Solar cell technologies, using I-III-VI2 direct band-gap chalcopyrite semiconductors as the absorber layer, have attracted great interest [1]. CuInSe2-based solar cells are currently demonstrating the leading performance amongst thin-film technologies. One way of boosting the performance of solar cells consists in coating them with a textured layer. Electrochemical treatment proved to be a powerful tool for the preparation of a variety of porous morphologies. The goal of this report is to demonstrate that electrochemical treatment can be also applied for nanostruturing of CuInSe2 crystals, particularly for patterning the surface of the samples to reduce the reflection at the surface in the case of their implementation in solar cells. It was found that CuInSe2 crystals can be nanostructured by electrochemical treatment in an aqueous HCl solution. In order the crystals to become suitable for electrochemical nanostructuring they are subjected to thermal treatment either in vacuum or in Zn vapors as shown in Table 1. Table 1. Electrical parameters of CuInSe2 crystals subjected to different thermal treatmenttableThe morphology of the produced material and the diameter of pores are found to be a function of the resistivity of samples attained after thermal treatment (Fig. 1). The pore diameter can vary in the range from 100 nm to 1 μm. The influence of thermal treatment and electrochemical etching on the photoluminescence spectra is analyzed.figureFig. 1. SEM images of surfaces of CuInSe2 crystals with numbers #5 (a) #4 (b) and #3 (c) in Table 1 subjected to electrochemical treatment at 0.7 V in an aqueous HCl electrolyte.