Triangle islands and cavities on the surface of evaporated Cu(In, Ga)Se2 absorber layer

► Lots of uncommon triangle islands and cavities are found on (1 1 2) planes terminated by Se atoms of evaporated Cu(In, Ga)Se2 thin films. ► Se ad-dimer as a nucleus, Cu atom diffusion from Cu(In, Ga)Se2 grains brings the epitaxial triangle island. ► The triangle islands grow with a two-dimensional layered mode. ► The triangle cavities are formed due to the insufficient coalescence of triangle islands. ► The performance of solar cell without triangle islands is improved.