▎ 摘　　要

The problem of charge generation at short time scales in organic materials is of crucial importance for optoelectronics. Excluding controversial interpretations, the current state of the art suggests that highly delocalized photoexcitations enable the immediate probability of charge-transfer states within the ultrafast regime (similar to 100 fs). Here, we shed light on this problem by investigating the ultrafast direct generation of quasiparticles in armchair graphene nanoribbons (AGNRs). Through a two-dimensional tight-binding model that includes lattice relaxation effects, the direct creation mechanism of different quasiparticle species is elucidated. Results show that quasiparticles of distinct nature, namely solitons, polarons, and bipolarons, are directly formed in these materials within the ultrafast regime. The creation time for polarons depends on ribbon width and charge density, whereas for solitons and bipolarons only the former property plays a role. Our findings suggest that the creation times of these quasiparticles are quite different among nanoribbon families except under high charge carrier densities. These findings elucidate the assumption in the literature that charge carriers can be directly generated in organic materials within the ultrafast regime. (C) 2019 Elsevier Ltd. All rights reserved.