This application provides an A/M/X crystalline material, a photovoltaic device, and preparation methods thereof. The photovoltaic device includes a photoactive crystalline material layer. The photoactive crystalline material layer includes a penetrating crystal, where the penetrating crystal is a crystal penetrating through the photoactive crystalline material layer, and a percentage p of a quantity of penetrating crystals in a total quantity of crystals of the photoactive crystalline material layer is ≥80%. The photoactive crystalline material layer includes a backlight side and a backlight crystal, where the backlight crystal is a crystal exposed to the backlight side and has a backlight crystal face exposed to the backlight side. At least one region of the backlight side has an average flatness index R avg being ≤75.