Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 2: Focus Session: Structural Ordering and Electronic Transport I (jointly with CPP)

HL 2.1: Hauptvortrag

Montag, 26. März 2012, 09:30–10:00, ER 270

Neither crystalline nor amorphous: how charge transport is affected by order in organic semiconductors — •Alberto Salleo — Stanford University, Stanford, USA

From the fundamental standpoint, organic semiconductors are fascinating as they are neither crystalline nor amorphous and their microstructure plays a central role in governing charge transport. I will show that understanding disorder is the key to determining charge transport mechanism. Using advanced synchrotron-based X-ray characterization techniques we are able to define and measure structural order at different length-scales. We are particularly interested in cumulative disorder (paracrystallinity), where the lattice parameter takes on a Gaussian distribution about its mean value. The disorder parameter g allows us to rank materials quantitatively on a continuous scale, from a perfectly crystalline material (g<1%) to an amorphous one (g>10%). Using disorder as a ranking parameter, I will discuss the differences in transport between small molecule and polymer films as well as their respective inherent limitations and bottlenecks. This work may help devising design rules for new materials with desirable transport properties for polarons and excitons.