Ag(In1-xGax)Se2 thin films have been deposited on Mo-coated soda-lime glass substrates by the three-stage process using a molecular beam epitaxy (MBE) system. We found a remarkable decrease in the substrate temperature during the 2nd stage in which the film composition changes to a Ag excess. A single phase chalcopyrite AIGS thin film with a slightly Ag poor composition was obtained by using the temperature monitoring composition method. The cell performance of the AIGS thin film solar cell was found to strongly depend on the Ga/(In+Ga) and Ag/(In+Ga) atomic ratios.
A high efficiency wide-gap (Eg=1.7eV) Ag(In0.2Ga0.8)Se2 thin film solar cell with a total-area efficiency of 9.3% (10.2% active area efficiency), Voc = 949mV, Jsc = 17.0 mA/cm2, FF = 0.577, and total area = 0.42 cm2 was achieved. The junction formation mechanism of AIGS devices is discussed based on electron beam induced current (EBIC) and scanning capacitance microscopy (SCM) analyses.