The time-dependent wavepacket diffusive method(1)is extended to investigate the energy relaxation and separation of a hot electron-hole pair in organic aggregates with incorporation of Coulomb interaction and electron-phonon coupling.The pair initial condition generated by laser pulse is represented by a Gaussian wavepacket with central momentum.The results reveal that the hot electron energy relaxation is very well described by two-rate processes with the fast rate much larger the slow one,consistent with experimental observations,an effective electron-hole separation is accomplished accompanying the fast energy relaxation.Furthermore,although the extra energy indeed helps the separation by overcoming the Coulomb interaction,the width of initial wavepacket is much sensitive to the separation efficiency and the narrow wavepacket generates the more separated charges.This behavior may be useful to understand the experimental controversy of the hot carrier effect on charge separation.