Growth of Cu2ZnSnSe4 Film under Controllable Se Vapor Composition and Impact of Low Cu Content on Solar Cell Efficiency

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• 作者：Jianjun Li ; Hongxia Wang ; Li Wu ; Cheng Chen ; Zhiqiang Zhou ; Fangfang Liu ; Yun Sun ; Junbo Han ; Yi Zhang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：April 27, 2016
• 年：2016
• 卷：8
• 期：16
• 页码：10283-10292
• 全文大小：797K
• 年卷期：0
• ISSN：1944-8252

文摘

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/cm² for Cu/(Zn + Sn) = 0.88 to 38.5 mA/cm² 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.