Preparation and Characterization of Silver‐Doped Cu(In,Ga)Se2 Films via Nonvacuum Solution Process
Cu(In,Ga)Se2 films doped with different contents of silver ions (Ag+) were successfully prepared using nonvacuum spin coating followed by selenization at elevated temperatures. Increasing the Ag+ ion content increased the lattice parameters of the chalcopyrite structure, and shifted the A1 mode in the Raman signals to low frequencies. The band gaps of the prepared (Ag,Cu)(In,Ga)Se2 (ACIGS) films were considerably increased, thereby increasing the open‐circuit voltage (V oc) of the solar cells. As Ag+ ion content increased, the microstructures of ACIGS films became densified because the formed (Cu,Ag)2In alloy phase with a low melting point facilitated liquid‐phase sintering. The evaporation of selenium species was correspondingly suppressed in the films during selenization, thereby reducing the selenium vacancies. The improvement in the microstructures and the defects of ACIGS films increased short‐circuit current (J sc) and fill factor of the solar cells. The spectral response of the solar cells was also enhanced remarkably. This study demonstrated that incorporation of Ag+ ions into Cu(In,Ga)Se2 films substantially improved the efficiency of the solar cells.
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