The optoelectronic properties of doped with Cl CdTe thin films, thick layers and monocrystals have been investigated. It has been shown that high resistance, high photoconductivity or high p-type conductivity can be formed in doped only with Cl CdTe, depending on the Cl concentration. It has been supposed that a too high Cl concentration in recrystallized with CdCl₂ flux CdTe film has been one of the key efficiency limits of CdTe-based solar cells.