High-efficiency copper indium gallium diselenide (CIGS) solar cells with indium sulfide buffer layers deposited by atomic layer chemical vapor deposition (ALCVD)

This paper presents optimization studies on the formation of indium sulfide buffer layers for high-efficiency copper indium gallium diselenide (CIGS) thin-film solar cells with atomic layer chemical vapour deposition (ALCVD) from separate pulses of indium acetylacetonate and hydrogen sulfide. A parametric study of the effect of deposition temperature between 160degrees and 260degreesC and thickness (15-30 nm) shows an optimal value at about 220degreesC for a layer thickness of 30 nm, leading to an efficiency of 16.4%. Analysis of the device shows that indium sulfide layers are characterised by an improvement of the blue response of the cells compared with a standard CdS-processed cell, due to a high apparent band gap (2.7-2.8 e V), higher open-circuit voltages (up to 665 m V) and fill factor (78%). This denotes high interface quality. Atomic diffusion processes of sodium and copper in the buffer layer are demonstrated. Copyright (C) 2003 John Wiley Sons, Ltd.