title: Growth of Cu2ZnSnSe4 Film under Controllable Se Vapor Composition and Impact of Low Cu Content on Solar Cell Efficiency.
abstract: It is a challenge to fabricate high quality Cu2ZnSnSe4 (CZTSe) film with low Cu content (Cu/(Zn + Sn) < 0.8). In this work, the growth mechanisms of CZTSe films under different Se vapor composition are investigated by DC-sputtering and a postselenization approach. The composition of Se vapor has important influence on the compactability of the films and the diffusion of elements in the CZTSe films. By adjusting the composition of Se vapor during the selenization process, an optimized two step selenization process is proposed and highly crystallized CZTSe film with low Cu content (Cu/(Zn + Sn) = 0.75) is obtained. Further study of the effect of Cu content on the morphology and photovoltaic performance of the corresponding CZTSe solar cells has shown that the roughness of the CZTSe absorber film increases when Cu content decreases. As a consequence, the reflection loss of CZTSe solar cells reduces dramatically and the short circuit current density of the cells improve from 34.7 mA/cm(2) for Cu/(Zn + Sn) = 0.88 to 38.5 mA/cm(2) for Cu/(Zn + Sn) = 0.75. In addition, the CZTSe solar cells with low Cu content show longer minority carrier lifetime and higher open circuit voltage than the high Cu content devices. A champion performance CZTSe solar cell with 10.4% efficiency is fabricated with Cu/(Zn + Sn) = 0.75 in the CZTSe film without antireflection coating.
authors.affiliation: Institute of Photoelectronic Thin Film Devices and Technology, Nankai University , Tianjin 300071, P.R. China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology , Brisbane, Queensland QLD4001, Australia.
authors.forename: Hongxia
authors.initials: H
authors.lastname: Wang
authors.affiliation: The MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University , Tianjin 300457, China.
authors.forename: Li
authors.initials: L
authors.lastname: Wu
authors.affiliation: Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology , Wuhan, Hubei 430074, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.affiliation: Institute of Photoelectronic Thin Film Devices and Technology, Nankai University , Tianjin 300071, P.R. China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Institute of Photoelectronic Thin Film Devices and Technology, Nankai University , Tianjin 300071, P.R. China.
authors.forename: Fangfang
authors.initials: F
authors.lastname: Liu
authors.affiliation: Institute of Photoelectronic Thin Film Devices and Technology, Nankai University , Tianjin 300071, P.R. China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology , Wuhan, Hubei 430074, China.
authors.forename: Junbo
authors.initials: J
authors.lastname: Han
authors.affiliation: Institute of Photoelectronic Thin Film Devices and Technology, Nankai University , Tianjin 300071, P.R. China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
keywords: CZTSe; Cu content; SnSe2 phase; selenization; textured surface