Electronic Processes at Organic Semiconductor Heterojunctions: The Mechanism of Exciton Dissociation in Semicrystalline Solid-State Microstructures

Francis Paquin, Gianluca Latini, Maciej Sakowicz, Paul-Ludovic Karsenti, Linjun Wang, David Beljonne, Natalie Stingelin, and Carlos Silva

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 (img) of apparently direct charge photogeneration. Although in general img 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 ...

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