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Sodium Effects on the Diffusion, Phase, and Defect Characteristics of Kesterite Solar Cells and Flexible Cu 2 ZnSn(S,Se) 4 with Greater than 11% Efficiency
Author(s) -
Yang KeeJeong,
Kim Sammi,
Kim SeYun,
Son DaeHo,
Lee Jaebaek,
Kim YoungIll,
Sung ShiJoon,
Kim DaeHwan,
Enkhbat Temujin,
Kim JunHo,
Kim Juran,
Jo William,
Kang JinKyu
Publication year - 2021
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202102238
Subject(s) - kesterite , materials science , diffusion , doping , layer (electronics) , chemical engineering , alloy , phase (matter) , solar cell , photovoltaics , alkali metal , nanotechnology , metallurgy , czts , photovoltaic system , optoelectronics , chemistry , thermodynamics , ecology , physics , organic chemistry , biology , engineering
Improving the efficiency of kesterite (Cu 2 ZnSn(S,Se) 4 ; CZTSSe) solar cells requires understanding the effects of Na doping. This paper investigates these effects by applying a NaF layer at various positions within precursors. The NaF position is important because Na produces Na‐related defects in the absorber and suppresses the formation of intrinsic defects. By investigating precursors with various NaF positions, the sulfo‐selenization mechanism and the characteristics of defect formation are confirmed. Applying a NaF layer onto a Zn layer in a CZTSSe precursor limits Zn diffusion and suppresses Cu‐Zn alloy formation, thus changing the sulfo‐selenization mechanism. In addition, the surface NaF layer provides reactive Se and S to the absorber layer by generating Na 2 Se x and Na 2 S x liquid phases during sulfo‐selenization, thus limiting the incorporation of Na into the absorber and reducing the Na effects. Efficiency values of 11.16% and 11.19% are obtained for a flexible CZTSSe solar cell by applying NaF between the Zn layer and back contact and between the Cu and Sn layers, respectively. This study presents methods for doping with alkali metals and improving the efficiency of photovoltaics.