P-type CuInSe₂ thin films prepared by selenization of one-step electrodeposited precursors

In this study, p-type CuInSe₂ (CIS) films were prepared by selenization of one-step electrodeposited Cu-In-2Se (atomic ratio) precursors. To obtain high-quality, dense, and homogeneous CIS films for solar cell application, the effects of substrate temperatures during selenization and precursor compositions on the final microstructures were systematically investigated. The precursor layers evolved in very different ways under different selenization conditions. The final microstructures and phases of the films depended critically on the precursor compositions, selenization temperature, and the selenization thermal process history. Low melting temperature Cu_xSe phase, which tended to segregate at the film surface, can efficiently assist the CIS grain growth. Large hexagonal CuSe platelets were formed at a temperature as low as 170 °C in Cu-rich precursor, which acted as an element-transport flux agent at higher temperature under high Se vapor and reacted with In-Se selenide to form CIS at temperatures above 500 °C. Good crystalline quality chalcopyrite CIS film was obtained at a selenization temperature of 550 °C.