TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Method: The layers are deposited by electrodeposition. The second and intermediate layers have been treated to enhance its n-type electrical conductivity. The second semiconductor layer has been treated to increase the height of the Schottky barrier at the interface between the second semiconductor layer and the metal contact. It is treated by pinning the Fermi energy level of the second layer below the conduction band minimum and closer to the valence band maximum.Preferred Component: An n-n heterojunction is required within the device. A large Schottky barrier is required at the metal-second semiconductor thin film interface. A protective layer is provided between the back metal contact and the second photon absorber layer to prevent reaction between the second semiconductor material and the metal. The device comprises a multi-layer graded band gap structure.Preferred Property: The Fermi energy level is pinned at the largest predetermined energy level positions, preferably 0.96 most preferably 1.18 eV. The semiconductor material comprises defect levels due to addition of impurities or native defects configured to enable capture of low energy infrared electromagnetic radiation having energy of less than 1.45 eV.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The enhancement of the n-type electrical conduction is due to n-type doping. It involves treatment with cadmium chloride, cadmium iodide, or cadmium bromide. The second semiconductor layer is doped with an impurity comprising iodine, bromine, or chlorine atoms. The layers are heated in air 250-500 preferably 450 degrees C for 20 minutes. The device is treated to encourage mixing of the semiconductor layer materials at the boundaries of the layers. The outer surface of the second semiconductor material has been chemically etched.Preferred Material: Each semiconductor layer comprises cadmium. The window layer comprises n-type cadmium sulfide. The window layer comprises n-type zinc selenide. The intermediate layer comprises n-type cadmium selenide. The outermost second semiconductor layer comprises cadmium telluride.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The protective layer comprises an organic polymer, an inorganic fluoride layer or a p-type conducting polymer.