Based on the data of growth of literature in the field of solar power, the present paper investigates the stage of evolution at which the scattering of articles over journals is similar to Bradford's curve, i.e. the stage at which Bradford's law is valid. Traces the related changes that take place in the size and elements of the core during the evolution and growth of literature. The study reveals that a curve similar to Bradford's curve is obtained when the field matures. The finding has been supported with the help of a simple mathematical model.