We have studied numerically the time-dependent photon-assisted tunneling (TD-PAT) process for electrons confined in quantum dots (QDs) by employing the finite difference method under the scheme of the TD-density functional theory (DFT). We have found the quasi-dark state (quasi-DS), where the injected electron remains in the QD. By varying the barrier thickness, we have calculated the TD profile of the electron density in a QD, and found the optimal geometry of the lozenge QD. We have also discussed how the charged QD modulates the PAT process.