DC and RF sputtered molybdenum electrodes for Cu(In,Ga)Se2 thin film solar cells

Abstract

In this study, molybdenum (Mo) thin films are deposited at different working pressures and different target-substrate distances (Dt-s) (8 cm and 10 cm) under the excitation of the radio frequency (RF) or direct current (DC) power supply for applications in Cu(In,Ga)Se2 (CIGS) thin film solar cells. The various material properties including dynamic deposition rate, electrical and optical properties, crystal structure and morphology are systematically investigated and compared for these RF and DC sputtered Mo thin films. Mo bilayer, i.e. bottom Mo layer prepared at a high working pressure and top Mo thin film sputtered at a low working pressure are employed as back electrodes in CIGS thin film solar cells. CIGS thin film solar cells with DC Mo/DC Mo bilayer have relatively higher efficiency as compared to the others with RF Mo layers, which might be related to a relatively easy migration of sodium (Na) passing through the DC Mo layers and entering into the CIGS absorbers. A high efficiency CIGS thin film solar cell of 16.2% has been achieved in this work.