Presentation Information
[17a-PB2-6]Unique Charge Localization and Charge Carrier Mobility in Amorphous Organic Semiconductors
Yuto Harima1, 〇Hiroyoshi Naito1,2,3, Yuki Mitsuta1,2, Toshio Asada1,2 (1.Osaka Metro. Univ., 2.RIMED, 3.Ritsumeikan RISA)
Keywords:
Kinetic Monte Carlo simulation,unique charge localization,amorphous organic semiconductors
The impact of charge localization on charge carrier mobility in amorphous organic semiconductors was investigated using a multiscale simulation approach combining molecular dynamics (MD), quantum chemical calculations, and kinetic Monte Carlo (KMC) simulations. An amorphous molecular aggregate consisting of 613 TCTA molecules was constructed by MD simulations employing the Amber GAFF force field. Site energies, electronic couplings, and density of states were evaluated by quantum chemical calculations, and charge transfer rates were determined based on Marcus theory.The simulations revealed a characteristic charge localization phenomenon in which a charge repeatedly shuttles between adjacent molecular pairs with high frequency. This localized motion, referred to as a shuttling trap, was clearly visualized using bubble plots representing charge hopping events within the molecular aggregate. KMC simulations of transient photocurrent demonstrated that such shuttling traps significantly suppress the hole drift mobility.To clarify the influence of shuttling traps, KMC simulations were performed with a constraint preventing the charge from returning to the immediately previous molecule. Under this condition, localized hopping events disappeared, charge transport pathways became more diverse, and the hole mobility increased markedly. These results indicate that shuttling-induced localization plays a crucial role in limiting charge transport in amorphous organic semiconductors and should be considered as an intrinsic transport-limiting mechanism.