EFFECT OF THERMAL PROCESSING ON OPTICAL AND ELECTRICAL PROPERTIES OF COPPER SELENIDE THIN FILMS

V.M. García^*, L. Guerrero, M. T. S. Nair and P. K. Nair

Centro de Investigación en Energía, Universidad Nacional Autonoma de México, Temixco-62580, Morelos, MEXICO, mtsn@mazatl.cie.unam.mx

*Universidad Autónoma de Zacatecas, Facultad de Ciencias Químicas, Guadalupe, Zacatecas, MEXICO, vmgarcia@cantera.reduaz.mx

We report on the structural, optical and electrical properties of thin films of copper selenide obtained from chemical bath deposition and changes brought about in these properties during thermal treatment at 200ºC – 400ºC in air and vacuum. As-prepared CuSe thin films transform to Cu_2-xSe during vacuum annealing at 400ºC, where as, the composition of chemically deposited Cu_1.85Se films remains practically stable during such annealing. The high near infrared reflectance (30-80%) and low transmittance of the films are related to a high p-type electrical conductivity ~ (1-5) 10³ ^-1cm^-1 of these films. A theoretical fit is made to the experimental transmittance and reflectance curves based on free carrier optical absorption. Thermal processing of Cu_2-xSe-In and CuSe-In films, with vacuum evaporated In film (20 – 40 nm) results in partial conversion of the films to Cu_xIn_ySe_z. Applications of the films in automotive window coatings and photovoltaic conversion are suggested.