Over 10% efficient Cu2ZnSn(S, Se)4 Thin-Film cells prepared by aluminium doping

Abstract

Cu2ZnSn(S,Se)4(CZTSSe) solar cell is of excellent development tendency because of lower pollution and outstanding power conversion efficiency(PCE). Yet, current PCE of CZTSSe is limited because of a high open-circuit voltage deficit, primarily put down to severe band tailing and carrier recombination. In this paper, absorber films were obtained by solution method and the influences of different aluminum doping concentrations on the properties of CZTSSe thin film cell were studied. Analysis about X-ray diffraction (XRD) and Raman spectroscopy confirms which Al has incorporated into CZTSSe thin film lattice and replaced Sn. Hall effect measurements reveal the improvement of carrier concentration on thin film absorber layer attribute to the formation of AlSn acceptor defects. Furthermore, X-ray photoelectron spectroscopy (XPS) reveals that Al enter into the CZTSSe lattice and Al is in the appropriate state of + 3 valence without generating additional harmful defects. More important, the generation of deep energy level defects and defect clusters associated with Sn were suppressed by replacing Sn with Al. Finally, the photovoltaic performance of different Al doped CZTSSe cells were characterized by conducting J-V and external quantum efficiency (EQE) tests. Remarkably, the CZTSSe solar cell with PCE as high as 10.59 % is obtained under a doping level of 6 % Al, which has an open circuit voltage of 522 mv. Compared with reference CZTSSe solar cells with an efficiency of 7.29 %, which indicates with improvement of 45 % in efficiency. Consequently, Al doping process is considered as a prospective tactic to elevate the PCE of CZTSSe solar cells.