical reactions resulting in destruction of the molecular device. As the quantum yield of the desired outcome is governed by the competition between different pathways only by speeding up the desired process (e.g. ultrafast switching) it can beat out all dissipative processes. The rational design of active molecular devices thus requires a thorough understanding of electronic relaxation dynamics of its building blocks. We use time-resolved photoelectron spectroscopy combined with optical and chemical techniques to characterize and ultimately control photoisomerization dynamics in photochromic molecules.

 

Department of Physics and Astronomy

Ullrich Group