Studies on monocrystalline CuInSe2 and CuIn3Se5

Crystalline ingots of composition CuIn3Se5 corresponding to the reported ordered vacancy compound (OVC), were grown by a horizontal Bridgman method. X-ray powder diffraction measurements showed the characteristic peaks of this material: (002), (110), (200)/(004), (202) and (114). From these results, lattice constants were calculated to be n = 5.759 Angstrom and c = 11.524 Angstrom. Mall effect measurements were made on this material indicating that it is n-type with a carrier concentration of about 10(9) cm(-3) and a mobility of around 200 cm(2)/(V s). The CuIn3Se5 material was found to be strongly photoconductive over the wavelength range from 600 to 1100 nm. Since the formation of the OVC is reported to exist only within the surface layer of the chalcopyrites, some studies were initiated on the surface composition determination of monocrystalline CuInSe2. In photovoltaic cells using monocrystalline CuInSe2 as a substrate, it was found earlier, in this laboratory, that pre-annealing the substrate in argon at 350 degrees C for about 2 h improved photovoltaic performance. Measurements of Auger profiles in the first 200 Angstrom or so of annealed and unannealed monocrystalline samples indicate no evidence of the formation of an OVC near the surface during the heat-treatment process. (C) 2000 Elsevier Science S.A. All rights reserved.