Step h: as shown in FIG. 8, the pixel definition layer transitional pattern 8 and the common layer may be heated. At the region A, the second dam member 511 is indented inward, so the third dam member 61 arranged on the second dam member 511 and the common layer on the third dam member 61 may be suspended in the midair. During the heating, the melted third dam member 61 and the melted common layer may flow downward, so as to remove the undercut at the lateral surface of the pixel definition layer transitional pattern 8, thereby to form the pattern 81 of the pixel definition layer with a gentle lateral surface.

The pixel definition layer transitional pattern 8 and the common layer may be heated under a specific condition, e.g., at a temperature of 80° C. to 100° C., or less, for 12 to 48 hours, especially at a temperature of 95° C. for 24 hours. After the heating, as shown in FIG. 8, the region A may become a region B, and the pixel definition layer transitional pattern 8 may become the pattern 81 of the pixel definition layer with a smooth slope as the lateral surface. It should be appreciated that, although the lateral surface of the pattern 81 of the pixel definition layer is the smooth slope, through controlling the heating temperature and the heating time period, a portion of the common layer at a top surface of the pattern 81 of the pixel definition layer may not be connected to the portion of the common layer at the pixel region.