11
Electronic Processes at Organic Semiconductor Heterojunctions: The Mechanism of Exciton Dissociation in Semicrystalline Solid-State Microstructures
11.1 Introduction
Unraveling primary electronic processes in polymeric semiconductors opens a fundamental window to their materials physics. The steps to generate charge by optical absorption are currently the subject of wide interest (see Ref. [1] for a comprehensive review). Here, we focus on charge generation and recombination dynamics in neat regioregular poly(3-hexylthiophene) (P3HT). This semicrystalline polymer adopts π-stacked lamellar microstructures in the solid state [2], leading to two-dimensional electronic dispersion [3]. Crystallinity induced by molecular organization results in the formation of interfaces between amorphous and crystalline domains, thus profoundly influencing the electronic properties of the material, exemplified by the high yield (
) of apparently direct charge photogeneration. Although in general 
in less organized polymeric semiconductors [4], various groups have reported up to 30% over ultrafast timescales in P3HT films at 300 K [5–9]. However, photoemission spectroscopy ...
