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Interplay of structural dynamics and electronic effects in an engineered assembly of pentacene in a metal–organic framework

Charge carrier mobility is an important figure of merit to evaluate organic semiconductor (OSC) materials. In aggregated OSCs, this quantity is determined by inter-chromophoric electronic and vibrational coupling. These key parameters sensitively depend on structural properties, including the densit...

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Detalles Bibliográficos
Autores principales: Haldar, Ritesh, Kozlowska, Mariana, Ganschow, Michael, Ghosh, Samrat, Jakoby, Marius, Chen, Hongye, Ghalami, Farhad, Xie, Weiwei, Heidrich, Shahriar, Tsutsui, Yusuke, Freudenberg, Jan, Seki, Shu, Howard, Ian A., Richards, Bryce S., Bunz, Uwe H. F., Elstner, Marcus, Wenzel, Wolfgang, Wöll, Christof
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society of Chemistry 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8179632/
https://www.ncbi.nlm.nih.gov/pubmed/34168750
http://dx.doi.org/10.1039/d0sc07073d
Descripción
Sumario:Charge carrier mobility is an important figure of merit to evaluate organic semiconductor (OSC) materials. In aggregated OSCs, this quantity is determined by inter-chromophoric electronic and vibrational coupling. These key parameters sensitively depend on structural properties, including the density of defects. We have employed a new type of crystalline assembly strategy to engineer the arrangement of the OSC pentacene in a structure not realized as crystals to date. Our approach is based on metal–organic frameworks (MOFs), in which suitably substituted pentacenes act as ditopic linkers and assemble into highly ordered π-stacks with long-range order. Layer-by-layer fabrication of the MOF yields arrays of electronically coupled pentacene chains, running parallel to the substrate surface. Detailed photophysical studies reveal strong, anisotropic inter-pentacene electronic coupling, leading to efficient charge delocalization. Despite a high degree of structural order and pronounced dispersion of the 1D-bands for the static arrangement, our experimental results demonstrate hopping-like charge transport with an activation energy of 64 meV dominating the band transport over a wide range of temperatures. A thorough combined quantum mechanical and molecular dynamics investigation identifies frustrated localized rotations of the pentacene cores as the reason for the breakdown of band transport and paves the way for a crystal engineering strategy of molecular OSCs that independently varies the arrangement of the molecular cores and their vibrational degrees of freedom.