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Abstract Organic semiconductors (OSCs) have garnered significant attention due to their potential use in flexible, lightweight, and cost‐effective electronic devices. Despite their promise, the assembly of organic molecules into the condensed phase promotes a diverse set of lattice dynamics that introduce a detrimental modulation in the intermolecular electronic structure—termed dynamic disorder—that results in charge carrier mobilities that are orders of magnitude lower than inorganic semiconductors. This dynamic disorder is generally associated with low‐frequency phonons, yet whether a small subset of modes or a broad range of phonons  drives dynamic disorder remains contested. Resolving this debate is critical for defining how targeted phonon engineering could practically improve OSC performance. In this review, we explore progress toward uncovering the interplay between lattice dynamics and charge transport in OSCs, focusing on the critical role of thermally activated phonons. We describe the powerful insight that mode‐resolved analyses of electron–phonon interactions lends toward the rational design of new materials. We highlight recent efforts to achieve this, showcasing proposed strategies to mitigate dynamic disorder through molecular and crystal design. This work offers an overview of the insight gained toward understanding the fundamental mechanisms governing charge transport in OSCs and outlines pathways for enhancing performance via targeted manipulation of interatomic/intermolecular interactions and resulting phonon modes. 

Abstract Organic semiconductors with distinct molecular properties and large carrier mobilities are constantly developed in attempt to produce highly‐efficient electronic materials. Recently, designer molecules with unique structural modifications have been expressly developed to suppress molecular motions in the solid state that arise from low‐energy phonon modes, which uniquely limit carrier mobilities through electron–phonon coupling. However, such low‐frequency vibrational dynamics often involve complex molecular dynamics, making comprehension of the underlying electronic origins of electron–phonon coupling difficult. In this study, first a mode‐resolved picture of electron–phonon coupling in a series of materials that are specifically designed to suppress detrimental vibrational effects, is generated. From this foundation, a method is developed based on the crystalline orbital Hamiltonian population (COHP) analyses to resolve the origins—down to the single atomic‐orbital scale—of surprisingly large electron–phonon coupling constants of particular vibrations, explicitly detailing the manner in which the intermolecular wavefunction overlap is perturbed. Overall, this approach provides a comprehensive explanation into the unexpected effects of less‐commonly studied molecular vibrations, revealing new aspects of molecular design that should be considered for creating improved organic semiconducting materials. 

Comparison of the optical properties of Co₃O₄and ZnCo₂O₄elucidates fundamental differences in mechanisms of photoinduced polaron formation based on the presence or absence of substitutional lattice defects arising from cation inversion. 

We investigate the anisotropic thermal expansion behavior of a co- crystalline system composed of 4,40-azopyridine and trimesic acid (TMA-azo). Using variable-temperature single-crystal X-ray diffrac- tion (SC-XRD), low-frequency Raman spectroscopy, and terahertz time-domain spectroscopy (THz-TDS), we observe significant temperature-induced shifting and broadening of the vibrational absorption features, indicating changes in the intermolecular potential. Our findings reveal that thermal expansion is driven by anharmonic interactions and the potential energy topography, rather than increased molecular dynamics. Density functional the- ory (DFT) simulations support these results, highlighting significant softening of the potential energy surface (PES) with temperature. This comprehensive approach offers valuable insights into the relationship between structural dynamics and thermal properties, providing a robust framework for designing materials with tailored thermal expansion characteristics.