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

Chunkai Wang; Ting Wang; Yue Liu; Mengge Li; Ding Ma; Zhanhui Ding; Yan Zhu; Yuting Sun; Xiaofei Sun; Liyuan Shi; Ning Ding; Yongfeng Li; Bin Yao

doi:10.1021/acsami.4c02987

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

ACS Appl Mater Interfaces. 2024 May 22;16(20):26182-26194. doi: 10.1021/acsami.4c02987. Epub 2024 May 13.

Authors

Chunkai Wang^{1

2}, Ting Wang³, Yue Liu^{1

2}, Mengge Li^{1

2}, Ding Ma^{1

2}, Zhanhui Ding^{1

2}, Yan Zhu^{1

2}, Yuting Sun^{1

2}, Xiaofei Sun^{1

2}, Liyuan Shi^{1

2}, Ning Ding^{1

2}, Yongfeng Li^{1

2}, Bin Yao^{1

2}

Affiliations

¹ State Key Laboratory of Superhard Material, College of Physics, Jilin University, Changchun 130012, China.
² Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012, China.
³ College of Physical Science and Technology, Dalian University, Dalian 116622, China.

PMID: 38736356
DOI: 10.1021/acsami.4c02987

Abstract

To improve the performance of Cu₂ZnSn(S,Se)₄ solar cells, a strategy is proposed to improve the quality of absorber and back interface simultaneously by substituting V-doped Mo (Mo:V) for a conventional Mo back electrode and incorporating Ag into the Cu₂ZnSn(S,Se)₄ (ACZTSSe) absorber in this work. Since p⁺-type V-doped MoSe₂ (MoSe₂:V) is formed in the site between the absorber and Mo:V during selenization, the conventional Mo/n-MoSe₂ back contact is modified to Mo:V/p⁺-MoSe₂:V, a back surface passivation field (BSPF) is established at the back interface, the band bending of MoSe₂:V is downward and that of bottom of the absorber is upward. Further investigation reveals that the back contact modification and Ag doping have a synergistic effect on inhibiting carrier recombination, decreasing series resistance and increasing shunt resistance, thereby leading to the PCE of device without antireflection coating increased from 8.61 to 10.98%, which is larger than the sum of increase in PCE induced by Ag doping alone (8.61 to 9.66%) and back contact modification alone (8.61 to 9.63%). It is demonstrated that the synergistic effect stems mainly from the strengthened BSPF and the further reduced back contact barrier height. The former is due to the increased difference in work function (W_F) between MoSe₂:V and absorber induced by the reduced W_F of the absorber after Ag doping and the raised W_F of MoSe₂:V after V doping. The latter is due to the downshifted valence band maximum of absorber after Ag doping. This work highlights the synergistic effect of back contact modification and Ag doping on improving the performance of CZTSSe solar cells and also provides an effective way to suppress carrier recombination.

Keywords: Ag-doped Cu2ZnSn(S,Se)4; V-doped MoSe2; carrier recombination; field passivation; solar cells.