“…Regardless of the wavelength, intensity, and location of radiation hitting the structures, the layer is always positively charged, which reflects the nature of the change in the composition of the near-surface region of the crystal as a result of heat treatment. Since the role of acceptor-type intrinsic defects in CuInSe2 is played by vacancies in the copper sublattice and oxygen introduced during heat treatment leads to a decrease in the concentration of donor levels [15,17,18], as a result of the studied heat treatment regimes, an increase in the degree of compensation of CuInSe2 in the near-surface region is achieved and causes the formation of an isotypic n -n+ -transition [19,20].…”