Time-Domain Ab Initio Study of Nonradiative Decay in a Narrow Graphene Ribbon

We investigate nonradiative decay ill the (16,16) armchair graphene nanoribbon (GNR) using surface-hopping with decoherence in a time-dependent Kohn-Sham scheme, The lowest singlet excitation decays within 300 ps in the ideal GNR by coupling to the 1450 cm(-1) disorder mode associated with edges. The C-2-insertion defect doubles the decay rate. Compared to carbon nanotubes (CNTs), GNRs are more anharmonic and show faster phonon-induced pure dephasing of electronic transitions. Defects relieve strain better and, therefore, exhibit weaker electron-phonon coupling in GNRs than CNTs. The slower nonradiative decay of GNRs compared to similar size CNTs makes GNRs better candidates for the semiconductor applications.