Growth kinetics, properties, performance, and stability of atomic layer deposition Zn-Sn-O buffer layers for Cu(In,Ga)Se2 solar cells

A new atomic layer deposition process was developed for deposition of ZnSnO buffer layers for Cu(In,Ga)Se2 solar cells with tetrakis(dimethylamino) tin, Sn(N(CH3)2)4, diethyl zinc, Zn(C2H5)2, and water, H2O. The new process gives good control of thickness and [Sn]/([Sn]?+?[Zn]) content of the films. The ZnSnO films are amorphous as found by grazing incidence X-ray diffraction, have a high resistivity, show a lower density compared with ZnO and SnOx, and have a transmittance loss that is smeared out over a wide wavelength interval. Good solar cell performance was achieved for a [Sn]/([Sn]?+?[Zn]) content determined to be 0.150.21 by Rutherford backscattering. The champion solar cell with a ZnSnO buffer layer had an efficiency of 15.3% (Voc?=?653?mV, Jsc(QE)?=?31.8?mA/cm2, and FF?=?73.8%) compared with 15.1% (Voc?=?663?mV, Jsc(QE)?=?30.1?mA/cm2, and FF?=?75.8%) of the best reference solar cell with a CdS buffer layer. There is a strong light-soaking effect that saturates after a few minutes for solar cells with ZnSnO buffer layers after storage in the dark. Stability was tested by 1000?h of dry heat storage in darkness at 85?degrees C, where ZnSnO buffer layers with a thickness of 76?nm retained their initial value after a few minutes of light soaking. Copyright (c) 2011 John Wiley & Sons, Ltd.