Limits for short-pulse laser processing of high efficiency crystalline silicon solar cells on thin wafers

We show that laser processing on one side of a silicon wafer can lead to a significant damaging of the opposite side, dependent on the wafer thickness and the topography of the surface that is opposed to the laser-processed side. We find that laser pulse energies in the range of the ablation threshold of dielectric layers can result in a degradation of the front side of wafers thinner than 120 µm. Increasing the laser pulse energy density beyond values that we typically use for dielectric layer ablation results for thin wafers in optically visible removal of the front side passivation.