Oxygen Promotes the Formation of MoSe₂ at the Interface of Cu₂ZnSnSe₄/Mo

Abstract

The contact, and thus the hole collection between Cu2ZnSnSe4 (CZTSe) and Mo, is a crucial issue to improve the performance of CZTSe solar cells. In this work, a method to improve the back contact is explored by spraying Na3PO4 on the surface of the Mo back contact. With the O provided from Na3PO4, extra MoO2 and MoO3 are formed at the surface of the back contact, and partial MoO2 is transformed into MoSe2 under high Se2 partial pressure during the selenization process. The formation of MoSe2 progresses from dispersed spots to a continuous layer but not from the reaction between CZTSe and Mo. Although a thick MoSe2 layer is formed, the CZTSe device performance increases from 7.2% to 8.3% on average. This study affords new insight into the formation of MoSe2, thus deeply strengthening the understanding of the back contact of kesterite solar cells and of two-dimensional chalcogenide devices.

Precursor solution chemistry via water additive enabling CZTSSe solar cells with over 12% efficiency

“…Nevertheless, the excessively loose film is not beneficial for selenization. On the one hand, Se vapor is easily penetrated into the film and reacts with the Mo layer to form a thick MoSe 2 layer, which will increase R s [31,32]. On the other hand, the penetrated Se facilitates the formation of a Cu 2−x Se fluxing agent at the bottom of the film and hence a double-large grain layer absorber structure finally form (Fig.…”

Sputtering of Molybdenum as a Promising Back Electrode Candidate for Superstrate Structured Sb2S3 Solar Cells

“…This is well consistent with Mo electrodes in substrate structured Sb 2 S 3 , as well as CIGS, CZTSSe solar cells. [ 21 ] The conductivity, one of the most appealing characters of the metal electrodes, is further explored on devices by a four‐point probe test (Figure 2b ). It is concluded that the square resistance of the Mo deposited on Sb 2 S 3 surface (5.6 Ω □ –1 ) is not distinctly different from that on the glass substrate (5.4 Ω □ –1 ) in the same thickness of ≈900 nm under the standard sputtering process.…”

Improvement of Performance of CZTSSe Solar Cells by the Synergistic Effect of Back Contact Modification and Ag Doping

“…Over 14% efficiency has been achieved for CZTSSe-based solar cells by regulating the phase evolution kinetics of Ag-doped CZTSSe in a positive pressure . In addition, to inhibit the carrier recombination at the back interface, numerous attempts of back interface engineering have been implemented. − For example, a TiN or Al 2 O 3 passivation layer was inserted between the CZTSSe absorber and Mo back electrode to prevent the formation of secondary phases in the absorber and reduce the thickness of MoSe 2 by inhibiting the interfacial reaction. A VSe 2 or MoO x − intermediate layer with high work function ( W F ) was inserted between the CZTSSe absorber and Mo back electrode to boost hole extraction and reduce the MoSe 2 thickness.…”