Predictive Model of Charge Mobilities in Organic Semiconductor Small Molecules with Force-Matched Potentials

Area of Science:

• Materials Science
• Computational Chemistry
• Solid-State Physics

Background:

• Charge mobility in crystalline organic semiconductors (OSCs) is significantly limited by local dynamic disorder.
• Accurate prediction of charge mobility in high-mobility OSCs, like TIPS-pentacene, has been achieved using density functional theory (DFT) simulations.
• However, the high computational cost of DFT calculations for atomic forces is a major limitation.

Purpose of the Study:

• To demonstrate the efficacy of density functional tight binding (DFTB) as a computationally efficient alternative to DFT for predicting charge mobility.
• To develop accurate DFTB models by force matching to DFT-derived forces for capturing dynamic disorder.
• To explore new structural analogues of TIPS-pentacene for potential applications in tailored OSCs.

Main Methods:

• Utilized density functional tight binding (DFTB), a semiempirical quantum mechanical method, for its significantly lower computational expense compared to DFT.
• Employed force matching to create accurate DFTB models by fitting to forces calculated from DFT.
• Integrated DFTB-derived dynamic disorder with transient localization theory to predict charge mobility.

Main Results:

• Developed highly accurate DFTB models that reproduce experimental inelastic neutron scattering (INS) spectra, particularly low-frequency features.
• Successfully predicted charge mobility with high accuracy using the developed DFTB models.
• Identified and simulated charge mobilities for previously unstudied structural analogues of TIPS-pentacene.

Conclusions:

• DFTB offers a computationally efficient and accurate pathway for simulating materials properties, specifically charge mobility in OSCs.
• The established approach enables rapid prediction of charge mobility, facilitating the design of novel OSCs with desired characteristics.
• This methodology holds significant potential for accelerating materials discovery in the field of organic electronics.