Effect of Molecular Stacking on Exciton Diffusion in Crystalline Organic Semiconductors

Abstract

Exciton diffusion is at the heart of most organic optoelectronic devices' operation, and it is currently the most limiting factor to their achieving high efficiency. It is deeply related to molecular organization, as it depends on intermolecular distances and orbital overlap. However, there is no clear guideline for how to improve exciton diffusion with regard to molecular design and structure. Here, we use single-crystal charge-transfer interfaces to probe favorable exciton diffusion. Photoresponse measurements on interfaces between perylenediimides and rubrene show a higher photocurrent yield (+50%) and extended spectral coverage (+100 nm) when there is increased dimensionality of the percolation network and stronger orbital overlap. This is achieved by very short interstack distances in different directional axes, which favors exciton diffusion by a Dexter mechanism. Even if the core of the molecule shows strong deviation from planarity, the similar electrical resistance of the different systems, planar and nonplanar, shows that electronic transport is not compromised. These results highlight the impact of molecular organization in device performance and the necessity of optimizing it to take full advantage of the materials' properties.

Ultrasensitive organic phototransistors with multispectral response based on thin-film/single-crystal bilayer structures

“…The measurement setup used for optoelectronic characterization of the OPTs is described elsewhere. 12,23 Light at 500 nm matches the maximum absorption peak of rubrene SC in the visible range (see Fig. 1(a) and Ref.…”

Deepening Insights of Charge Transfer and Photophysics in a Novel Donor–Acceptor Cocrystal for Waveguide Couplers and Photonic Logic Computation

“…Architectures with interface between different molecular crystals receive increasing research attentions, because they exhibit unexpected properties and can be used as the prototype to study some fundamental issues . The reported Bpe‐IFB cocrystals (BICs) show a CT 1 excitonic violet‐blue PL and excellent optical waveguide property, as well as a nice spectroscopic overlap between the absorption spectrum of NTCs (Figure d), which facilitates energy transfer from BIC to NTC.…”

Preparation of Single‐Crystalline Heterojunctions for Organic Electronics

“…More impressively, these highly ordered materials have been used for varied electronic devices and fundamental research. More specifically, single‐crystalline heterojunctions prepared by lamination technique can be applied to explore the properties of metallic conduction or exciton diffusion; and those grown from epitaxial growth and solution methods are used for OFETs and OPVs. This progress will be discussed below.…”

“…The interfacial band bending lowers the necessary energy for charge generation, leading to a higher quantum efficiency. Through the photoresponse measurements, Alves's group continued to study the exciton properties of organic semiconductors . Interfaces were constructed by laminating rubrene single crystals and a variety of perylenediimide derivatives with different intra‐stack molecular distances and charge percolation networks.…”