Supporting Information

The supplementary material contains Pump beam images and Gaussian fitting (Fig. S1). A description of the arithmetic logic of singular value decomposition (SVD) is also included. Singular value histograms and DAS plots (Fig.S2), TAS obtained at different test sites of the internal and boundary region of the grains (Fig. S3 and S4), Carrier dynamic lifetimes corresponding to three test regions of the grain boundary (Table S1) and their dynamic process of PB signals (Fig. S5) are also included in the supplementary material.